2 The CDF Experiment at Fermilab Contents - Harvard University ...

1
2 The CDF Experiment at Fermilab
Faculty: Melissa Franklin, John Huth, Michael Schmitt; Postdocs: Kevin Burkett, Tommaso
Dorigo, Petar Maksimovic, Werner Riegler; Graduate students: Stephen Bailey,
Carter Hall, Ayana Holloway, Robyn Madrak, David Medvigy, Maria Spiropulu, Melissa Wessels
Contents
2 The CDF Experiment at Fermilab 1
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.2 Hardware Upgrade Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Central Outer Tracker (COT) . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2 Data Acquisition for the Silicon Vertex Detector (SVX) . . . . . . . . 20
2.2.3 Central Muon Extension (CMX) . . . . . . . . . . . . . . . . . . . . . 26
2.3 Run I Physics Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.3.1 Search for Supersymmetric Quarks and Gluons (~q, ~g) . . . . . . . . . 37
2.3.2 The Top Quark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.3.3 The W Mass Measurement . . . . . . . . . . . . . . . . . . . . . . . . 54
2.3.4 Study of the decay Z ! bb . . . . . . . . . . . . . . . . . . . . . . . . 63
2.4 Run II and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
2.4.1 Discovery Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
2.4.2 Di-Boson Production . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
2.4.3 Missing Transverse Energy + Jets . . . . . . . . . . . . . . . . . . . . 72
2.4.4 Missing Energy Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . 76
2.4.5 Multijet Trigger for W=Z + h . . . . . . . . . . . . . . . . . . . . . . 79
2.4.6 Di-Jet Mass Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . 86
2.4.7 B Mixing and CP Violation . . . . . . . . . . . . . . . . . . . . . . . 88
2.5 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2 Section 2: CDF
2.1 Introduction
The Fermilab TEVATRON has undergone major upgrades over the last three years. The
goal is an increase in the luminosity from approximately 1:610 31 cm ,2 sec ,1 achieved in the
past to 8:6 10 31 cm ,2 sec ,1 in the near future [1]. This increase of more than a factor of 5
follows from several major improvements in the accelerator, including an upgraded Linac, the
replacement of the Main Ring by the Main Injector, and the collection of unused antiprotons
by the Recycler. The last factor is particularly important since the generation of antiprotons
was and will continue to be the limiting factor in the luminosity. The ultimate luminosity
expected from these accelerator upgrades is expected to be as high as 1:6 10 32 cm ,2 sec ,1 .
The next collider run is scheduled to begin next year. On the basis of the projected
increases in luminosity, CDF anticipates collecting an event sample corresponding to 2 fb ,1
over two or three years, to be compared to the approximately 100 pb ,1 collected thus far.
Ultimately the TeVatron may deliver 20{30 pb ,1 over the next six or seven years.
The increase in luminosity requires major changes to the apparatus. The bunch spacing
will be reduced by about a factor of nine, to 396 ns. (In the high luminosity case of
10 32 cm ,2 sec ,1 , the bunch spacing would be further reduced to 132 ns.) As a consequence,
the data acquisition system must be replaced as the older system cannot handle
the rate. This provides an opportunity to modernize the system: a pipe-lined design has
been chosen which reduces the deadtime to essentially zero. Similarly, the central tracking
is inadequate and will be wholly replaced by a similar but substantially improved device.
At the same time the ducial coverage is signicantly increased. The inner tracking, based
on silicon strips, is much advanced over the previously very successful vertex detector: here
again the coverage is greatly increased, and for the rst time three-dimensional tracking will
be available. Furthermore, there will be the capability to use vertex tracking in the trigger,
which raises the possibility of trigger on b-quark jets. Finally, lepton identication is important
for physics analyses and also at the trigger level, so the muon system is being improved,
and the forward calorimetry will be replaced allowing better coverage for electrons.
The Harvard group is involved in three of the major upgrades projects for CDF: the
Central Outer Tracker (COT), the Silicon Vertex Detector (SVX) and the Central Muon
Extension (CMX). Our hardware activities are exciting and serve to educate our students
well and to provide opportunities for our post-docs to play leading roles inside the collaboration.
At the same time, we continue to play an important role in some of the remaining analyses

Section 2: CDF 3
of Run I data. Recently, though, we have begun to organize our analysis resources towards
the future.
Analysis projects have progressed since the last review. Andrew Gordon completed
his measurements of the W mass and a long publication will be nished this summer.
Maria Spiropulu has pursued the search for new physics in events with jets and signicant
missing energy, and an exciting new result is expected in the upcoming months. Stephen
Bailey continues to develop his strategies for measuring the CP violation parameter with
the Run II data. Robyn Madrak and Carter Hall are starting analyses in diboson production
which could provide a result for their theses.
There are new students who are working actively on CDF hardware and/or analysis,
including Ayana Holloway, Melissa Wessels and David Medvigy.
Tommaso Dorigo joined our group as a post-doc at the beginning of the year. He plays
the central role in the CMX and is active in several analyses areas. Last year he completed
his Ph.D. with the University of Padova.
A summary of present personnel is given in Table 1.

4 Section 2: CDF
name rank starting date major activities on CDF
Stephen Bailey student 1997 CP violation; SVX DAQ
Kevin Burkett post-doc 1998 Higgs and SUSY; COT
Tommaso Dorigo post-doc 1999 electroweak & Higgs; CMX
Melissa Franklin professor 1987 top, W, Higgs, searches; COT
Andrew Gordon student 1993 W mass (thesis: 1998)
Carter Hall student 1997 W decays; COT
Ayana Holloway student 1998 searches
John Huth professor 1993 SUSY & Higgs; SVX DAQ
Robyn Madrak student 1997 diboson production; COT
Petar Maksimovic post-doc 1997 B mixing, CPV, Higgs; SVX DAQ
David Medvigy student 1998 searches
Werner Riegler post-doc 1997 Higgs; COT
Michael Schmitt assist. prof. 1998 Higgs, searches; CMX
Maria Spiropulu student 1995 SUSY
Melissa Wessels student 1998 searches; COT
Table 1: Personnel in the Harvard CDF Group and their current activities. See page 102
for a list of students who have completed their theses.

Section 2: CDF Hardware Projects 5
2.2 Hardware Upgrade Projects
The upgrades of the CDF apparatus are substantial. All of the tracking is being replaced,
and the Harvard group is involved in the two most important tracking subsystems: the
Central Outer Tracker (COT) and the Silicon Vertex detector (SVX). It also carries
full responsibility for the Central Muon Extension (CMX) which it built as an upgrade
to the muon system during Run I. Each of these projects is described below.
Much of the success of these undertakings is attributable to the excellent support sta
Harvard enjoys. John Oliver and Nathan Felt are responsible for the design of many important
electronics modules and systems, in particular, for parts of the data acquisition system
for the SVX. Jack O'Kane and Sarah Harder fashioned quickly and reliably many of the
boards and electronic devices needed by the Harvard CDF group. The skills and dedication
of Rick Haggerty and Steve Sansone in the machine shop guarantee the success of the COT
project of the CMX.
2.2.1 Central Outer Tracker (COT)
(Prof. Franklin, Dr. Burkett, Dr. Riegler, Mr. Hall, Ms. Madrak & Ms. Wessels)
Overview of Central Outer Tracker
CDF is upgrading detectors and electronics to handle luminosities higher than in previous
runs. The higher luminosity will be achieved by both increasing the number of proton
bunches, and by using a more ecient injector (the Main Injector) to the superconducting
synchrotron. At the beginning of Run II, the bunches will cross at CDF every 396 ns, and
in Run IIb, every 132 ns. The central tracking chamber in CDF Run 1 was known as the
CTC. The upgraded design, the Central Outer Tracker (COT), is similar to the CTC but
improves upon identied deciencies and accommodates the higher luminosity of Run II.
The maximum drift time has been reduced from 706 ns to 100 ns which means that events
will not overlap in the chamber. This is accomplished both by reducing the maximum drift
distance from 3.6cm to 0.88cm and by using a faster gas, Argon-Ethane-CF 4 (50:35:15).
The number of stereo layers has been increased from 24 to 48, which will improve tracking
resolution in the r , z plane. The CTC was segmented into nine super-layers, ve axial and
four stereo. The ve axial super-layers consisted of 12 sense wire layers, while the four
stereo super-layers consisted of only 6 sense wire layers. Thus there were only 24 stereo

6 Section 2: CDF Hardware
Au mylar
sense wire
support wire
potential wire
Figure 1: em COT cell geometry
measurements, out of 84 total. This meant rst that the stereo view could not be completed
without an externally supplied z 0 . In addition, at high luminosity the occupancy caused
a signicant loss of eciency in the innermost superlayers, resulting in a decrease in the
3D track reconstruction eciency. Various dierences between the CTC and the COT are
revealed in Table 2.
The COT is segmented into 8 super-layers alternating stereo and axial, with a stereo
angle of 2 . Both axial and stereo super-layers contain 12 sense wires alternated with 13
potential wires which provide the eld shaping within the cell as shown in Fig. 1. Whereas
the CTC used wires between the cells to complete the eld regions, this is accomplished in
the COT by gold-coated Mylar sheets. This gives a more uniform drift eld and reduces both
the overall mass of the chamber and the tension on the endplates. Roughly 1500 eld sheets
for the stereo super-layers were produced at Harvard, while some 1700 axial eld sheets were
produced at Lawrence Berkeley National Laboratory. The sense wire planes were built at
Fermilab.
Field Sheet Construction
The construction of the eld sheets was undertaken at Harvard by one professor, Melissa
Franklin, one post-doc, Kevin Burkett, three graduate students, Carter Hall, Robyn Madrak
and Melissa Wessels, 5 undergraduates, Tobias Jacoby, Sarah Demers, Caolionn O'Connell,

Section 2: Central Outer Tracker 7
CTC COT
Max Drift Time 706 ns 100 ns
Max Drift Distance 3.6 cm 0.88 cm
Total Layers 84 96
Total Sense Wires 6156 30240
# Axial Layers 60 48
# Stereo Layers 24 48
Radiation Lengths 1.7% 1.3%
Table 2: Comparison of mechanical design parameters of the CTC and COT.
Carina Curto, Sarah Fung, one technician, one machinist and three temps. The eld sheets
are 6.35 m Mylar coated with 450 A gold. The gold sheets are epoxied to aluminum
endboards which latch onto the endplates of the chamber. To maintain the atness of the
sheets, two 305 m (12 mil) stainless steel wires are epoxied along the edges of the sheets in
a parabolic shape. When the sheets are placed under tension, a fraction of the longitudinal
tension is transferred to lateral tension by the wires. We tried to make these eld sheets
as at as possible, given gravity. To maintain uniform gain, local variations in the shape of
the sheet, i.e. ripples, must be controlled. The sag of the sheet must also be controlled to
avoid excessive displacement of the sense wires when the High Voltage is turned on. Studies
of gain variation as a function of the amplitude of ripples in the sheet have shown that the
latter must be less than 10 mils. The average position of the sheet must be good to 5 mils to
minimize sense wire motion. Allowed variations in sheet length were kept small in order to
allow for an error in predicted endplate deection under tension. The allowed variations in
sheet length, as well as the number of sheets required in each stereo super-layer, are shown
in Table 3.
A test xture was built by Harvard that has been used to measure the length and the
shape of sheets under the nominal 22 lbs. of tension that will be applied in the chamber.
This same test xture was used at Berkeley. As it is dicult to dierentiate between sheet
sag and ripples in the test station, a 5 mil window is allowed for the shape of the sheet
in the test xture. All passing sheets fell within this window and had a measured length
which was within the allowed range for the superlayer in which they are used. Fig. 2 shows
distributions of the dierence between actual sheet length and desired length, in inches, for

8 Section 2: CDF Hardware
Super-Layer # Sheets Length Tolerance (In.)
1 185
3 264
5 370
7 476
+0:211
,0:005
+0:015
,0:005
+0:010
,0:005
+0:125
,0:005
Table 3: Required number of sheets and allowed variations in sheet length for the four stereo
super-layers of the COT.
the 4 stereo superlayers as measured on the test station at Harvard. All of the manufactured
sheets had lengths within 20 mils of nominal, which is well within tolerance given that the
measured deection of the COT endplates agreed with prediction.
One of our graduate students, Robyn Madrak, designed and built a eld sheet position
test xture. The purpose was to determine the average height of each eld sheet relative
to the endplate slot surface with an accuracy of 0.5 mils. This was done by measuring the
dierence in capacitances of the eld sheet and wire planes above and below the sheet. The
xture was used to test all 3000 eld sheets before they were installed in the COT.
Figure 3 shows the average height of the COT eld sheets as measured in Lab 6 at
Fermilab. The measurements were done in two congurations: with the eld sheets' stainless
steel wires above and beneath the gold mylar to which they are epoxied. Since the eld
sheet has both an intrinsic shape and a gravitational sag, its height is not the same in both
congurations.
Shown in Figure 4 are distributions of dierence in eld sheet position in going from the
\wires above" conguration to the \wires beneath" conguration. This is the amount, on
average, that the sheet moves with respect to the endplate slot surface (due to gravity) in
going from =0 to = 180. An interpolation may be performed to determine eld sheet
positions between the two extremes.
We also designed and built a wire tension measuring system (wiggler) to both test wire
continuity and measure the tension of every wire in the wireplane after installation in the
COT. We use a standard wiggling method, putting an AC current on the wire, which is
surrounded by a constant magnetic eld (produced by permanent magnets), and measure
the back emf as a function of driving frequency. We scan over a range of frequencies near

Section 2: Central Outer Tracker 9
35
30
30
25
25
20
20
15
10
15
10
5
5
0
-0.02 0 0.02
0
-0.02 0 0.02
SL1 (Corrected)
SL3 (Corrected)
50
80
40
70
60
30
50
40
20
30
10
20
10
0
-0.02 0 0.02
0
-0.02 0 0.02
SL5 (Corrected)
SL7 (Corrected)
Figure 2: Dierence between the desired eld sheet length and the measured lengths (corrected
for temperature and humidity variations) for the four stereo super-layers, in inches.
the expected resonant frequency, recording the amplitude at each point. The maximum
amplitude occurs at the resonant frequency. We nd the resonant frequency by tting
the amplitude vs. frequency distribution with a gaussian plus a at background, with the
mean being the resonant frequency. Figure 5 shows the output of the tension measurement
program for a single wire plane. The 25 plots arranged in a 55 array show the amplitude vs.
frequency distribution for all 25 wires of the wire plane. The measured resonant frequencies,
also converted to tensions using the linear density of the wire, are shown in the array atthe
left. Nominal tension on each wire is 150 g. Figure 6 shows the distribution of measured
tensions on all wires in each of the four innermost super-layers.
Since January, both students, Carter Hall and Robyn Madrak, and post-doc Kevin Burkett
have been running shifts, either to supervise chamber stringing, on the day and evening

10 Section 2: CDF Hardware
Figure 3: Field sheet heights are with respect to test xture 2-wireplane centerline. All
heights are averaged over area of sheet. Wires Above or Wires Beneath sheet refers to
orientation of stainless steel wires epoxied to Au-Mylar.
Figure 4: Variation in eld sheet position is movement of sheet due to gravity from =0to
= 180. (ie. in going from Wires Beneath) to Wires Above

Section 2: Central Outer Tracker 11
shifts, or to measure wire tensions and correct problems on the owl shift. They have been on
shift almost continuously, one on each shift. The stringing should be nished in early June.
The Harvard group will continue to be involved in the mechanical construction and checkout
of the COT. We will also be responsible for writing the online code which calculates and
monitors drift velocity and t 0 's for the COT. This is necessary to have working constants for
the trigger Level3 tracking code to run. This is part of a larger eort of ours to understand
the details of the COT chamber using a detailed Monte Carlo described in the next section.

12 Section 2: CDF Hardware
Figure 5: Front panel output of the wire tension measurement program.

Section 2: Central Outer Tracker 13
1200
1000
800
600
400
200
0
130 140 150 160 170
Wire Tension(g) - SL1
1800
1600
1400
1200
1000
800
600
400
200
0
130 140 150 160 170
Wire Tension(g) - SL3
1400
1200
1000
800
600
400
200
0
130 140 150 160 170
Wire Tension(g) - SL2
2000
1750
1500
1250
1000
750
500
250
0
130 140 150 160 170
Wire Tension(g) - SL4
Figure 6: Measured tensions in grams for all wires in super-layers 1-4. Wire planes with
tensions more than 5% from the nominal will be replaced.

14 Section 2: CDF Hardware
COT Detector Physics Simulations
When operating a big chamber like the COT it is desirable to have a detailed understanding
of all the detector physics processes, especially in the early phase of the experiment. In
order to get a good understanding of the performance and the operating parameters one
usually performs tests on small scale chamber prototypes before construction of the actual
detector. One can gain further insight into the chamber behavior by simulating the detector
physics processes and comparing them to the measurements. Three programs that allow
detailed detector physics simulations, GARFIELD [2], MAGBOLTZ [3] and HEED [4] have
recently been interfaced and improved considerably, such that now a full chain simulation of
all the detector physics processes from the passage of the particle to the output of the preamplier
is possible. A detailed comparison of drift chamber simulations and measurements
was done for the muon chambers of the ATLAS experiment [5] and the excellent agreement
allowed an ecient optimization of the detector parameters (Fig. 7).
130
120
110
100
90
80
70
60
50
40
0 2 4 6 8 10 12 14
Figure 7: Spatial resolution of the ATLAS muon drift chamber. The full circles show the
measurement, the open circles show the simulation; the agreement is very good.
Knowing that the simulation matches the measurements to about 10% it was possible

Section 2: Central Outer Tracker 15
to search for detector gases and electronics parameters with improved performance by just
running simulations which is quicker and more ecient than measuring large numbers of
dierent operating conditions.
Werner Riegler who did many of these simulations during his work on ATLAS joined the
CDF group last year and started to perform COT detector physics simulations together with
Melissa Wessels (1st year graduate student) and Tobias Jacobi (3rd year undergraduate).
Although the COT is already designed and in the process of being built it is still very
useful to perform these simulations since a profound understanding of the detector is the key
ingredient for a successful operation.
One example of the usefulness of such simulations is the time expansion chamber of the
L3 experiment at CERN where it was possible to improve the resolution signicantly by
using the results from a simulation in order to improve the calibration procedure [6].
In short: the goal of this work is a profound understanding of the detector performance
which will denitely provide useful for the operation of the COT.
Simulation Procedure
Three programs are used for the simulation: HEED simulates the passage of a fast particle
through the detector gas and calculates the charge deposit along the track. The GARFIELD
program tracks the individual electrons according the the electric and magnetic eld. The
gas transport properties like drift velocity, Lorentz angle and diusion are calculated by the
MAGBOLTZ program. Fig. 8 shows the equipotential lines of a drift cell and a single track
in the COT chamber.
Once an electron arrives at the wire the avalanche multiplication is simulated and the
wire signal is calculated by tracking the ions from the wire to the cathode sheets. Fig. 9
shows and example of an induced current signal on a single wire.
The signal is 'sent through the preamplier' by convoluting the induced current signal
with the preamp delta response and nally the drift time is found by applying a threshold
to the preamp output signal. By creating 2000 tracks at the same distance we nd the
space{drift{time relation and the spatial resolution for the given distance Fig. 10.

16 Section 2: CDF Hardware
Figure 8: The top gure shows the equipotential lines in a drift cell for the nominal voltage
settings. The bottom gure shows a single particle crossing the chamber. Note that each
individual electron is simulated.

Section 2: Central Outer Tracker 17
Figure 9: Induced current signal. The 'spikes' indicate the arrival of the individual electrons.

18 Section 2: CDF Hardware
120
300
100
250
80
200
60
150
40
100
20
50
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Figure 10: Simulation of the space{drift{time relation and the resolution as a function of the
distance from the wire (the distance is measured along the electron drift lines).
The full simulation is now running and we are ready to study the sensitivity of the
space{drift{time relation to pressure variations, temperature variations, threshold variations,
electronics noise, etc.
The COT will not only measure the particle tracks but will also be able to identify
particles by measuring their charge deposit (dE/dx). The HEED program is simulating
the velocity dependence of the charge deposit which allows us to also simulate the dE/dx
separation power for dierent particles and energies in detail. Fig. 11 shows a simulation of
the charge deposit spectrum of 10GeV Pion.
Future Plans
Our plan for the immediate future is to simulate spatial resolution, space-drift-time time
relations, dE/dx separation power and sensitivities to changing operating conditions. Since
we are able to simulate the expected drift chamber raw data very well we will also provide
an improved digitization scheme for the tracking Monte Carlo. In summer we will start to
compare these numbers to prototype measurements and in autumn we will nally be able to
compare the results to the real COT performance.

Section 2: Central Outer Tracker 19
All samples of 1000 tracks
8000
h1
Nent = 100000
Mean = 84.3991
RMS = 51.5945
7000
6000
5000
4000
3000
2000
1000
0
0 50 100 150 200 250 300 350 400 450 500
charge
Figure 11: Charge deposit spectrum for a 10GeV Pion.

20 Section 2: CDF Hardware
2.2.2 Data Acquisition for the Silicon Vertex Detector (SVX)
(Prof. Huth, Dr.
Maksimovic, Mr. Bailey & Ms. Spiropulu)
The Harvard group has made a long standing eort in SVX data acquisition, concentrated
on the Silicon Readout Controller (SRC). The most recent accomplishments of Huth,
Maksimovic, and Bailey, working closely with engineer Nathan Felt, are described below.
Preceding this was the ground-breaking work on the widely used Silicon Test Acquisition
and Readout (STAR) system and SVXIII chip by Spiropulu, Colin Gay (now at Yale),
Raimund Strohmer (now at MPI), and engineer John Oliver, which is described next.
Overview: Developments from 1993 through 1996
In 1992, a silicon vertex detector was added to CDF. It was used to detect secondary
vertices from heavy avor weak decays - an excellent tool for b-tags in top physics and for
B-physics. Due to radiation damage in 1993, CDF replaced this detector with SVX 0 which
uses AC-coupled detectors and a radiation-hard readout chip. Already in 1993 CDF started
working on the design of the silicon detector for Run II: the SVXII project.
The challenge of this project is the \dual ported" pipeline that stores the data during the
formation of the Level 1 trigger. The SVXII project uses the SVXIII chip which supports
simultaneous digitization and readout of data while additional analog data is entering the
pipeline. The SVXIII chip was jointly designed by Fermilab and LBL.
The Harvard group took responsibility for the design, prototyping, construction, and
support of one of the major components of the Data Acquisition stream, namely, the Silicon
Readout Controller (SRC). A schematic of the SVXII DAQ functionality isshown in Fig 12.
Long before the nal DAQ system was ready, the SVXII group needed to be able to read
out detectors with a chip as close as possible to the nal version (SVXII, SVXIIb). Studies
of signal-to-noise ratio before and after the silicon suered radiation damage were required,
as well as benchmark measurements of resolution, etc.
The initial team consisted of Huth (PI) John Oliver (engineer), Gay, Spiropulu and
Harlan Robins (undergraduate student). The prototype card that we designed and built was
called the Silicon Test Acquisition and Readout module (STAR).
By the summer of 1996 the Harvard group provided seven prototype STAR modules that
armed later test stand facilities all over the world (Lab D at Fermilab, Pisa, New Mexico,
Pittsburgh, KEK, to mention a few; they are still being used with great success. As the

Section 2: DAQ for the Silicon Vertex Detector 21
The SVXII DAQ
To Level 3
Trigger
CDF Clock
VME
Readout
Buffers
CMD
STAT
Silicon
Readout
Controller
CMD
STAT
Trigger
Supervisor
To Level 2
Trigger
DATA
4 Lines @ 132.5 MB/sec each
CMD
Fiber
Interface
Boards
STAT
CMD
DATA
10 Lines @ 53 MB/sec each
SVXII
Detector
Figure 12: Schematics of the SVX II data acquisition system.

22 Section 2: CDF Hardware
STAR was a critical component of the DAQ and since the group also carried online software
responsibilities for the DAQ path we inevitably became involved in the chip and detector
testing with this prototype DAQ architecture. We set up the rst laser and cosmic test
stand facility at Lab D at Fermilab, tested the DAQ stream, and the silicon wafers and
chips. Specically we performed measurements of the chip gain, the signal-to-noise ratio
for dierent vendor detectors using radiation sources and cosmics, the depletion voltage for
irradiated and unirradiated detectors, and we also investigated bulk inversion eects.
Post-doc Raimund Strohmer became heavily involved in the design and testing of the
SVXIII chip with the Fermilab probe station. This gave usthe opportunity to compare the
chip operation in the DAQ test stand and the probe station. We upgraded the STAR into
\super-STAR" to be able to handle the SVXIII chip and tested the rst SVXIII chips.
By the end of 1996 we also implemented the conceptual design and the most essential
logic of the nal Silicon Readout Controller (SRC). As the SVXIII chip control logic was
already implemented by the STAR, this became the heart of the nascent SRC, and the only
major change was the separation of the readout buers into a separate VME Readout Buer
(VRB) module (of which there are many in the production DAQ system). These modules
buer incoming level 1 accepted data while a level 2 decision is being made. Although the
average level 2 decision rate is faster than the the average level 1 accept rate, the VRBs can
buer up to 8 events in order to handle uctuations in the level 1 accept rate.
The Silicon Readout Controller (SRC)
The vertical-slice test of the prototype SVX DAQ system, consisting of prototype SRC,
prototype VRB, test FIB (TFIB), discrete port-card (DPC) and a radiation-soft version
of the SVXIII chip (version b) began in Spring 1997. Since this conguration included
neither trigger supervisor interface (TSI), nor CDF clock, those two functions were emulated
by the SRC. A Harvard-Yale team was led by Colin Gay. Engineer Nathan Felt was in
charge of hardware changes on the SRC, and Harvard student Greg Novak oversaw necessary
modications to all SVX online code. The prototype SVX DAQ system was successfully
operating by August 1997.
Since early fall of 1997, the whole SVX DAQ group has focused on the design changes of
the production boards. The resulting changes to the SRC can be summarized as follows:
Four FIB Fanouts vs. one: in the nal SVX DAQ, there will be four crates with
FIBs, each with a FIB Fanout module that receives commands from the SRC and

Section 2: DAQ for the Silicon Vertex Detector 23
passes them on to the FIBs its crate, and also collects the errors from the FIBs and
passes them on back to the SRC. On the SRC end, all logic that deals with four FIB
Fanouts is isolated into the SRC Transition Module, so, as far as the SRC is concerned,
there is only one FIB Fanout.
Error logging: the production SRC collects the error signals from VRB Fanouts and
FIB Fanouts, counts them and logs them.
Error handling: as the controller of the SVX DAQ system, the SRC is in charge of
how the system must respond to errors, both fatal and non-fatal, following the so-called
\Halt-Recover-Run" sequence. During the commissioning of the DAQ and the SVX II
detector, most errors will be fatal and we will investigate them individually. But once
the data taking commences, non-fatal errors will be logged, and fatal errors will be
handled in `auto-recover' mode. Here the interaction between the SRC and the Trigger
Supervisor is crucial, and it depends on whether the error is caused by the SVX system
or not, since in the former case it must take corrective action.
The necessary modications to the SRC schematics were mostly made by Felt and postdoc
Petar Maksimovic in the spring of 1998, along with the design of the SRC Transition
Module. The SRC and the SRC Transition Module printed circuit boards have been laid
out by Felt. The rst production SRC printed circuit boards were delivered in September
1998. One SRC was stued at Harvard and tested, block by block, by Felt, Maksimovic,
and graduate student Stephen Bailey, who began spending a signicant portion of his time
on the hardware side of the project. The majority of the SRC logic is implemented with
Xilinx Field Programmable Gate Arrays (FPGAs) which allows changes and new features
to be added even after the nal hardware has been assembled.
The communication between SRC and Trigger Supervisor (TS) was partially tested in
November. The rst production SRC was brought to Fermilab in November { the rst
production board in the SVX DAQ system { and the testing with the nal prototypes of
other SVX boards (FIB Fanout, FIB, VRB Fanout and VRB) began in earnest. After minor
tuning, in early December we were able to read out the SVXIII chip using the SVX DAQ
driven by the new SRC.
After that, other eight SRCs were submitted for assembly, while the SRC transition
modules were stued at Harvard. Several pairs of SRCs and their transition modules were
delivered to Fermilab in January 1999. The pilot (\pre-production") versions of VRBs and

24 Section 2: CDF Hardware
FIBs also became available at the same time, and we were able to check the communication
protocol between the SRC and the production versions of these boards. As this text is being
written, the pilot FIB Fanout (with which the SRC interacts directly) is not yet released,
however the preliminary tests showed that the SRC and the FIB Fanout can synchronize the
optical link and the SRC can pass commands to the FIB Fanout which then fans them out
to FIBs in its crate.
In early 1999, few other SRCs have been delivered to Fermilab, to control more sophisticated
tests of the other SVX DAQ boards, SVXIII chips, hybrids and port cards. The SRC
was rst employed in testing the pilot VRBs in terms of the return error messages that the
VRBs pass to the SRC (via VRB Fanout module), which counts them, logs them, and, if
necessary, acts upon them.
In addition, the VRBs had to pass the so-called \high-speed test", in which ve FIBs
are generating fake data, and send them via 50 optical links of production-type length to
ten VRBs. VRBs are operating in a mode where they check data consistency and report the
errors to the SRC, which counts them. The test is completely driven by the SRC, and the
role of software was reduced to telling the SRC to start and stop, and to periodically query
SRC's error counters. The test ran at the speed of 4 Gb/s (equivalent to lling up a typical
hard-drive in one and a half seconds!), and transferred about 10 16 bytes in just a few days.
CDF signed o on the VRB production order, and the SVX group plans on using this test
as a model for massive testing of large number of production VRBs.
The high-speed test required nalizing the baseline SRC rmware { mainly the logic
that handles the error condition in the SVX DAQ, which, in turn, necessitated nalizing
the VRB rmware as well. In addition, the specics of the high-speed test required other
small modications of the SRC rmware. This illustrates a crucial role that the SRC plays
in the testing and commissioning of the SVX DAQ system: its versatility allows for quickly
adapting the existing testing paradigms to new needs, as well as designing new ones, with
minimal or no modications to the rmware.
At the time of writing this report, our focus is on facilitating the testing of various aspect
of the operations of SVXIII chips, Intermediate Silicon Layer (ISL) hybrids and compact port
cards, e.g., performing gain scans and investigating the noise during digitization and readout
while the chip operates in the dead-timeless mode.

Section 2: DAQ for the Silicon Vertex Detector 25
Our Involvement in SVX Software
In the Spring of 1997, the rst version of the SVX online software was written at Harvard,
by Gay, Spiropulu and Novak. Although it began as the control software for the SRC, due
to its exibility and clarity it was soon accepted by the rest of the SVX DAQ group, and
then as the core of the CDF-wide protocol for controlling the boards in VME crates.
Motivated by the need for testing the SRC at Harvard { in absence of any other SVX
DAQ boards { the Harvard group began utilizing General System Test Modules (GSTMs),
developed by Fermilab's ESE group. Each GSTM is a generic board with several FIFOs and
ports for several types of daughter cards { each emulating a type of connection { that can be
attached to the GSTM. In this way a GSTM, adequately controlled by software, can emulate
any part of the SVX DAQ system. The low-level GSTM code has been written by Bailey and
Maksimovic. A high-level test-stand framework was proposed by Bailey and Maksimovic,
was implemented by other members of the SVX DAQ software team, and was extensively
used to test VRBs and FIBs using code written by Maksimovic that lets a GSTM emulate
a FIB or a VRB. The GSTMs are currently being employed in testing the Hit Finder board
of the Secondary Vertex Tracker system (SVT).
The SRC software was improved and is maintained mostly by Bailey, who also coded
various software tests appropriate for a stand-alone SRC test-stand (such is the one at
Harvard). Both Bailey and Maksimovic wrote tests that probe the functionality of the SRC
in the environment of the SVX DAQ (such is the one at Fermilab) { tests that involve all
elements of the system from the SVXIII chip up, and the ways they interact with the SRC.
Future Plans
At this point the basic functionality of the SRC has been tested and the majority of
the work is in the context of its integration with the rest of the system. This involves ne
tuning existing features, performing stress tests of its capabilities, and occasionally adding
new features to accommodate a specic test of the complete system. We are also writing
documentation for the testing and maintenance of the SRC to facilitate any trouble shooting
or repairs that may need to be done in future years when we are not working on the SRC
on a daily basis.
In the next year Maksimovic and Bailey will be applying their experience with the SVX-
DAQ system to aid in the construction and testing of the SVXII detector and will be involved

26 Section 2: CDF Hardware
in the installation and commissioning of the complete SVXII system.
2.2.3 Central Muon Extension (CMX)
(Prof. Schmitt & Dr. Dorigo)
Lepton identication is crucial for many of the most interesting physics topics to be
explored in CDF Run II. For example, muons are a basic ingredient for top quark studies,
B physics, the W mass measurement and certain searches for supersymmetric particles. To
make the best use of the data produced by the TeVatron, we need the widest possible ducial
coverage for both trigger level and oine muon identication. The CMX was designed to
increase the coverage of the Central MUon system (CMU) and its technical improvement,
the Central Muon uPgrade (CMP). A summary of the increases in acceptance provided by
the CMX is given in Table 4 for various physics processes. The gain from a well functioning
CMX is evident.
The CMX chambers extend the coverage of the central muon system from jj < 0:65
to jj < 1:0. Their construction is simple but robust: a single wire is strung in the center
of a rectangular aluminum extrusion, 6 1 inches in cross section and 72 inches in length,
lled with an argon-ethane mixture. This constitutes a drift chamber which can localize
the position of a muon track to within 3 mm. A constant electric eld is produced
by voltages applied to a series of copper cathode strips attached to the inner surfaces of
the extrusions. Signals propagating along the anode wire are amplied by simple circuits
mounted close to the end of the extrusion. The times of signals above threshold are digitized
in custom Amplier-Shaper-Discriminator (ASD) modules. To provide triggering capabilities
and precision timing information, the CMX chambers are sandwiched between two layers of
scintillation counters (the CSX system).
The drift chambers were built at Harvard and most of them were installed at the beginning
of Run I. Four arches, each made of twelve 15 wedges, were assembled and mounted on
separate stands (see Fig. 13) to provide partial coverage in the positive and negative
rapidity regions. Due to mechanical interference with other parts of the detector, however,
the top 30 and the bottom 90 on each side of the central detector were not installed.
The upgrade of the CMX system consists mainly in completing the coverage in . This
entails installation of two 15 sections (\wedges") on the top of the west side; these are called
the \keystone" wedges. The completion of the lower 90 of both the east and west sides is

Section 2: Central Muon Extension 27
a larger project. These sections are called the \miniskirt" and although the extrusions are
the same as the arches, the construction is dierent.
Process
Single muon acceptance
CMU & CMP CMU & CMP & CMX Relative improvement
WH ! ``` 0.46 0.71 56%
tt prod. 0.48 0.71 50%
WZ prod. 0.36 0.58 61%
Inclusive W prod. 0.30 0.52 71%
Inclusive J= 0.18 0.33 81%
Table 4: Improvement in the acceptance for single muons when the CMX is included with
the CMU and CMP, for various processes
Detailed Design
Each 15 CMX wedge is made up of 48 chambers arranged in stacks of eight layers; the
chambers are staggered layer by layer and form four logical hermetic layers, yielding four
position measurements for each crossing muon. The wedges have a fan-shaped structure,
and the CMX system, once assembled, forms two conical sections centered on the beam axis
{a somewhat unusual shape for a set of drift chambers. Each conical section is composed of
four mechanically independent parts: two arches, the keystone, and a miniskirt which covers
the lower part of the azimuth (see Fig. 14). Each arch covers 120 in azimuth, the keystone
at the apex covers 30 , and the miniskirt covers 85 (there are 2:5 gaps at the boundary
between the arches and the miniskirt). The construction of the east and west sides of CDF is
the same, except that there is no keystone on the east side, due to a mechanical interference
with the cryogenics.
The anode signals from the drift chambers are amplied locally. Radeka preamplier hybrids
are mounted on boards which service four tubes each. There is also a provision for test
pulsing the four channels on any given preamp board. The signals are brought on shielded
cables to a rack mounted on the CMX arch. Custom designed amplier-shaper-discriminator
(ASD) boards produce dierential ECL signals which are carried to multihit TDC's housed
on the rst oor of the experimental hall. These TDC's have been completely redesigned

28 Section 2: CDF Hardware
Figure 13: An engineering drawing of one of the four CMX arches.

Section 2: Central Muon Extension 29
Figure 14: The \miniskirt" drift chambers and scintillation counters comprising the lower
90 of the Central Muon Extension (CMX). There is one such set for each side of the CDF
detector.
for Run II, since the requirements on data acquisition rates are much more stringent than
in Run I.
The CSX scintillators are mounted on the interior and exterior surfaces of the wedges.
They are staggered with respect to the azimuth and each covers 3:75 ; in order to provide a
perfect t to the unusual design of the CMX system, these counters are built with a slightly
trapezoidal shape. There is one phototube on each scintillator; however, the orientation
on the interior and the exterior is opposite. This allows precise timing information to be
calculated from the sum of recorded times. (For the miniskirt there can be only one layer
of scintillator, due to space limitations. These scintillators will be instrumented with two
phototubes.)
Problems & Challenges
Our rst problem was the commissioning of the four CMX arches which contain the bulk
of the CMX chambers (Fig. 13). These were erected before Run Ib by individuals who are no
longer involved in the CMX. Our rst challenge was to understand how the system works,
and to repair whatever was not in good working order. Schmitt met this challenge after
arriving in 1998, assisted by undergraduate Kris Chaisanguanthum and graduate student
Hak-Ho Lee. Chaisanguanthum will be returning to Fermilab this summer, together with
undergraduate Caolionn O'Connell, to help assemble the miniskirt, as discussed below.

30 Section 2: CDF Hardware
Our main responsibility, aside from taking care of the four arches, is to complete the
azimuthal coverage of the CMX. The extent of the gaps in azimuth can be gleaned from
Fig. 15, which shows the (; ) coordinates of real muons in the Run I data. We describe
briey our completion of the keystone and our plans for the miniskirt.
φ
7
6
5
4
miniskirt
3
2
1
keystone
0
-1
CMX
CMU/CMP
CMX
-1.5 -1 -0.5 0 0.5 1 1.5
η µ
Figure 15: Coordinates (; ) of real muons. The large gaps in azimuthal coverage are labelled
according to the pieces we will use to ll them: the \miniskirt" for the lower 90 and the
\keystone" for the upper 30 (west side only).
Last Fall we assembled and tested the wedges comprising the keystone. This work was
carried out by Dorigo, Schmitt and an undergraduate Daniel Larson. The wedges were
damaged and required repair and minor refurbishing. Associated gas xtures, low and high
voltage connections and preampliers were mounted on the wedges, and the whole tested with
cosmic rays. Fermilab engineers and technicians installed a brace for the keystone wedges
on the ceiling of the collision hall. With their help we installed the complete keystone last
winter { it was the rst piece of apparatus to be installed for Run II. (Since then the four
arches have been placed in the collision hall, following a complete check-out last summer.)
The drift tubes for the miniskirt were fashioned at Harvard and assembled into

Section 2: Central Muon Extension 31
\wedgelets" which cover 5 each. These chambers will lie in a plane tilted 30 with respect
to the vertical. In all respects their performance should be the same as the rest of the
CMX system. In particular, the preampliers are the same as are the ASD's and TDC's.
By design the trigger will not distinguish between the arches and the miniskirt; they must
appear to be part of one homogeneous detector.
The miniskirt wedgelets must be supported on a stand. Unfortunately, the original plans
will not work, and so a complete redesign is in progress. The main constraints come from the
access required by other detector systems, including the CMP and the central calorimeter.
The new stand must allow access for quick repairs during the run, which makes its design
challenging. Moreover, allowance has to be made for thick cooling water pipes servicing the
silicon vertex detector.
This Summer one quadrant of the miniskirt will be assembled at Fermilab. After uncovering
the diculties of assembly, we will produce the remaining quadrants in order to be
ready for installation in 2000.
With the CMX complete, the increase in data potentially is quite large. Taking inclusive
W 's as an example, the CMUP+CMX sample is 57% larger than the CMUP sample. Plugging
the gaps in coverage amounts to an increase of 11% for central muons (jj < 1), and
leaves only 6.9% uncovered.
The CMX arches functioned well in the last run, as far as identifying muons is concerned.
There were major diculties with the CMX trigger, however. The basic problem was exposure
to soft particles scattered at large angles from the beam pipe and the forward detector
systems. Since the calorimetry did not shield the CMX from particles coming from the forward
direction (opposite to the interaction region), triggers from true muons were swamped
by fake triggers. Several measures were introduced to ght this problem. First, the beam
pipe was made thinner. Second, some activity in the hadron calorimeter indicative of a
through-going minimum-ionizing particle was required. Finally, the timing information from
the scintillators was fully exploited, to dierentiate between the time required for a muon to
reach the CMX from the interaction point and the time required for the fast particles from
the interaction point to hit the forward detectors and scatter debris back upinto the CMX.
Despite these eorts, the rate for the inclusive CMX muon trigger was till too high.
A fraction of the data, adjusted according to the instantaneous luminosity, was discarded
online, in order to not exceed the trigger bandwidth. This so-called \dynamical prescaling"
strongly reduced the collected data; we want to eliminate the need of dynamical prescaling

32 Section 2: CDF Hardware
80
CMX
CMX
60
gen.
40
fid.
20
acc.
0
-1.5 -1 -0.5 0 0.5 1 1.5
η µ
Figure 16: Comparison of three muon distributions from inclusive J= production. The
heavy curve indicates the generated distribution after a minimum P T cut. The lightly shaded
histogram shows the muons identied in the simulation, before any trigger requirements. The
darkly shaded histogram is the real data.
in Run II,oratleast reduce its impact as much as possible.
An idea of the loss of data is conveyed by Fig. 16. The heavy line (labeled \gen.") indicates
approximately the potential distribution of muons in from inclusive J= production,
after a minimum requirement ontheP T of the muon. The lightly shaded histogram (\d.")
shows the distribution of reconstructed muons in simulated data before any trigger requirement
is imposed. One sees a major loss of data due to the holes in azimuthal coverage,
as discussed above. A further loss of data occurs at the trigger level, however: the heavily
shaded histogram (\acc.") was made with real data. It is clear that the number of muons
from the CMX relative to the CMU/CMP region is far below what it could be. The rescue
of these muons and the physics potential they represent is a major goal of this
project.
Some measures have already been taken towards this end. Additional heavy steel has been

Section 2: Central Muon Extension 33
mounted to shield the CMX from the beam line and the material in the forward detectors.
This shielding is called the \snout" and it has the form of a thick ring tting just inside
the CMX. A smaller ring has also been installed, close to the beam pipe. Both the inner
and outer snout are welded on the huge pill-shaped plates which functioned as toroids in the
last run. Together they are expected to reduce the rate of fake triggers by a little less than
an order of magnitude. This estimate however is based on simulations whose accuracy is
not certain: fall-back solutions have to be developed in order to cope with any unexpected
sources of fake muon triggers.
There is another problem, discovered only recently, which concerns us. There is strong
evidence that the CSX scintillators are degrading with time much faster than expected. This
degradation is a combination of shorter attenuation length and lower brightness, and it is
observed as well in counters which were not near the beam, so it is not caused by radiation
from the beam. Although estimates indicate that the CSX will perform adequately for ve
more years, we are not satised that the problem is well understood. Since the main function
of the CSX was to assist in the trigger, we have to develop alternate trigger criteria which
do not rely on the CSX, in case the problem with the light output worsens. For example,
one could demand that a muon stub match a track in the central tracker in the second level
trigger. Studies are needed, however, to gauge the eciency and cleanliness of such a trigger,
and also its robustness. We also believe it is prudent to monitor the light output of a few
counters during the run, in order to spot any quick degradation which may occur: we would
not want to learn of a major eciency loss only after the data have been logged.
In order to design a trigger requiring a match of a muon stub with a central track, we
need to improve the model of multiple scattering and the magnetic eld. Careful studies of
stub-track matching from the Run I data and the Run II simulation are very important at
this stage; later, they will also be used for designing the oine analysis. Schmitt and Larson
have begun this work.
The CMX upgrade requires modications to the online and oine codes. CDF has
decided to rewrite all of its software in C ++ , so this eort is not trivial. The replacement of
other detector systems, such as the central tracker, implies major restructuring of the oine
software as well. This work was begun with in partnership with a graduate student from
Tufts, Dave Dagenhart, but the lion's share of the work remains to be done.

Section 2: Central Muon Extension 35
Work already performed
Commission the arches:
{ Fix bad preamp channels, ASD cards, scintillators
{ Add new hardware and electronics for the keystone and miniskirt
{ Perform needed modications for grounding and shielding
Assemble and commission the keystone:
{ Provide modications to solve mechanical interferences
{ Install electronics, gas ow, shielding, etc.
Work to be performed before the start of run II
Build and install the miniskirt:
{ Perform minor repairs of drift tubes
{ Design and build a mechanical stand
{ Install cables, electronics, gas ow, shielding, etc.
{ Install the complete systems in the experimental hall
Fix and prepare the readout electronics:
{ Do minor repairs needed by many of the ASD's and calibration cards
{ Prepare the ASD boards for the miniskirt (+ spares)
Software:
{ Rewrite decoding, pattern recognition and the simulation codes
{ Implement new online software for CMX data acquisition
{ Write new calibration & monitoring programs
{ Design trigger

36 Section 2: CDF
2.3 Run I Physics Analyses
The Fermilab TeVatron produces the most energetic particle collisions of any laboratory in
the world. As such it provides unique samples of top quarks and opportunities for searching
for physics beyond the Standard Model (SM). It also provides unmatched samples of
W bosons and B mesons, aording a wealth of studies of SM physics. The Harvard group
has investigated a wide range of topics with these data, most recently focusing on
events with jets and large missing transverse energy (6E T )
properties of the top event sample
the W mass
evidence for Z production via Z ! bb
We describe these analyses in the next section. They are based on all the data taken during
Run I (approximately 108 pb ,1 at p s =1:8 TeV).
Next year Run II will commence. The CDF Collaboration anticipates collecting
2000 pb ,1 at p s = 2:0 TeV. We have shifted our attention away from Run I physics in
preparation for physics at Run II. Naturally we do not know what will be found in those
data, but we have discussed where we would like to place our emphasis. We outline our
plans for Run II below.
To put our current activities in perspective, we provide a list of publications which
members of our group co-authored (page 98), and a list of completed Ph.D. theses (page 102).
It may also be instructive to review the list of recent major talks delivered by members of this
group (page 103) and our participation as referees (\godparents") in various CDF analyses
(page 100).

Section 2: Supersymmetry 37
2.3.1 Search for Supersymmetric Quarks and Gluons (~q, ~g)
(Prof. Huth & Ms. Spiropulu)
There are at least two seemingly fundamental energy scales in nature, the Electroweak
scale m EW 10 3 GeV and the Planck scale M Pl = G ,1=2
N 10 18 GeV, where gravity becomes
as strong as the gauge interactions. Supersymmetry provides a framework that explains the
smallness and radiative stability of the hierarchy m EW =M Pl 10 ,17 .
We are searching for supersymmetric quarks and gluons that would be strongly produced
in proton antiproton collisions (example diagrams for gluino productions are shown in
Fig. 17) and subsequently decay into nal states that are characterized by multiple jets and
the lightest neutralino (~ 0 ) which is the Lightest Supersymmetric Particle usually referred
to as LSP (example of gluino decays are shown in Fig. 18). The LSP interacts weakly with
matter and therefore escapes detection like a standard neutrino. The energy imbalance in
the event or missing transverse energy (6E T ) and the presence of multiple jets is a powerful
signature for the production of squarks and gluinos.
Table 5 summarizes the current experimental limits on the physical masses of squarks
and gluinos, the theoretically expected most natural mass and the mass reach at Run II.
Sparticle mass experimental limit most natural value TeVatron Run II reach
Squark 230(CDF,RUNIa),260(D0,RUNIb) 240 400 (GeV/c 2 )
Gluino 180(CDF RUNIa),190(D0,RUNIb) 240 400 (GeV/c 2 )
Table 5: Current experimental limits, most natural mass value, and Run II reach for squarks
and gluinos.

38 Section 2: CDF Physics Analysis
g
g ~g
q
g ~g
g
~g
q
~g
Figure 17: Gluino production diagrams
~g
q
~q q
~ 0 1
~g
q
~q q
~ 1
W
~ 0 1
~g
q
q 0
q
~q q
~ 0 2
Z 0
~ 0 1
q
q
Figure 18: Gluino decays
Data Selection
The data used for this search were recorded by CDF in 1993-5 and comprise 90 pb ,1
(Run Ib). A multi-level online trigger selected 2.6M events with 6E T > 35 GeV. On average
there were 3.5 interactions per crossing, due to the high instantaneous luminosity. It is
crucial that we understand the composition of the sample and identify the sources of missing

Section 2: Supersymmetry 39
transverse energy in the data. The main sources that can mimic the 6E T + jets signal, and
therefore backgrounds to the search, are:
Events with Main Ring accelator induced 6E T
malfunctions (source of fake 6E T )
detector noise and other instrumental
cosmic ray muon Bremsstrahlung (source of fake 6E T )
QCD events with 6E T arising from detector mismeasurements unistrumented regions
(cracks), jet energy resolution (source of fake 6E T )
Z QCD associated production where the Z decays to (source of real 6E T )
W QCD associated production where the W decays to (source of real 6E T )
tt production where the top decays to a W and a b quark and the W decays to lepton
and neutrino, (source of real 6E T )
We perform an aggressivemulti-stage clean-up of the trigger sample that rejects eciently
cosmic background, instrumental background and jet mismeasurement backgrounds.
At the rst stage it is important to improve the measurement of the 6E T in events
with multiple vertices. This is implemented by identifying the main event vertex as the one
associated with the highest momentum sum and reprocessing the data. At this stage the
relative time stamp of the energy on the hadronic calorimeter and the beam crossing is used
to reject Main Ring accelerator induced 6E T triggers and cosmic background.
At the second stage the quality of the jets present in the event is tested by using the
ratio of the electromagnetic to total energy in the event and the fraction of total transverse
energy in charged particles (averaged over the tracks matching central clusters in the event).
Residual cosmic ray background and overlap events with Main Ring hadronic splashes as
well as other detector malfunctions are being eliminated at this stage.
The eect of the clean up is shown in Fig. 19. The three distributions overlayed are
the 6E T distribution of the trigger sample (largest tails), the sample derived after the rst
cleanup selection is applied (6E T tail up to 300 GeV) and the corresponding one after the
second clean up selection is applied.
A signicant source of fake 6E T is due to jets landing in non-ducial regions of the detector
(cracks) and causing energy imbalance in an event that would be otherwise a balanced QCD

40 Section 2: CDF Physics Analysis
Figure 19: 6E T ditributions (I) online trigger sample (II) after rst stage cleanup requirements
applied (III) after second stage cleanup requirements applied.

Section 2: Supersymmetry 41
multijet event. We developed a `tomographic' cleanup algorithm to reject the events with
the second most energetic jet pointing to a crack and being collinear with the missing energy
vector.
We refer to this procedure as \jet verication" and it is a a crucial element for
improving the reach of this analysis.
In the diagram of Fig. 20 a side view of quarter of the detector is drawn and the cracks
where the jets might escape detection are shown. One expects in the case of jets being lost
in the cracks the events to be distributed in the vs zvertex plane as shown in the bottom
diagram of Fig. 20.
Indeed in Fig. 21 we see this behavior in the data where the second jet falls in a detector
boundary and the 6E T is collinear with the second jet. We reject the events that fall in the
high density stripes on both the 2nd jet detector -event z vertex plane and the 6 E T
- 2nd jet
(in radians) plane.
The following requirements are designed to have good W/Z/top background rejection
eciency, they make use of the kinematic and topological characteristics of the SUSY signal
and eliminate residual QCD mismeasurements:
at least 3 jets
6E T 60 GeV
2nd jet
H T = ET
3rd jet
+ ET + 6E T : :200 GeV .
None of the two leading jets should be purely electromagnetic
No azimuthal correlation between the direction of the rst two jets and the 6E T .
After this selection the signal eciency for a high squark gluino mass point in the SUSY
parameter space is 15%. This signies an improvement over the Run Ia CDF seach (eciency
in the range of 1-5%) and over the Run Ib D0 search (in the range 1-10%).
W, Z Background Normalization
In order to get a precise estimate of the W/Z QCD associated background with a
neglidgable systematic dependance on the renormalization and factorization scale we normalize
the Monte Carlo prediction for Z ! + 3 jets and W ! + 2 jets rates
using the data rates of Z ! e + e , + 2 jets.

42 Section 2: CDF Physics Analysis
Figure 20: (upper) A quarter side view of the CDF detector. c, w, p stand for central, wall
and plug calorimeters; bl stands for the beamline and is the z direction (the direction of the
protons, antiprotons). (lower)Expected distribution of events in the vs z vertex plane when
a jet is falling in uninstrumented regions of the detector.

Section 2: Supersymmetry 43
Figure 21: detector - event z vertex plane for the second jet and 6 E T
- 2nd jet plane.
We use the Z resonance data because there is little background under the Z peak in
the CDF data. The shape of the kinematic distributions (P T of the boson, jet E T , jet
, 6E T , as well as other event topology related variables) in the Monte Carlo are in good
agreement with the shapes observed in the data. To use the same normalization scheme in
the W plus jets processes (i.e. using the Z data) we examine the ratio of the
in the data. Figure
W !e+2 jets
Z!ee+2 jets
22 shows the raw ratio in the data and the ratio after applying the
Acceptance(A) efficiency() for the selection of the Zs and the Ws.
Also we use lepton universality, namely the ratio of
W !e+2 jets
W !+2 jets
to validate the normalization
scheme in the W ! + 2 jets QCD predictions. Fig. 23 shows this ratio in the
raw data and after the Acceptance(A) efficiency() applied.

44 Section 2: CDF Physics Analysis
Figure 22: 2: Raw ratio N We
N Ze
in the data. 4: RWZ e = N We
N Ze
ZeA Ze
We A We
. The hatched region
shows the CDF1A measurement and its statistical uncertainty.

Section 2: Supersymmetry 45
Figure 23: 2: Raw ratio N We
N W
in the data. 4:
standard model prediction.
N We
N W
WA W
We A We
.The line at 1 is the ge
g

46 Section 2: CDF Physics Analysis
Indirect Lepton Veto
Since all the Standard Model backgrounds contain in the nal state along with 6E T and
jets also a lepton we dene an isolated track criterion to select the remaining standard model
processes in the data. The composition of the complementary sample of events that do not
contain such an isolated charged track is expected to be QCD events with large 6E T arising
from pure jet calorimeter resolution. Any excess of events in this sample will be the signal
candidates.
We are modelling the QCD background using large monte carlo statistics samples of
inclusive 3 jet QCD events and by varying the jet resolution functions in order to get the
shape variation of the 6E T tails. This is a critical part into arriving to the result of the search
for the supersymmetric signal. Completion of this part of the analysis and optimization of
the requirements for identication of signal candidates will allow us to compare the data with
the total background predictions. The QCD prediction of the low 6E T spectrum for events
with at least three jets compared with the data is shown in gure 24. The comparison of
the sample of events that do contain an isolated track with Standard Model predictions for
the backdrounds mentioned above (where we expect very low or none QCD contribution) is
shown in g 25.
We still need to study and estimate the systematic uncertainties for the Standard Model
predictions. We expect a result of this search by the Fall of 1999.

Section 2: Supersymmetry 47
Figure 24: 6E T spectrum from QCD prediction for events with 3 jets overlayed with the data.

48 Section 2: CDF Physics Analysis
Figure 25: Standard Model prediction (from top, W,Z associated production, diboson production)(histogram)
for events with 1 isolated track overlayed with the data (points) passing the
same rquirements.

Section 2: Top Cross Section 49
2.3.2 The Top Quark
(Prof. Franklin, Dr. Ptohos, with the Frascati group on CDF)
The existence of the top quark was established by the CDF and D0 collaborations and
a rst measurement of the top pair production cross section and the top quark mass was
reported in References [7, 8, 9, 10]. Now it is vitally important to check for the existence
of new physics associated with top production and/or decay. For this it is essential to reevaluate
backgrounds and verify the analysis tools that were developed for the discovery of
the top quark. This re-evaluation is prompted by the higher than theoretically expected
cross section (as measured with W + 3 jets sample) and also by a small excess of events
in the W + 2 jet multiplicity bin.
In this spirit, we engaged in an extensive revision of the tt analysis in the lepton+jet
channel with heavy avor tagging. This decay channel is the dominant signature upon
which the top discovery is based. Our eorts provided the basis for the Higgs search in the
W +2jet sample (discussed below) and have spawned wide ranging investigations of top
sample which are still underway.
We started the revision of the tt analysis with a more careful isolation of the W +n jet
data sample by identifying and removing Z and dilepton candidate events which otherwise
would contaminate the W sample. In an eort to avoid a miscalculation of the missing transverse
energy and jet multiplicities caused by confusion in the choice of event vertex due to
overlapping interactions, we developed a new method for determining the event vertex based
on the location of the primary lepton vertex. This new method recovers some additional
tags which were otherwise lost due to wrong track-jet association requirement.
In order to increase our sensitivity to tt events and our understanding of the various
background contributions we used three dierent algorithms to tag heavy avor jets. The
rst of these is SECVTX which identies heavy avor jets based on the presence of a displaced
vertex inside a jet. This algorithm was used by CDF for the discovery of the top quark and
is very ecient mainly for tagging b-quark jets.
The second technique is based on the identication of leptons from the semileptonic decay
of a b or c-quark jets. This algorithm, known as SLT tagging, was developed in previous
years by members of the Harvard group (D. Kestenbaum and M. Franklin). For this analysis,
the SLT algorithm was slightly revised with respect to the standard one used at CDF. First,
we required the SLT tagged lepton to be within DR 0:4 from the axis of a jet with E T 15

50 Section 2: CDF Physics Analysis
GeV. This requirement is 95% ecient for tt events while removing most of the soft lepton
tags arising from Drell-Yan, Z or upsilon production which are quite isolated. Secondly, we
extended the Method II background calculation to the SLT tagged sample. In order to do
this correctly, we subtracted from the raw fake tag rate the fraction ( 10%) associated with
real heavy avor jets.
The third technique is called the \jet probability" tag. This algorithm uses the impact
parameter of a track contained in a jet to determine the probability the track originates from
the primary vertex, given the SVX detector resolution. The combination of the probabilities
of all tracks in a jet gives an overall probability for the jet, i.e., the jet probability or \JPB."
For heavy avor jets, this probability is expected to be small.
Our requirement on JPB is loose in the sense that the eciency for b-jets is about the
same as SECVTX, while about twice the number of c-jets is accepted. Since the overlap
of JPB and SECVTX is large, this new algorithm does not bring much new information in
terms of b-quark tagging. However, the loose JPB tags are more sensitive than SECVTX to
backgrounds from mistags and c-quark jets, a fact which we have exploited to study these
important backgrounds. From these studies we uncovered and corrected some inconsistencies
and mistakes in the standard Method II background calculations developed for SECVTX
tags. We also showed that the eciencies for SECVTX were underestimated by 25% relative
by studies of the low-P T inclusive electron sample. In contrast, the resolution functions
required by JPB are derived separately for data and Monte Carlo, leading to a relatively
reliable performance.
The problems with the SECVTX eciency led us to re-evaluate the rate of gluon splitting
to b b and cc pairs, important for estimating the amount of W + b b and W + cc background.
Before correcting SECVTX b-tagging eciency, we had found inconsistent results
from SECVTX and JPB. Applying the correction, however, the two algorithms gave identical
results. This lends credence to the SECVTX eciency correction we derived.
We developed a new technique for explaining and determining the amount of SECVTX
and JPB mistags using the characteristics of JPB. Our simple model successfully predicts
the rate and kinematical distributions of instrumental backgrounds with better than 10%
accuracy is superior to the method developed in the old analysis. It also allows for an
improved understanding of the heavy avor tagging and the mechanisms contributing to the
negative tagging rate.
Based on the new techniques and the extended background studies described above,

Section 2: Top Cross Section 51
we measured the tt cross section in the W + 3 jet sample for each of the three tagging
techniques. We obtained the following results:
t t = 5.08 1.54 pb using SECVTX tags.
t t = 8.02 2.16 pb using JPB tags.
t t = 9.18 4.26 pb using SLT tags.
These results have now been blessed as the ocial CDF top cross-sections, and a paper will
be submitted this summer.
All measured cross sections are in agreement with the theoretical value t t =4:7 5:5 pb
for a top quark mass of M T = 175 GeV [11, 12, 13]. The tt cross section measured using
SECVTX tags and the cross section measured by D0, using strict kinematical selection
criteria tuned on a top mass of 175 GeV are in good agreement with the theory. On the
other hand, values measured with JPB or SLT (including the D0 value) are higher. The errors
associated to each cross section are large, but are also highly correlated (e.g., uncertainties on
the luminosity, acceptance, lepton identication eciency). In comparing the SECVTX and
JPB results, the only error not in common is the uncertainty in the tagging eciency of each
algorithm, which is of the order of 10%. These two cross sections dier by 2:5 0:8 pb. In
comparing the SECVTX and SLT results, the errors not in common are statistics and again
the systematic uncertainty on the tagging eciency. The observed discrepancy between the
two cross sections is 3:5 1:6 pb. Compared correctly, these dierences are statistically
signicant. However, when we measured the b and c-quark tagging eciencies we found that
the ratio of c-quark eciency to b-quark eciency for the SLT and JPB taggers is a factor
two higher than for SECVTX.
The standard procedure for calculating the tt cross section assumes that the excess of
tags in the data with respect to the predicted background is all due to b-quarks and tt
production. If part of the excess was due to c-quarks, then it would happen exactly what it
is seen in the data.
It is interesting to study how the excess of events with JPB and SLT tags is distributed
with respect to events tagged by SECVTX. For this study, we divided the W sample in
events with or without SECVTX tags. We also assumed that the composition of these two
samples is as determined by the measurement of the tt cross section with SECVTX, i.e., we
assumed that with a jet tagged by SECVTX are almost pure b while events without such a
tag contain:

52 Section 2: CDF Physics Analysis
60
Events with SECVTX tags
Events without SECVTX tags
50
JPB tags
data
100
JPB tags
data
Number of tagged events
40
30
20
Top
QCD
Number of tagged events
80
60
40
Top
QCD
10
20
0
1 2 3 ≥4
Number of jets
0
1 2 3 ≥4
Number of jets
Figure 26: Comparison of the observed and predicted rates of JPB tags in events with and
without SECVTX tags. The predictions are based on the W sample composition determined
by the measurement of the tt cross section with SECVTX.
Direct production of W +jets without heavy avor.
Most of the events due to W + c b and Wc production, since SECVTX is less ecient
for tagging c-quark jets.
Events due to Wb b production when the b-jets are not taggable (SECVTX is more
ecient for tagging b-jets than JPB and SLT).
Rates of observed and expected JPB tags in the two samples are shown in Figure 26.
In the W + 2 jet events tagged by SECVTX, the observed number of JPB tags agree
with the expectations. The excess is 6:027:67 events. In the remaining W + 2 jet events,
there is an excess of JPB tags of 20:26:1 events. This excess is as large as the total number
of tt events tagged by SECVTX (21.1 events). It could be explained by a miscalculation of
the Wcc and Wc contributions or by a W + c-jets production process unaccounted by the
Standard Model. On one hand, the good agreement between the observed and predicted
rates of JPB tags in W +1jet events (which are dominated by Wc and Wcc production)

Section 2: W Mass 53
Number of tagged events
12
10
8
6
4
Events with SECVTX tags
SLT tags
data
Top
QCD
2
0
1 2 3 ≥4
Number of jets
Figure 27: Comparison of the observed and predicted rates of SLT tags in events with
SECVTX tags. The predictions are based on the W sample composition determined by the
measurement of the tt cross section with SECVTX.
seems to exclude a mistake in the predictions. On the other hand, since the tagging eciency
of JPB for c-jets is a factor of two smaller than the tagging eciency of SECVTX for b-jets,
it implies that the new W + c-jets production mechanism will have a cross section a factor
two larger than tt production.
For the SLT, it is useful to compare observed tags to expectations only in the sample
tagged by SECVTX since the sample without SECVTX tags has too much background. The
rates of observed and predicted SLT tags are shown in Fig. 27. In the W + 2 jet sample
tagged by SECVTX, there is an excess of 7:33:3events to be compared with an expectation
of 5.3 top events. So, in the SLT case, there is no sign of a discrepancy, within the large
statistical uncertainty. Still we are studying the kinematic features of these events and nd
some surprising features which cannot easily be explained by Standard Model processes.
More work is required before we fully unravel the mysteries behind these fascinating
anomalies. An article for Physical Review reporting the cross section measurements given
above is planned. These cross-sections have been recently blessed by the CDF Collaboration.

54 Section 2: CDF Physics Analysis
2.3.3 The W Mass Measurement
(Prof. Franklin & Dr. Gordon)
The W mass is measured at CDF using both electron and muon decay channels. The
Harvard group worked on the electron decay mode. W ! e decays are characterized by
a high E T electromagnetic cluster and large 6E T , where the EM cluster has a high P T track
pointing at it. Here E T refers to the calorimeter measurement and P T to the measurement
from the central tracking chamber (CTC). The W mass is extracted from a t to the transverse
mass distribution. Using the data (80 pb ,1 ) from Run IB, a statistical error of 70 MeV
is obtained, which is half the error of the previous measurement.
An equally large source of uncertainty arises from the determination of calorimeter energy
scale. Z decays can be used to set the energy scale with an uncertainty of 0:1%. We can
also tie the calorimeter scale to the CTC scale with the peak of the E/p distribution, where E
is the calorimeter measurement, and p is the CTC measurement of the electron. Attothe
E/p distribution is shown in Figure 28. Bremsstrahlung causes a shift in the peak and also
creates a large high-end tail. The statistical error associated on the peak position is 0:04%,
and there is an additional uncertainty from the amount of material inducing Bremsstrahlung
of 0:04%. The corresponding error on M W is also 0:04%.
Unfortunately, the energy scale as determined from the E/p distribution and from the
Z mass dier by 0:45%, and this is a 4 deviation. Simply stated, if we set the energy
scale using the E/p distribution, then we measure avalue for the Z mass which is 410 MeV
too low. A great deal of eort has been expended looking for the solution to this problem.
Among other things, we have checked the following:
The E/p distribution from Z decays agrees with the distribution from W decays, which
indicates that the problem is not a simple non-linearity in the energy scale between
W and Z energy scales.
Possible non-linearities were further constrained by obtaining the E/p distribution
from decays ! e + e , . Extreme non-linearities would be required to explain the E/p
anomaly, and are completely ruled out from this distribution.
We have applied our Monte Carlo to analyze the Run Ia data and have reproduced the
Run Ia results well, including both the Z mass and E/p distribution. This indicates
that we have not introduced a bug by various changes in the simulation. Whatever

Section 2: W Mass 55
problem we are seeing may also have been present in Run Ia as the Z mass obtained
from these data is consistent with both the CERN result of 91:187 GeV as well as a
number 410 MeV lower.
A better momentum measurement is obtained by including a beam constraint in the
track it. This constraint tends to bias electrons which have radiated towards higher
P T , and if we are not simulating the beam constraint correctly, we may fail to correct
for this bias. From the impact parameter resolution, the width of the E/p distribution,
and correlation between E/p and impact parameter, we can see that the Monte Carlo
covariance matrix does not perfectly describe the data. We have tried perturbing
the covariance matrix, including tting to the data directly, but we have seen only
negligible changes in the E/p peak position.
Radiative decays W ! e modify the E/p distribution. If they are not simulated
correctly, asystematic error could result. We nd that internal Bremsstrahlung shifts
the E/p peak by :25%. If our generator is wrong by 100%, then this might
account for some of the eect we are seeing. Our default generator is PHOTOS,
but we have also tried using a Berends and Kleiss calculation [14], as well as a more
recent calculation by Baur, Keller, and Wackeroth [15]. We have also implemented
an algorithm by Laporta and Odorico [16], and all these calculations give the same
results. All these calculations, of course, are based on the same physics, nonetheless
the similarity of the results makes it unlikely that there is a bug in the generator code,
or our implementation of it.
Recently CDF has re-calculated the CTC calibration and alignment. While this improves
the P T resolution by 10%, the E/p peak position does not change.
The ALEPH and KTeV Collaborations have observed systematic dierences in tracking
electrons as compared to muons and pions. This is thought to come from the eects of
keV level photons emitted by the electron as it passes through the gas. The sensitivity
to these photons depends greatly on tracking algorithms. We modeled these eects
in detail and showed that they would be important only if they were ten or twenty
times larger. We also compared exhaustively the properties of the electron and muon
tracks from W and Z decays and found no important dierence. Finally, we compared
the masses for J= and obtained from electron tracks and, taking into account the
relatively large radiative corrections for electrons, observed good agreement with the

56 Section 2: CDF Physics Analysis
masses obtained with muon tracks. We concluded that for CDF electron and muon
tracks are essentially the same.
We have also checked a number of interesting possibilities, all of which turn out to
be insignicant. One is the Landau-Pomeranchuk-Migdal eect, which can suppress
soft Bremsstrahlung. SLAC has measured this eect for 25 GeV electrons, and the
amount of suppression shown by that experiment does not signicantly change the
E/p shape. We have also considered the possibility that the 400 of aligned silicon
crystals in the SVX may cause signicant energy loss for electrons traveling along an
axis of symmetry. The E/p distribution for electrons which do not pass through the
SVX looks the same as those which do, and we conclude that this is not a signicant
eect. The electron is being accelerated in a circle by the magnetic eld, and we are not
simulating the resulting synchrotron radiation. This is predicted to be only a few MeV
however, and can be safely neglected.
We will use the Z mass to set the energy scale, as this avoids nearly all systematic errors
related to tracking. Nevertheless, the contradiction with E/p remains and is interesting in
itself.
We have also completed a model of the neutrino measurement. The missing E T measurement
is dominated by the electron E T , but it also contains signicant contributions from
energy unassociated with the event, and also from the low energy particles which balance the
W transverse momentum. We write U ~ for the vector sum of all the transverse energy in the
event, excluding the electron energy E T . Instead of trying to model ~U from rst principles,
we produce an empirical model which is t from Z data.
The model treats U 1 and U 2 as independent, Gaussian random variables, where U 1 is ~U
projected parallel to the boson, and U 2 perpendicular. The mean of U 2 is assumed to be
zero, while the mean of U 1 varies with the boson P T . The variation of the mean of U 1 with
boson P T is t from the Z data. The widths of both variables are determined from the total
energy in the event, and are also allowed to vary slightly with the boson P T . Figure 29 shows
the U 1 and U 2 distributions of the data. For the gure, we have subtracted the predicted
value for the mean of U 1 and divided by our predicted resolutions. The evidence that our
model is reasonable is that both distributions correspond well to Gaussians centered on zero
with unit widths.
The P T distribution of Z's in the data is only known within the measurement resolution,

Section 2: W Mass 57
and we correct for the eect that this has on our model ts before we apply the model to
the W Monte Carlo. Since the Z data sample is signicantly smaller than the W sample, we
do not necessarily expect a perfect t to the W data. Nevertheless, we are able to perturb
the model to describe both the W data and the Z data simultaneously. The uncertainty
related to the modeling is 15 MeV on the W mass. This includes the uncertainty on the
P T distribution for the W's.
The backgrounds have also been estimated. The largest background is W ! ! e,
and there is also a background contribution from QCD events where one jet is apparently
electromagnetic, and the other is lost. Both the background and the QCD background
occur at low M T { only 0:8% and 0:5% of the events in the high M T tting region are from
these backgrounds, respectively. There is also a 0:1% background from Z events, where
one of the electrons passes through a calorimeter crack. All these backgrounds are included
in the ts, and they are small enough to have negligible eects on the results.
The mass of the Z bosons both in the electron and muon channels are shown in Figure 30.
The analysis is complete in all respects, and Gordon successfully defended his thesis in
November 1998. The electron and muon results were presented at conferences this winter
and will be submitted to Physical Review this summer. The nal uncertainties are listed in
Table 6. The nal results for the W mass are in the electron channel, Mw = 80.473 0.113
GeV, in the muon channel, Mw = 80.465 0.143, and the combined measurement, muons
plus electrons, Mw = 80.470 0.089.

58 Section 2: CDF Physics Analysis
Figure 28: Best t E/p distribution for W events. Top left and right: Best t E/p distribution
for Monte Carlo (histogram) with data overlayed (crosses), on a linear and log scale. Bottom:
the residuals of the top plot, data minus Monte Carlo. The errors on the bottom points
are the statistical errors associated with the data. Summing the squares over the points
divided by their errors gives 2 =dof = 1:15. The tracking resolution for the Monte Carlo
has (1=P T )=:00085 GeV ,1 . For 8% of the events, however, we use a second resolution of
(1=P T ) = :0026 GeV ,1 . This second resolution is needed to account for the low-end E/p
tail.

Section 2: W Mass 59
Figure 29: The distribution of (U 1 ,)= 1 (top) and U 2 = 2 (bottom) for all the Z data, where
the model parameters are used tocalculate , 1 , and 2 . Gaussian ts to the histograms are
overlayed, and the means and widths of the ts are printed on the plots.

60 Section 2: CDF Physics Analysis
# Events
2000
1500
1000
500
CDF(1B) Preliminary
W→eν
χ 2 /df = 82.6/70 (50 < M T
< 120)
χ 2 /df = 32.4/35 (65 < M T
< 100)
Mw = 80.473 +/- 0.065 (stat) GeV
Backgrounds
KS(prob) = 16%
Fit region
0
50 60 70 80 90 100 110 120
Transverse Mass (GeV)
Figure 30: . The transverse mass of the W boson in the electron neutrino channel. The
histogram is a t to the region indicated.

Section 2: W Mass 61
250
200
CDF(1B) Preliminary
Z→ee χ 2 /df=1.3
κ %
2.25
2
1.75
2σ
1σ
150
1.5
100
1.25
50
1
0
70 80 90 100 110
CDF(1B) Preliminary
250
Z→µµ χ 2 /df=0.89
200
150
100
50
σ(1/p T
)x10 -3 GeV -1
1.05
1
0.95
0.9
0.85
0.998 1 1.002
Mz/Mz(LEP)
2σ
1σ
0
80 90 100
0.8
0.998 1 1.002
Mz/Mz(LEP)
Figure 31: Shown on the left is the Z mass in the muon and electron channels used for setting
the energy scale of the calorimeter. On the right are plots of the resolution of the calorimeter
or tracking chamber, versus the ratio of the tted Z mass to the LEP measured Z mass.

62 Section 2: CDF Physics Analysis
Table 6:
source of error W ! e W !
statistics 65 100
energy scale M Z E=p M Z M
75 80 85 20
P W T & recoil model 40 40
parton distribution functions 15 15
higher order QED corrections 20 10
energy resolution 25 20
trigger & selection bias { 15+10
backgrounds 5 25
total systematic (w/o scale) 54 57
total uncertainty 113 117 143 117
Uncertainties in the W mass measurement, in MeV. \Energy" refers to the
calorimeter measurement for electrons, and to the track momentum measurement for muons.
In the electron channel the scale is being set by the Z mass and so the total uncertainty is
113 MeV

Section 2: Z Decays to bb 63
2.3.4 Study of the decay Z ! bb
(Dr. Dorigo)
While decays of Z bosons to b-quark pairs have been studied for some years at LEP and
SLC, they have never been observed in pp collisions. The extraction of a signal in Run I data
is therefore interesting. The knowledge gained will prove invaluable for designing advanced
dedicated triggers for Run II. These events would help calibrate the absolute energy scale
for b-quark jets, substantially reducing one of the critical sources of systematic uncertainty
in the top quark mass measurement.
CDF PRELIMINARY
Events per 10 GeV/c 2
120
Selected Sample
100
— Unbinned Likelihood Fit
80
– – Background
60
… Z → bb Signal
40
20
0
0 20 40 60 80 100 120 140 160 180 200
Dijet Invariant Mass (GeV/c 2 )
Events per 10 GeV/c 2
5000
4000
3000
2000
1000
Background Sample
— Unbinned Likelihood Fit
0
0 20 40 60 80 100 120 140 160 180 200
Dijet Invariant Mass (GeV/c 2 )
Figure 32: Top: the Z peak in the signal sample; bottom: a signal-depleted sample is used to
extract the background shape.
Dorigo extracted a signal for Z ! b b signal using kinematic tools and b-quark tagging for
his Ph.D. thesis with Padova University (see Fig. 32). Starting from a dataset of about ve

64 Section 2: CDF Physics Analysis
million events enriched in b-quark decays, collected using an inclusive single-muon trigger,
he devised avery tight selection, which increased the signal over noise ratio by three orders
of magnitude. He isolated a signal of 91 30 events.
Dorigo is continuing the work on this signal, rening the tools needed and increasing
the acceptance of the selection. He has in view of the utility of a well identied Z peak
as a unique calibration tool. The Z ! b b peak also provides a perfect testing ground for
algorithms designed to improve the dijet mass resolution, which is one of the critical points
for the discovery of the Higgs boson in Run II (see Sec. 2.4.6).

Section 2: Run II Discovery Physics 65
2.4 Run II and Beyond
The prospect of a much larger and improved data set raises hopes for the discovery of physics
beyond the Standard Model. The Harvard group has set its sights on discovery physics and
on measurements of CP violation in the b system. We describe our plans and achievements
in these two areas below.
2.4.1 Discovery Physics
There are two approaches to searching for New Physics which are sometimes called \datadriven"
and \theory-driven." They are somewhat opposed philosophically, and each has it
advantages and disadvantages.
The idea behind data-driven searches is that a well-dened event sample thought to be
explained by known processes should be studied thoroughly with an eye open for important
discrepancies between observation and expectation. For example, a valid measurement of
the cross section for tt production, in principle a well-understood SM process, could turn
out higher than expected. One would conclude that the selected event sample would contain
events from new physics processes. If the measurement were below expectation, then it could
indicate unusual top decays to states not satisfying the given selection criteria. If pursued
seriously and with alacrity, almost any measurement of SM processes could open a window
to an unexpected discovery.
The weakness of data-driven searches is the danger that uctuations are innocently massaged
into signals. This weakness is avoided in the theory-driven approach, in which a signal
is proposed and modeled, allowing a priori selection criteria to be designed using simulations
before the data are queried. In principle the criteria are unbiased with respect to features of
the data, so when applied to the real data, a signicant excess of events is either observed, or
not. In practice the diculty of modeling some of the backgrounds often precludes nalizing
the selection criteria before the data are looked at. More importantly, the criteria designed
for a signal suggested by a popular theory may fail to ferret out a real signal quite dierent
from what that theory predicts. In other words, there is a danger of looking very seriously
and systematically for the wrong signals.
We do not wish to adopt a dogma for Run II. We believe that the the job of the experimenter
is to study the data and to see whether a given interesting sample can be fully
understood. At the same time, current theoretical ideas about extensions of the SM are

66 Section 2: CDF Physics Analysis
intellectually persuasive, and we recognize that a serious unbiased search for supersymmetric
particles { in particular the Higgs { is a necessity. We choose therefore to concentrate
our attention on two samples which are interesting from the SM point of view and which
eventually should be sensitive to a Higgs signal:
W +jets
two jets + missing transverse energy
It is understood that a b-tag could be applied to the jets, although not necessarily as an
initial selection criteria.
W + Jets
We consider the sample in which the W has been tagged by a high-P T lepton (electron
or muon). When there are at least two jets, then we can identify at least three interesting
contributions:
1. pp ! WW with W ! jets
2. pp ! WZ with Z ! bb
3. pp ! Wh with h ! bb.
Although the rst two are expected within the SM, they have never been observed, and a
clear signal would be a real analysis success. One might hope to study the hadronic decays of
vector bosons in pp collisions and compare to what is known from e + e , experiments, possibly
learning something about color ow. These events constitute dicult backgrounds in a higgs
search, so measuring their rates would be necessary in order to search for the higgs in this
channel. Also important in a higgs search is an understanding of di-jet mass reconstruction:
these events would provide a nice benchmark for detector and/or jet clustering calibrations.
Two Jets + Missing Transverse Energy
Without the several levels of careful clean-up procedure detailed in section 2.3.1, this
sample would be dominated by \garbage." An loose selection would yield a sample dominated
by QCD processes with mis-measured jets. But a tight selection could yield a sample
containing contributions from the following interesting processes:

Section 2: Di-Boson Production 67
1. pp ! WZ with Z !
2. ~t or ~ b pair production
3. pp ! Zh with h ! bb and Z !
4. pp ! qq with one hard parton going o into so-called \extra" dimensions
In some cases a b-tag is called for { but not in all. A sample of events with two jets and
missing energy is clearly related to the sample studied by Spiropulu & Huth in the Run I
data, but is not the same and could contain dierence signals for New Physics. Still, the
experience and in-depth understanding gained from the Run I analysis will prove invaluable
for studies of this sample.
In the following two sections we describe our plans for these studies in the context of
di-boson production and a study of 6E T + jets.
2.4.2 Di-Boson Production
(Prof. Franklin, Prof. Schmitt, Dr. Burkett, Dr. Dorigo, Mr. Hall & Ms. Madrak)
WW production. Madrak, Dorigo and Franklin have begun investigating the isolation
of a WW signal in Run II, starting, of course, with Run I data. The cross section is about
10 pb. An observation of W + W , pairs was reported by CDF in 1996 [18], using the double
leptonic topology (see Fig. 33). Although an event sample with two high P T leptons and
large 6E T is very clean, this nal state suers from a small rate due to the square of the
branching ratio Br(W ! e; ). The nal state involving one hadronic and one leptonic
W decay has never been observed at a hadron collider: the main hindrance is the irreducible
background from single W production and two jets from gluon radiation in the initial state.
This background is larger by roughly two orders of magnitude.
We think it may be possible to extract some evidence for the WW ! `jj signal in
Run I data by selecting events with a high P T lepton, 6E T , and two jets. We may study
the dijet mass spectrum after the application of kinematical selection requirements aimed at
dierentiating the QCD radiation processes from the weak W decay. The tagging of charm
jets may also constitute a useful tool to reduce the background. If we nd no signal in Run I
we can still look forward to rening and optimizing our analysis strategy, in order to be
ready to observe a clear peak with Run II data.

68 Section 2: CDF Physics Analysis
Figure 33: The pp ! WW cross section measured by CDF at 1:8 TeV compared to theory
predictions.
W + production. Another interesting diboson process is W production. CDF has
measured the cross section of this process using the leptonic decay mode of the W [19], but
no serious eort has been made in the more challenging hadronic channel. Here the data
sample is the high E T photon sample, and the primary backgrounds are + 2 jet production
and fake photons from neutral hadrons. Hall and Dorigo have begun looking at the Run I
data to determine if it is feasible to observe W 's in this sample. If a signal is found its peak
position can be used to set the energy scale for the calorimetry. Also any experience we can
gain with hadronic W decays will be useful in other related analyses.
Trileptons, and Same-Sign Dileptons. The appearance of WW and WZ events in purely
leptonic nal states is interesting, too. Schmitt identied events with three leptons (`trileptons')
or two leptons with the same sign (`same-sign dileptons') as sensitivechannels for higgs
bosons of intermediate mass (M h > 135 GeV). This comes about through pp ! Wh followed
by h ! WW () , which dominates for M h > 135 GeV. If all three W 's decay to leptons,
then a very clean topology results. (This topology has been studied already in the context
of a search for associated chargino and neutralino production.) Schmitt has developed an
eective set of selection criteria. Some examples of his cuts are shown in Fig. 34
A second clean topology arises when the two W 's with the same charge decay leptonically
with the third decaying hadronically. This topology is called the `same-sign dilepton'
topology, and due to the higher rate, is more powerful than the trilepton topology. Schmitt

Section 2: Di-Boson Production 69
completed feasibility studies which showed that the reach of the TeVatron for higgs searches
could be signicantly increased [17] on the basis of these channels. His results have been
used to derive luminosity requirements as a function of the Higgs mass, shown in Fig. 35.
The main backgrounds for the intermediate mass higgs search are WW and WZ production,
so a measurement of the rate and a study of the kinematic properties is extremely
important. Since the decays of W and Z bosons are well know, signals in these channels
would provide a powerful check on the study of the hadronic samples described above.

70 Section 2: CDF Physics Analysis
0.75
signal
7.5
signal
0.5
5
0.25
2.5
0
6
4
2
0 20 40 60 80 100 120 140
best candidate Z mass (GeV)
backgrounds
0
3
2
1
0 1 2 3 4
number of central jets
backgrounds
0
0 20 40 60 80 100 120 140
best candidate Z mass (GeV)
0
0 1 2 3 4
number of central jets
2
signal
signal
2
1
1
0
3
0 0.5 1 1.5 2 2.5 3
maximum ∆φ among leptons (radians)
backgrounds
0
2
0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1
(PT three lepton)/(PT all charged tracks)
backgrounds
2
1
1
0
0 0.5 1 1.5 2 2.5 3
maximum ∆φ among leptons (radians)
0
0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1
(PT three lepton)/(PT all charged tracks)
Figure 34: Example cuts applied in the trilepton analysis geared toward a discovery of an
intermediate mass higgs boson.

Section 2: Di-Boson Production 71
Figure 35: Integrated luminosity required as a function of the Higgs boson mass (preliminary
results obtained by the FNAL Higgs working group). The additional sensitivity for M h >
130 GeV comes from the leptonic channels relevant when h ! W + W , .

72 Section 2: CDF Physics Analysis
2.4.3 Missing Transverse Energy + Jets
(Dr. Burkett & Ms. Spiropulu)
6E T +2jets. Harvard has garnered much expertise in the use of missing transverse energy
for particle searches (see earlier discussion of the 6E T +jets search with the Run I data).
Branching out from the squark and gluino searches, we see two new topologies of interest:
1. 6E T +two jets (optional b-tag)
2. 6E T + one jet { the so-called \monojet" topology.
The natural application of 6E T +2 jets would be to stop and sbottom searches. In the latter
case b-jets would be expected so a b-tag would help reduce the background tremendously. We
recognized that these events also are sensitive to higgs bosons, through the channel pp ! Zh
with Z ! and h ! bb. Triggers designed for supersymmetric particles by Spiropulu turn
out to have avery good acceptance for higgs, too. This is discussed further below.
6E T +1jet.
Superstring theories that provide a framework of unication of all forces can describe
a real multidimensional world having a size measured in the Planck scale unit, about R =
10 ,35 m. In the vacuum state, one time and three spatial dimensions expand to the size
we observe. Each resulting tower of particles includes a massless state and its excitations
(called Kaluza-Klein) whose masses are set by the size of the compact dimensions, which
would naturally be R ,1 =10 19 GeV. The Standard Model particles are the massless states
that acquire their small observed mass from the breaking of electroweak symmetry and
supersymmetry. But there is no compelling reason why all dimensions should be either the
size of the Planck scale or the size of the observed universe - it could happen that dimensions
of the order of the weak scale (TeV or mm) arise in determining the ground state. In such
a theory the quarks and leptons are to be identied with states that have no Kaluza-Klein
excitations while the gauge bosons have a tower of excitations of mass n=R where n is
the number and R is the size of the extra dimensions. The interactions of the excitations
with quarks, leptons and gauge bosons is xed by the theory. Recently Arkani-Hamed,
Dimopoulos and Dvali [20] and in the early 1990's Antoniadis et.al have argued that the
fundamental gravitational scale can be as low as TeV energies while the size of the extra
dimensions can be as large as a millimeter. In this case gravitons should be radiated at
signicant rates in high energy particle collisions.

Section 2: Missing Energy + Jets 73
In pp collisions a signature of the massive spin-2 graviton escaping into the extra dimensions
and thus escaping detection, is large 6E T plus one jet. Peskin et al. [21] used the CDF
Run 0 analysis of events with 6E T 30 GeV and one jet (rapidity < 1:2) put a limit on graviton
production by comparing the cross section of the graviton signal and the Standard Model
processes that give such a nal state. The CDF results are based on only 4:7 pb ,1 and thus
greater sensitivity can be obtained simply by studying the data from Run I. Fig. 36 (from
hep-ph/9811337) shows the 6E T
background.
spectrum of the graviton signal and the Standard Model
Fig. 36 shows the 6E T distribution of a subset of the CDF Run Ib 6E T data sample and with
the requirement of exactly one jet. The main backgrounds is Z QCD associate production
where the Z decays to , W production where the W decays to a tau lepton and a neutrino
and residual QCD background from mismeasurements and jet resolution. By raising the 6E T
rrequirement to 60 GeV and estimating the Standard Model backgrounds we expect to be
sensitive to the graviton production process in the 6E T plus monojet channel.
The reach in the (size of extra dimension, eective Planck scale) plane, compiled based
on the study of Peskin etal: and for LEP2, TeVatron, TeV II, Linear Collider (LC) and LHC
is given for number of extra dimensions N=4,6 (which are favored cosmologically) in Fig. 37.

74 Section 2: CDF Physics Analysis
E/ T (GeV)
Figure 36: (Top) Spectrum of 6E T in events with one jet [21]. The dotted curve is the Standard
Model expectation. The solid curves show the additional cross section expected in the model
where the graviton escapes into the extra dimensions with (a) Number of extra dimensions
N =2and eective Planck scale M = 750 GeV and (b) N =6and M = 610 GeV. (Bottom)
Spectrum of 6E T in events with one jet from a subsample of Run Ib data.

Section 2: Missing Energy + Jets 75
Figure 37: Reach for N = 4 (top) and N = 6 (bottom) of various present and future
experiments.

76 Section 2: CDF Physics Analysis
2.4.4 Missing Energy Trigger
(Prof. Huth & Ms. Spiropulu)
The 6E T trigger drives a number of analyses and the need for a carefully designed 6E T
trigger for the Run II luminosity environment is evident. A few of the physics processes that
can be studied with a data sample triggered by large energy imbalance are the following:
Vector boson production and leptonic decays. Although there is a dedicated 6E T plus
lepton trigger for the study of the W boson, W QCD associate production remains
a crucial background for a number of New Phenomena searches and the 6E T plus jets
trigger provides a good sample to study this as well as the W to process. For Z
production and decay, the 6E T sample provides a dataset to measure directly the Z to
cross section. Furthermore again, Z boson QCD associated production is a background
to many New Phenomena searches.
Top quark production and decay to W and b quark. The 6E T
alternate dataset to measure the top cross section.
trigger provides an
Associate Higgs W and Higgs Z production. The 6E T combined with a b quark tagging
or a tau lepton tagging trigger can provide a highly ecient triggering scheme for the
discovery of the Higgs boson.
New Phenomena searches. Just to mention a few, the 6E T trigger can be used to search
for
{ supersymmetric partners: Supersymmetry, or minimal Supergravity inspired
models usually contain the Lightest Supersymmetric Particle(LSP) in the nal
state of the decays of the superparticles. The LSP escapes the detector and
appears as energy imbalance. Examples are squark and gluino searches, scalar
top and scalar bottom searches.
{ Gravitinos:In Gauge Mediated Supersymmetry Breaking scenarios that incorporate
gravity the Lightest Supersymmetric Particle is the gravitino { the 3/2 spin
partner of the graviton. The gravitino goes undetected and produced huge energy
imbalance. In recent Gauge Mediated scenarios with very light gluino being the
LSP, 6E T plus jets isafavored signature.

Section 2: Run II Triggers 77
{ Leptoquarks where the leptoquark decays in a quark and a neutrino
{ CHArged Massive Particles (CHAMPS): These are long-lived massive particles
that if they are penetrating enough can go undetected and cause energy imbalance.
{ Gravitons In Kaluza-Klein-type string theories of extra dimensions (where the
extra dimension is physical but has compactied in the sense that for example
the universe in this dimension is small compared to the smallest distances probed
by experiments) the graviton can be produced in high energy hadron collisions
and escape to the extra spatial dimension thus creating an energy imbalance in
the usual 3 spatial dimension space.
The study for the design of the 6E T trigger for Run II is using data from Run Ib. We
calculate the rates for an inclusive 6E T trigger as well as a 6E T plus jets multilevel trigger. At
the lower level (L1) the trigger requires 6E T > 25 GeV. At Level 2 (L2) the 6E T requirement
remains the same and two jets of energy 10 GeV are required (we call it \L2 MET" trigger).
At Level 3 (L3) the 6E T requirement is raised to 35 GeV. Compared to the RunI 6E T trigger,
the rates are about the same although the luminosity is going to be signicantly higher at
Run II. This is because although we lower the L2 6E T threshold from the previous run (30
GeV) the Main Ring that was responsible for more than one third of 6E T triggers at RunI
does not longer exist. In the case of very high luminosity environment the 6E T threshold
would need to be raised. The total trigger rate budget allows for an inclusive L26E T trigger
of 45 GeV which would catch monojet events, photons and other potentially exotic events.
For the L2 MET trigger we present the signal eciency for the following processes:
SUSY, 300 GeV gluinos The upper left plot of Fig. 38 shows the L2 6E T trigger
eciency for squark gluino production as a function of the 6E T trigger threshold and
for the case of inclusive 6E T (solid triangles), of two jets of 6 GeV requirement (open
squares), and two jets of 10 GeV requirement (open circles). The L2 MET trigger for
this SUSY point is more than 90% ecient.
top quark production. The upper right plot of Fig. 38 shows the L2 6E T Trigger
eciency as a function of the 6E T trigger threshold. The L2 MET trigger for top (which
is decaying inclusively) is about 60% ecient.
W/Z Higgs associate production with the subsequent decay channels and Higgs mass
as denoted in the bottom plots of Fig. 38. The L2 MET trigger is between 55% and
65% ecient depending on the process and the decay channels.

78 Section 2: CDF Physics Analysis
Figure 38: Level 2 6E T trigger eciency for Run II and for dierent physics processes (to
read the eciency follow the open circle curves and their value for 6E T of 25 GeV).

Section 2: Run II Triggers 79
2.4.5 Multijet Trigger for W=Z + h
(Prof. Huth, Dr. Maksimovic, Dr. Riegler & Mr. Medvigy)
In his search for the Standard Model Higgs boson produced in association with a vector
boson (W or Z) in the Run I multijet data, Jorge Troconiz (then a post-doc in our group)
encountered problems with the old multijet trigger. The trigger was optimized for tt ! 6
jets, and involved only the second level of CDF's three-level trigger system. In Run Ib, the
multijet trigger had to satisfy the following criteria:
at least four Level 2 calorimeter clusters with E T > 15 GeV
total Level 2 calorimeter energy (sum over all clusters) P E T > 125 GeV
The fundamental challenge for Troconiz's Higgs search was that the above criteria were
rather inecient for the light SMHiggs. Furthermore, the trigger eciencies for H + W=Z
signal corresponding to Higgs masses between 90 and 140 GeV (that the search considered)
were found to vary signicantly { i.e., the Run I search ended up right on a steep part of
the trigger eciency curve.
In this situation, there clearly is room for improvement, and the natural place to do so is
in the calorimeter requirements of the multijet trigger. Professor Huth initiated this project
by advocating the idea of using displaced tracks found by the secondary vertex tracker (SVT)
P as a means of controlling the increase in the trigger rates caused by the lowering of the E T
requirement.
In the redesign of the multijet trigger { so that it is appropriate for a H + W=Z search
{ our goal is to dene trigger criteria that are ecient for the type of events we would like
to collect after all selection cuts, including both trigger and oine. For instance, in order to
form the invariant mass of a Higgs candidate, we need to be able to identify the b jets in a
multi-jet event; therefore we expect that we will have to employ some form of b-tagging. The
events that fail the oine version of the b-tagging (currently approximated by SECVTX)
are therefore of no use for us, and we ignore them while tuning the multijet trigger. We
therefore try to
1. keep the eciency of two b-tags at the oine level as high as possible;
2. keep the trigger rates (dominated by background) as low as possible.

80 Section 2: CDF Physics Analysis
We do not optimize on the basis of single number, such asS=B or S 2 =(S +B), since there is a
danger of being locked in a nonoptimal data point once new cuts are introduced a posteriori.
First Pass
Post-docs Petar Maksimovic and Werner Riegler were instrumental in carrying this study.
The initial changes to the Multijet trigger were suggested by the distributions of the Level 2
cluster quantities from both H + W=Z Monte Carlo and data. Since it was soon apparent
that the leading jet in H + W=Z events almost always has E T > 20 GeV, as a background
sample we perused the so-called \Jet 20" data, a Run I sample with at least one cluster with
E T
> 20 GeV required at Level 2. The signal sample is a Pythia Monte Carlo, simulated
through P the full Run I detector simulation. Fig. 39 shows the distributions the number of
jets, E T , and E T of the four highest-E T jets from W=Z +H Monte Carlo (solid) (generated
with m H = 110 GeV), and the Jet 20 data (dashed), normalized to the same area.
Motivated by the shapes of these distributions, we modied the old multijet trigger in
the following way:
1. We expect four jets in the WH or ZH event. Since not all jets are reconstructed, and
some are merged with others, we nd the requirement of four jets too restrictive, and
relax it to three.
2. We also relax the Level 2 P (L2) E T cut to 70 GeV.
3. To these kinematics cuts, we add the requirement of at least one displaced SVT track
at Level 2, and at least two SECVTX tags at Level 3.
Fig. 39 shows the comparison of the relevant distributions between the W=Z + H Monte
Carlo (solid) and the Jet 20 (dashed).
Run II trigger simulation of the calorimeter response
In order to study calorimeter requirements (which are fundamental for this trigger), we
utilized the Run II trigger simulation developed by the Run II Trigger Working Group.
The trigger simulation was applied to both signal Monte Carlo and to Jet 20 data (based
on the oine jet information). Given the importance of Level 2 criteria, we rst varied the
P
(L2) E T threshold, as well as the cuts on E T of individual jets, and examined the dependence

Section 2: Run II Triggers 81
30000
3000
20000
2000
10000
1000
0
0 2 4 6 8 10
0
0 100 200 300
4000
6000
3000
2000
1000
4000
2000
0
0 25 50 75 100
0
0 25 50 75 100
6000
6000
4000
4000
2000
2000
0
0 25 50 75 100
0
0 25 50 75 100
Figure 39: The relevant distributions from W=Z + H Monte Carlo (solid), and the \Jet 20"
data (dashed), normalized to the same area.

82 Section 2: CDF Physics Analysis
of signal eciencies (based on Pythia Monte Carlo) and the background rates (based on \Jet
20" data).
In addition, in Run II every trigger has to have a full path (i.e., specied criteria at all
trigger levels), so we also place a cut on Level 1 P (L1) E T . While P (L2) E T is a sum of found
P calorimeter clusters, (L1) E T is just a sum over trigger towers above a threshold; the two are
physically dierent quantities, the latter being much more sensitive to underlying event and
pile-ups. The threshold for Level 1 sum is still under negotiations in the Trigger Working
Group (currently 1 GeV), with us favoring higher values.
P Fig. 40 shows the eciencies and the rates as a function of (L2) E T given the calorimeter
cuts at Levels 1 and 2, plus a requirement for two b-tags at Level 3.
The Use of Tracking
The lowering of the Level 2 calorimeter cuts necessarily increases the rate for the multijet
trigger. As outlined above, we cut the rate down by making use of the tracking devices
implemented in hardware: eXtremely Fast Tracker (XFT, operating on COT data at Level 1)
and Silicon Vertex Tracker (SVT, operating on SVXII data { seeded by XFT {atLevel 2).
The XFT-SVT combination provides measurements of p T , and d 0 for reconstructed tracks.
We assume that the set of \XFT tracks" (approximated by CTC tracks of Run I data)
that are reconstructed in the SVX', is a good approximation of an \SVT track" sample. We
studied the eciencies and the rates as a function of the number of XFT-SVT tracks, the
number of displaced tracks, and the displacement for a xed number of `displaced' tracks.
We found that a cut on d 0 > 150m ontwo or more tracks, or d 0 > 100m on three or more
is benecial.
Future Work
In order to complete this study in the near future, we plan to focus on
1. A combined simulation of XFT and SVT: A package consisting of XFTSIM and
SVTSIM is available, but awaits the SVX' alignment les from the SVTSIM experts for
Jet 20 data. Nonetheless, it is being claimed that the resolutions on p T and d 0 are
comparable to those of the Run I oine, so we expect the nal results to be similar to
our current estimates based on Run I data.
2. b-tagging in trigger using leptons: we will add lepton information as another basis

Section 2: Run II Triggers 83
Level1: ΣE t
>80GeV
100
90
80
70
60
50
40
30 Level2: ΣE t
>Abscissa
20
10
0
60 80 100 120 140
8
7.5
7
6.5
6
5.5
5
4.5
Level3: ≥2SecVtx Tags
4
60 80 100 120 140
100
80
60
40
20
0
60 80 100 120 140
0.6
0.5
0.4
0.3
0.2
0.1
0
60 80 100 120 140
Figure 40: Eciencies and rates vs. P E T cut.

84 Section 2: CDF Physics Analysis
LVL1 ΣE t
>70GeV,LVL2 nj≥2 j1>20 j2>20,NXFT Tracks > 12, >2 SVT Tracks d 0
> Scan, LVL3 ≥2 SECVTX
10 2
10
0.005 0.0075 0.01 0.0125 0.015 0.0175 0.02 0.0225 0.025 0.0275 0.03
10 2
10
1
10 -1
10 -2
0.005 0.0075 0.01 0.0125 0.015 0.0175 0.02 0.0225 0.025 0.0275 0.03
Figure 41: The signal eciency (top) and the rate (bottom) as a function of the impact
parameter (d 0 ).

Section 2: Run II Triggers 85
for b-tags. The B group plans to make use of leptons with p T as low as 2 GeV/c. The
leptonic information is used at Level 1, which only reduces the rate compared to our
`default' (SVT-based) tagging option. At the Level 2, due to B meson semileptonic
branching fractions, the lepton trigger is comparable to a trigger based on displaced
tracks from SVT. The missing bit of information is the eect of the muon fakes and
electron conversions (the inner detector has more matter in Run II, and the conversion
rate is expected to increase compared to Run I data). Student David Medvigy is also
involved in this study.
We envision a combined SVT-based and lepton-based trigger, that uses the lepton info
at Level 1 if it is available, and then meshes the leptonic and displaced-track tags at
Level 2. We plan to set the cuts on displacement(jd 0 j) and lepton p T so that they are
almost interchangeable, and in that way dene one dataset comprising of SVT-SVT,
SVT-lepton and lepton-lepton b-tags.
3. b-tagging algorithms at Level 3: our current work is based on two SECVTX tags
at Level 3. However, we consider SECVTX to be `destructive', in a sense that it has
high purity at the expense of signal eciency. We would prefer to use an algorithm
more ecient for the H + W=Z signal at Level 3, allowing for more maneuvering room
oine.
4. b-jet mass resolution: the di-jet mass resolution is crucial for the sensitivity to higgs
signals. As discussed in the next section, advances there will improve the performance
of this trigger, too.
5. Oine analysis: There are two levels of involvement:
(a) Use existing Run I code and SECVTX tagging to update the Run I limit in the
light of the change in the trigger.
(b) Update the limit using the Run II software tools. This would also prepare us for
the Run II data, and may feed back into the Level 3 b-tagging algorithms, which
will also be based on the Run II software tools.
In conclusion, although there are several technical issues that still remain to be settled,
we have veried that the fundamental ideas behind this trigger are sound, and that such a
trigger is viable in Run II.

86 Section 2: CDF Physics Analysis
2.4.6 Di-Jet Mass Resolution
(Prof. Schmitt & Dr. Dorigo)
Our ability to extract a higgs signal over a large QCD background depends critically on
the resolution we can attain on the mass as calculated directly from the two b-jets. If the
resolution is poor, then it will be dicult to observe a peak from the higgs in the dijet mass
spectrum. The better the resolution, the smaller the mass window we can dene for a signal,
and the smaller the number of background events for a given luminosity.
The expected resolution for a jet-jet resonance in Run I was roughly Mjj =0:1 M jj . A
relative improvement of this number by 30% would signicantly extend our discovery reach
for the Higgs boson in Run II (see for example Ref. [17]). In order to achieve that improvement
we must study in detail the characteristics of b-quark jets emitted in the Higgs
decay, and exploit fully the information provided by the all relevant detector components.
For example, three-dimensional tracking in the new SVX II detector will allow us to infer
the momentum of the escaping neutrinos in semileptonic b-quark decays, greatly improving
the energy measurement of the resulting jets. This plan will work well in Run II, given the
larger acceptance for charged leptons from semileptonic decays provided by the new plug
calorimeter and the completion of the central muon system. Furthermore, the possibility
of measuring track momenta up to a rapidity jj = 2:0, thanks to the new COT and silicon
detectors, will allow a fruitful use of tracking information to improve the calorimetric
measurement of jets.
While searching for evidence of Z ! bb decays Dorigo succeeded in improving the dijet
mass resolution for b-jets. He found that the most useful quantities were the muon
momentum, the projection of missing transverse energy along the jet axes, and the charged
fraction of the jets. The muon momentum is needed in the correction of the jet originated
from the semileptonic decay of the parent b-quark, because the minimum ionizing muons do
not contribute linearly to the energy measured in the calorimeter. The missing E T , projected
along the jet directions in the transverse plane, provides useful information on the neutrino
momentum and on possible uctuations of the energy measurement. The charged fraction of
the jets, dened as the ratio between the total momentum of charged tracks belonging to a
jet and the energy measured in the calorimeter, also helps to reduce the error in the energy
measurement. By properly accounting for the value of these observables, it was possible to
reduce the resolution of the dijet mass, M =M jj , by nearly 50% (see Fig. 42).

Section 2: Di-Jet Mass Resolution 87
We are presently studying the application of these methods to search for a Higgs boson
signal in Run II.
PYTHIA Z → bb: Mass Reconstruction
2500
2000
All Corrections
µ and Missing E T
Corrections
µ Corrections
Standard Corrections
Constant 2367.
Mean 90.01
Sigma 12.27
1500
1000
500
0
20 40 60 80 100 120 140
Dijet Invariant Mass (GeV/c 2 )
Figure 42: The four gaussian ts show the improvement of the mass reconstruction for
simulated Z ! b b events (PYTHIA V5.7) when the observable characteristics of the b-quark
decays are properly taken into account in the mass reconstruction.

88 Section 2: CDF Physics Analysis
2.4.7 B Mixing and CP Violation
(Prof. Huth, Dr. Maksimovic & Mr. Bailey)
In the next few years several experiments will come online with the intention of detecting
and measuring CP violation with B mesons in several decay modes. These include dedicated
B factory experiments such as Belle and BaBar as well as hadronic experiments such as CDF.
CDF has already demonstrated its potential to measure B sector CP violation with the recent
measurement of the CP violating parameter sin(2) =0:790:390:16 [24] using the decay
mode B 0 ! J= K s in the Run I data. This analysis used a B 0 avor tagging algorithm
developed by Maksimovic for his thesis. CDF II should be able to signicantly improve this
measurement as well as measure other CP violating parameters with other decay modes.
The Harvard group will be involved with these studies, especially those involving B s mesons.
The group has interest in CP violation studies using B s ! Ds K and B s ! J= as well
as the requisite measurements of B s mixing and avor tagging. Contributions have already
been made in the area of a signal to background study, avor tagging algorithms, and a
feasibility study for B s ! Ds K .
These B physics interests are directly related to our work on the Silicon Readout Controller
(SRC) for the Silicon Vertex Detector data acquisition system (SVX DAQ). The SVX
DAQ is designed to process a 40 kHz level 1 accept rate and trigger on B events at level
2. This ability is unique to CDF and is crucial to acquiring a large and pure B sample for
performing these B physics studies.
The Unitarity Triangle
In the Standard Model, CP violation arises from a single complex phase in the V CKM
mixing matrix which relates the quark mass and weak eigenstates. By treating the elements
of the unitarity relation
V ud V
ub + V cd V
cb + V td V
tb =0
as vectors in the complex plane, one may form the \unitarity triangle" which neatly summarizes
the relevant parameters in B meson CP violation studies. Dierent decay modes of
B mesons produce CP violating eects proportional to the sine of various combinations of
these angles.

Section 2: B Mixing and CP Violation 89
6
(; )
V ud V ub
V cd V
cb
V td V
tb
V cd V
cb
arg , V tdV
tb
b bbbbbbbbbb
b
(1; 0) -
V ud V ub
arg , V cdV
cb
V td V
tb
arg , V udV ub
V cd V
cb
Many new physics scenarios (e.g. SUSY) predict alternate forms of CP violation which
would aect these measurements [25]. One possibility is that the new physics would introduce
new phases such that the measured + + would not equal 180 . These new phases would
also aect B 0 decays dierently than B s decays and thus the same angle measured with two
dierent decays could produce dierent results. Another possibility is that no new phases
would be introduced but that the magnitudes of B 0 and B s mixing would be increased such
that the measured sides of the unitarity triangle would not be consistent with the measured
angles. Thus measuring CP violation with a variety of B decays provides a rigorous test
of the Standard Model's explanation of CP violation as well as a sensitive probe for new
physics.
Mixing Induced CP Violation
The form of CP violation which is most useful for constraining the Standard Model is
due to mixing between B 0 and B 0 , or B s and B s . For nal states to which both particle
and anti-particle can decay, interference can arise due to phase dierences between the two
decay channels. Considering the decay B s ( B s ) ! D s , K + for example, the V CKM elements
for B s ! D s , K + are approximately real as are the elements for the B s ! B s mixing. But
the V CKM phase of B s ! D s , K + is approximately the angle of the unitarity triangle. The
time dependence of the B s mixing produces a time dependent CP violating parameter of
magnitude sin .
real
-
B s D , H K+ s
HHHHHj
*
real
B s

90 Section 2: CDF Physics Analysis
Bs
Ds K
φ
π
K K
Other B Decay (used for tagging)
000 111
000 111
000 111
000 111
Primary Vertex
Bs
Ds
Fragmentation K (used for tagging)
K
Figure 43: Diagram of the B s ! D s K; D s ! ; ! KK decay, including fragmentation
K and opposite side B used for avor tagging.
Measuring sin with B s ! D s K
Bailey has performed a feasibility study for measuring sin using the decay mode B s !
Ds K at CDF II. Since then, he and Maksimovic have improved this study and presented
it to the collaboration. This mode is unique to hadronic colliders (the B factories do not
produce B s ) and thus provides an important complement to studies using B 0 . It also has the
benet of not involving \penguin" diagrams which make many CP violation measurements
ambiguous through their non-CP violating contributions. With a relatively large decay rate,
B s ! Ds K is one of the best decay modes for measuring sin which is necessary for the
full consistency check of the Standard Model.
The theoretically expected errors are inversely proportional to a variety of dilution factors
which eectively reduce the amplitude of the signal observed. These dilution factors arise
from measurement resolutions, backgrounds, t limitations, and avor tagging ineciencies
and mistags. Using the latest CDF II estimates for these dilutions the expected error on
sin is 0.45.
To check the dependence of this measurement upon various input parameters, Bailey
wrote a toy Monte Carlo simulation and likelihood tter including backgrounds, resolution
eects, and mistag probabilities. The measurement involves an unbinned likelihood t to
four dierent decay rates (both B s and B s to both D s , K + and D s + K , ) to extract the weak
phase , a strong phase, and the ratio of the decay rates. The input parameters to the event
generation and t were varied and the resulting error on sin was studied. It was found
to scale as expected by theory. Figure 45 (left) shows the expected error as a function of
the B s mixing parameter x s = m s =,. The current limit on m s is 10:2ps ,1 [26], but

Section 2: B Mixing and CP Violation 91
N(B s
-> Ds - K + )
30
25
20
15
10
5
0
0 0.2 0.4 0.6 0.8 1
proper time
Figure 44: Example t to the proper time distribution of B s ! D s , K + . This distribution is
t simultaneously with B s ! D s + K , , Bs ! D s , K + , and B s ! D s + K , to extract the CP
violating parameter sin . Note that the actual t is an unbinned t; the binned nature of
this plot is for visualization purposes only.

Section 2: B Mixing and CP Violation 93
oscillation frequency, m s . Additionally, new physics contributing to the B s mixing `box'
diagram would cause a larger m s than Standard Model predictions even if the new physics
does not aect the angles of the unitarity triangle. Therefore, it is imperative to measure
m s as a prerequisite for any serious testing of the self-consistency of the CKM matrix.
To measure the B s oscillation frequency, one needs
1. proper time of the B s decay
2. decay avor of the B s meson, obtained from the B s decay products
3. production avor of the B s meson, inferred either from the decay products of the other
b-quark in the event (in pp collisions, b b are produced in incoherent pairs), or from the
byproducts of the b ! B s hadronization; this process is called avor tagging.
In preparation for the B s mixing measurement, the Harvard group is involved in the
following tasks:
Generic decay reconstruction tool: Postdoc Maksimovic wrote a generic tool able
to reconstruct an arbitrary decay.
Study of combinatorial background for the PAC: Maksimovic utilized this tool
to isolate a sample of events with a lepton and a D s decay in the opposite hemisphere
(to or K K), which provided a basis for a study of combinatorial background in
fully reconstructed B s ! D s (n) events, conrming the prior estimate of S=B between
1:2 and 2:1.
Vertex nding in D s X events: Maksimovic isnow focussed on investigating a technique
to nd the decay point ofaB s ! D s X decay using new Run II software framework
and tools adapted to Run I data.
Since the B s production avor is determined by the sti trigger lepton in the opposite
hemisphere (characterized by avery high purity of the avor tag), the B s decay vertex
is the only ingredient missing in a B s mixing analysis. Given that D s X sample is a
superset of D s (n) sample designated for B s mixing, this approach has a potential to
be the rst analysis to actually measure m s in Run II.
Other tagging studies: Maksimovic isinvolved in other studies of the `opposite side
tagging' (avor tagging involving decay products of the b-hadron in the opposite hemisphere),
using the samples of B 0;+ ! `+D () decays.

94 Section 2: CDF Physics Analysis
D s
→ φπ, φ → K + K - / OS lepton
Events / 10 MeV
120
100
80
60
40
130 ± 25 events
20
0
1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2
m(φπ) (GeV)
Figure 46: Mass plot of D s ! ; ! K + K , with an opposite side lepton which could be
used for a B avor tag.

Section 2: B Mixing and CP Violation 95
Generic tting tool (FitFramework): Given the similarity between the unbinned
likelihood ts for lifetimes, mixing, CP violation in J= K S () and B s ! D s K, Maksimovic
and Bailey created a framework that maximizes code recycling across avariety
of ts, thereby allowing them to keep all Run II physics options open.
Most of the above activities are interconnected, and all feed not only to B s mixing
analysis, but also to the measurement of sin in B s ! D s K, and further into some other
interesting analyses we may consider in the future, such as measuring CP asymmetry in
B s ! J= .

96 Section 2: CDF
2.5 Synopsis
We are working on three major hardware upgrade projects:
COT: The COT replaces the CTC which would be inadequate for the higher luminosities
of Run II. We are building much of the actual chamber and are responsible for
testing and calibrating it. We will soon begin working on the new online and oine
software required for this new device.
SVX: The new SVX will be much longer and will provide 3D tracking. We have
designed and fully debugged the readout controller (SRC) and are now writing and
debugging much of the software required for data acquisition.
CMX: The CMX coverage was incomplete in the last run. To complete it, we are
installing chambers where the Main Ring used to pass over the detector, and in the
lower 90 in azimuth beneath the nominal oor. We are involved in rewriting the oine
code and will become involved in the online soon.
Our recent successes in the analysis of Run I data include two very important measurements
and apowerful search for Supersymmetry:
top cross section: A new and much improved measurement of pp ! tt has been
approved for publication by the collaboration.
W mass: We have completed the nal measurement of the W mass in the electron
channel, which will be published together with the muon channel this summer.
6E T + jets: Our control of the 6E T measurement has greatly increased the sensitivity
of this channel to physics beyond the Standard Model. A result is expected soon.
We are shifting much of our analysis eorts toward Run II. Some of current plans and
activities include:
di-boson production: The W +Jets and 6E T +Jets samples will contain contributions
from WW and WZ production. They may also be windows to New Physics, including
the Higgs boson.
monojets: We will apply our expertise in 6E T measurement to a monojet search. A
null result would constrain theories of electroweak-gravity unication via large extra
dimensions.

Section 2: CDF 97
multijet trigger with b-tag: We are developing a trigger to allow alarge sample of
b-tagged multijet events. These events could contain a signal for W=Z + h.
6E T trigger: We have stated the requirements for an eective 6E T +jets trigger which
is sensitive, among other things, to supersymmetric particles and higgs.
B s Mixing: There are currently only limits on the frequency of B s mixing. We
are working with other groups to prepare the CDF analysis which will measure this
frequency in Run II.
CP Violation: We have devised analyses which will enable a measurement of the
CP-violation parameter . This exploits the unique opportunity of a hadron collider
to study the B s as opposed to the B d .
This group is active in many areas yet is cohesive and shares all resources, meeting weekly
to discuss issues in specic hardware or analysis projects as well as general issues coming
from the CDF experiment.

98 Section 2: CDF
Publications
Below we list publications for which a member of the group was an author. The list is
in reverse chronological order.
1999
A Measurement of the W Mass, draft in preparation for Physical Review. Gordon
New Tevatron Results on the W Mass, T. Dorigo, proceedings for the XXIV Rencontres
de Moriond, March 1999. Dorigo
Measurement of the Bs 0 Meson Lifetime Using Semileptonic Decays, Phys. Rev. D59
(1999) 032004. Burkett
Measurement of the B 0 , B 0 avor oscillation frequency and study of same side avor
tagging, Phys. Rev. D59 (1999) 032001. Maksimovic
1998
Search for Higgs Bosons Produced in Association with a Vector Boson...,
Phys. Rev. D81 (1998) 5748. Troconiz
Measurement of the Charm Contribution to the Structure of the Proton, draft in preparation.
Rowan Hamilton, Huth
Measurement of the Top Quark Mass and tt Production Cross Section from Dilepton
Events..., Phys. Rev. Lett. 80 (1998) 2779. Ptohos, Jacobo Konigsberg
Measurement of the tt Production Cross Section..., Phys. Rev. Lett. 80 (1998) 2773.
David Kestenbaum, Franklin
Measurement of the Top Quark Mass, Phys. Rev. Lett. 80 (1998) 2767.
Jacobo Konigsberg, Franklin
Search for Flavor-Changing Neutral Current Decays of the Top Quark
Phys. Rev. Lett. 80 (1998) 2525. Robin Coxe, Franklin

Section 2: CDF 99
The Jet Pseudorapidity Distribution in Direct Photon Events...,Phys. Rev. D57 (1998)
1359. Huth
1997
Search for New Particles Decaying into bb and Produced in Association with W Bosons
Decaying into e and ... Phys. Rev. Lett. 79 (1997) 3819. Ptohos, Franklin
Measurement of Double Parton Scattering... Phys. Rev. Lett. 79 (1997) 584. Huth
Search for Third Generation Leptoquarks in Two-Jet Events..., Phys. Rev. Lett. 78
(1997) 2906. Thomas Baumann, Franklin
1996
The SVX II Silicon Vertex Detector Upgrade at CDF, Nucl. Instrum. Meth. A383
(1996) Spiropulu, Gay, Oliver, Huth
Measurement of Dijet Angular Distributions Phys. Rev. Lett. 77 (1996) 5336. (erratum,
78 (1997) 4307) Huth
Inclusive Jet Cross-section..., Phys. Rev. Lett. 77 (1996) 438. Huth
The Discovery of the Top Quark, by Melissa Franklin and Claudio Campagnari,
Rev. Mod. Phys. 69 (1997) 137.
1994
Search for the Top Quark Decaying to charged Higgs..., Phys. Rev. Lett. 72 (1994)
1977. Colin Jessop, Franklin
Evidence for Top Quark Production..., Phys. Rev. D50 (1994) 2966. Huth
Evidence for Top Quark Production..., Phys. Rev. Lett. 73 (1994) 225. Huth

100 Section 2: CDF
Godparenting
The task of \godparenting" a CDF draft publication is a large responsibility and requires
major eort. In the view of the collaboration, the validity of the result rests as much with
the godparents as with the authors. The Harvard group often contributes by serving as
godparents.
Schmitt Study of inclusive leptons and dimuon invariant mass distributions. Recent
studies of inclusive leptons in heavy quark jets have shown poor agreement with the
simulation. There is much work to be done to get at the source of the discrepancies
and to evaluate their signicance.
Dorigo Properties of Jets in Top Decays. This analysis is controversial and has not yet
materialized in the form of a draft paper. It is based on the work documented in the
Ph.D. thesis of Ptohos.
Dorigo started godparenting in December 1998. A key piece of the analysis relied on
Kolmogorov-Smirnov tests between the top jets and control samples. Dorigo validated
these comparisons with his own code. He also reviewed the technical aspects of the
b-tagging and how its eciency is estimated from the data, which is also a key point.
This estimate has been very dicult to obtain and impacts on the measurement ofthe
tt cross section. The godparent report is nearly nished and the authors can begin
writing a draft.
Spiropulu Tests in Perturbative QCD in W Boson plus Jets Events. This analysis has
been performed by a competent group. Spiropulu has analyzed a similar sample of
events are part of the background studies for her 6E T +Jets analysis, and so she can
provide a more \inside" viewpoint onthis analysis.
Schmitt W mass measurement. This analysis was plagued by diculties in setting
the energy scale for the electrons. The exhaustive studies by Gordon had shown that
there was no simple, easy explanation for the discrepancies between the so-called \E/p
method" and the \M Z method" (see Section 2.3.3). Excellent work in modeling and
calibration had been completed, and also the muon channel was well advanced.
Schmitt was invited to join a group of four godparents who advanced this analysis from
inaction to publication. It was decided that the scale would be set using the Z mass,

Section 2: CDF 101
while the problems of the electron energy scale, themselves very interesting, would be
an important part of the publication.
Burkett Measurement of the B 0 B 0 Oscillation Frequency Using `D + Pairs and Lepton
Flavor Tags. Burkett comments on the analysis and is responsible for the clarity and
style of the writing.
Franklin Measurement of the W asymmetry. Franklin is an expert in W physics at
the Tevatron and was a chief critic of some aspects of this analysis. This result is
very important in the determination of proton structure functions, which in turn are
important for the W mass measurement and many other electroweak studies.
Dorigo A Measurement of the Dijet Mass Dierential Cross Section in pp collisions
at p s = 1:8 TeV. Dorigo started godparenting this paper in October 1998. This
paper looked initially to be in good shape as the analysis relies largely on established
techniques. Dorigo, however, studied a weak assumption on the location of the primary
vertex, demonstrating that it was wrong 10% of the time. Correcting this improved
the estimate of the selection eciency as a function of dijet mass. Dorigo's criticisms of
the statistical method has spurred an improved chisquare method which is still under
development. Once this is nished a draft should be ready within a month.

102 Section 2: CDF
student advisor year abbreviated title
Andrew Scott Gordon Franklin 1998 A Measurement of the W Boson Mass...
Fotios K. Ptochos Franklin 1998 Measurement of the tt Production Cross Section using Heavy Flavor Tags...
David Samuel Kestenbaum Franklin 1996 Observation of tt Production using a Soft Lepton Tag...
Rowan T. Hamilton Huth 1996 Measurement of Photon-Charm Production...
Thomas Patrick Baumann Franklin 1996 A Search for Third Generation Leptoquarks...
Colin Phillip Jessop Franklin 1993 A Search for the Top Quark decaying to the Charged Higgs Boson...
Johnny Shing Tung Ng Feldman 1991 Measurement of the Z Boson Transverse Momentum...
Edward Thomas Kearns Franklin 1990 Z 0 Production Cross Section...
William Trischuk Schwitters 1990 A Measurement of the W Boson Mass...
Robert Matthew Carey Schwitters 1989 Angular Distributions of Three-Jet Events...
David Nathan Brown Schwitters 1989 A Search for Double Parton Interactions...
Richard Dante St. Denis Schwitters 1988 Dijet Angular Distributions...
Table 7: Completed Ph.D. Theses. (Phrases such as \in Proton-Antiproton Collisions at the Fermilab Tevatron" have been
suppressed for brevity.)

Section 2: CDF 103
Talks at Conferences and Workshops
M. Schmitt, SUSY Searches at LEP, (invited review talk) Higgs and Supersymmetry
Conference, Gainesville, FL., March 1999.
T. Dorigo, New Tevatron Results on the W Boson Mass, Les Rencontres de Moriond,
Les Arcs, March 1999.
T. Dorigo, Prospects for Z ! bb in Run II, Run II Workshop on QCD and Weak Boson
Physics, Fermilab, March 1999.
R. Madrak, Mechanical Design of the CDF Central Outer Tracker, APS, Atlanta, GA.,
March 1999.
C. Hall, Operation of the CDF Central Outer Tracker during Tevatron Collider Run
II, APS, Atlanta, GA., March 1999.
M. Spiropulu, Beyond the Standard Model at the Tevatron, Aspen Winter Conference
on Particle Physics, Aspen, CO., January 1999.
M. Spiropulu, On experimental prospects for nding SUSY at CDF/D0, SUSY/Higgs
Workshop, Fermilab, September 1998.
P. Maksimovic, Future Prospects for Measurements of CP Violation at CDF and D0,
Workshop on CP Violation, Adelaide, Australia, 1998.
S. Bailey, The Silicon Readout Controller (SRC) of the CDF II Detector, APS, Columbus,
OH., 1998.
J. Troconiz, B Physics, 2nd Latin American Symposium on HEP: San Juan, PR, 1998.
C. Gay, B Physics, Hawaii, 1997.
M. Spiropulu, SUSY with Missing Transverse Energy at CDF, APS, Washington, D.C.,
1997.
A. Gordon, Preliminary Measurement of the W Mass in the Muon Channel...,
Moriond, 1997.

104 Section 2: CDF
J. Troconiz, B Physics at the Tevatron Collider, Moriond, 1997.
Franklin, The Top Quark, a series of ve academic lectures given at CEN, 1996.
D. Kestenbaum, Top with a Soft Lepton Tag, 1996
C. Jessop, Search for Charged Higgs in Top Decays, Physics in Collision, 1995.

Section 2: CDF 105
References
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http://www-bd.fnal.gov/lug/ .
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106 Section 2: CDF
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