E - opera - Infn

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E - opera - Infn

The OPERA experiment

• The physics programme

• The startup of CNGS

• Very first events in OPERA

• Status of construction and the 2007 run

F.Terranova INFN-LNF on behalf

of the OPERA Collaboration


The strength of the experimental evidence

Resides in the overall consistency of highly non-trivial tests both in the

solar and in the atmospheric sector: NC/CC (SNO), matter vs non matter

dominated oscillations (Solar+Kamland), natural vs artificial sources

(SK+K2K+MINOS)

Nobody has observed unambiguously the appearance of new flavours

You can’t do it at the solar scale (E too small to produce muons)

At the atmospheric scale oscillations are very likely

P(ν μ

→ν τ

) ≈ cos 4 ϑ 13

sin 2 2ϑ 23

sin 2 [1.27 Δm 2 23 L(km)/E(GeV)]

Hence, you must be able to identify unambiguously τ leptons

The CNGS experiments have been designed for it


Cern Neutrinos to Gran Sasso (CNGS)

ν μ

CC / kton 2900

ν μ

NC / kton 875

< E > ν ( GeV ) 17

(ν e +

ν e

) / ν μ

0.85 %

ν μ

/ ν μ

2.1 %

ν τ

prompt negligible


First Horn delivered to

CERN – April 2004

First quadrupole

installed, ProtonJuly beam 2005 tunnel

Feb. 2005

Transfer line

Target


The OPERA experimental design

ν

1 mm

τ

• Target based on the Emulsion Cloud Chamber (ECC) concept

• 56 1mm Pb sheets and 57 (300 μm thick) emulsion films

• At the same time capable of large mass (1.8 kton) and high

spatial resolution (


Conceptual design

Target:

• Lead/emulsions bricks

alternated to scintillator strips

SM1

SM2

• emulsion tracking resolution:

δx< 1μm, δθ


Automatic Emulsion Scanning

Off-line Data Taking

~ 30 bricks will be daily extracted from target and analyzed using high-speed

automatic systems

Several labs distributed in Europe and Japan

European Scanning System

S-UTS (Japan)

High speed

CCD Camera (3 kHz)

Piezo-controlled

objective lens

Synchronization of

objective lens and stage

scanning speed ~ 20 cm 2 / h

Customized commercial optics and

mechanics + asynchronous DAQ software

Constant speed stage

Hard-coded algorithms


Field of view

16 tomographic images

200 μm

47μm emulsion sheet

3D reconstruction of particle tracks

2D Image

processing

Passing-through

tracks rejection

Track segments found

in 8 consecutive plates

Vertex

reconstruction

Momentum measurement by Multiple Scattering

dE/dx for π/µ separation at low energy

Electron identification and energy measurement


ν μ → ν τ search

Several τ decay channels exploited

τ → eν τ ν e “ long decays ”

τ → μν τ ν μ “ long decays ”

τ → h “ long decays ”

ε.BR = 2.8-3.5%

τ→ eν τ ν e “ short decays ”

τ → μν τ ν μ “ short decays ”

ε.BR = 0.7-1%

Fiducial volume

kink angle

θ kink > 20

mrad

impact

parameter

I.P. > 5 to

20 μm

Recently added: τ → 3h long and short decays

Main backgrounds:

• charm decays

• large angle μ scattering

• hadron reinteractions


The Δm 2 23 saga

Atmospheric exps:

Frejus

Kamiokande

IMB

Super-K

Macro

Δm 2 (10 -3 eV 2 )

1990

1994

1997

1998

1999

2000

2001

2003

90% allowed regions

for different exps as a

function of the time

Nota Bene

P osc goes like (Δm 2 ) 2

From ’94 to ’03 it

decreased by a factor

of 100 !!

YEAR

It made our experiment challenging:

• Maximise efficiency

• Precise control of contamination to preserve the outstanding S/N

of OPERA

• Possibly, increase of intensity for CNGS


τ decay

channels

Search for ν μ →ν τ oscillation:

expected number of events

Δm 2 = 2.4 x 10 -

3

eV 2

Signal

Δm 2 = 3.0 x 10 -3

eV 2

Background

τ→µ

3.6

5.6

0.23

τ→e

4.3

6.7

0.23

τ→h

3.8

5.9

0.32

τ→3h

1.1

1.7

0.22

ALL

12.8

19.9 1.0

Main background sources:

- charm production and decays

- hadron re-interactions in lead

- large-angle muon scattering in lead

full mixing, 5 years run @ 4.5x10 19 pot / year


OPERA sensitivity to θ 13

Simultaneous fit of E e , missing p T and E vis distributions

10% syst. in ν e contamination

Preliminary

2.5x10 -3 eV 2 0.06

M.Komatsu, P.Migliozzi, F.Terranova J.Phys. G29 (2003) 443.

Limits at 90% CL for

Δm 2 = 2.5x10 -3 eV 2 full mixing

sin 2 2θ 13 θ 13

CHOOZ


Brick assembling and

installation in progress


Commissioning July 2007 and… August 18th - 30th, first Low Intensity CNGS RUN


1 st CNGS run: august ‘06

10.5 μs 10.5 μs

50 ms

1.7x10 13 pot/extraction (70% nom.)

SPS cycle 16.8 sec

1 st Extraction

2 nd Extraction

Unix time (ns)

Total: 7.6 E17 pot

Ext1: 3.81 E17 pot

Ext2: 3.79 E17 pot

Fri 18 Aug. 2006 13:40

2 days MD + problems

on Friday 25

Unix time (ns)

MD Monday + CNGS

smoke detection

system problem

CNGS eff. ~ 65%

Wed 30 Aug. 2006 05:00


Event Time Structure

OPERA

OPERA

• Beam events are selected

correlating events GPS time

information with CERN beam

spill time

• 319 events on time selected

Cosmic ray background

Extraction length = 10.5 μsec


Beam Direction

OPERA

Zenith angle of

muon track

y

θ y

>0

θ y


νCC in Target Tracker

• OPERA collect 319 beam events

• ~3/4 external events (rock)

• ~1/4 internal (CC + NC)

νNC in Target Tarcker

• Detector life time ~ 95%

R Acquafredda et al., New J. Phys. 8 (2006) 303

• lower limit due to CERN db problem

νCC in Magnet

νCC in rock (rock muon)


Target Tracker to Brick

connection

Changeabl

e

Muon

sheets

track

in emulsion

τ

1 st emulsion

sheet

Brick

Target Tracker

• Muon tracks predicted by target

One target wall tracker partially found instrumented

the CS doublets.

with dummy bricks • Angular with difference real Changeable between

Sheet (CS) doublet prediction to test and the found Target track


Next year CNGS run: draft

SPS physics run:

Start: 26/5/2007

End: 7/11/2007

• 141 days of physics runs, excluding

machine development.

• completion of CNGS commissioning at

the beginning of the physics run: OCT 06

run canceled due to a water leak in the

second CNGS horn

• No high intensity beam (2.4·10 13

pot/extraction) until OPERA has reached 75%

of the target mass

• Integrated protons in the 2-3·10 19 pot range


• A very special year for CNGS and OPERA!!

• Startup of CNGS was successful

• Performance of the OPERA electronic detectors are eccellent: the

electronic detectors took data almost continuously (95% live time)

and with the expected tracking performances

• More than 300 in-spill events have been recorded with a clear time

distribution. Flux and kinematic distributions OK.

• Electronic detectors to changeable sheet connection tested with

success

• Problems with the 2° CNGS horn (“reflector”):

no run in Oct 2006

• Brick installation and production in progress.

• Physics will come in 2007…

Conclusions

More details in R Acquafredda et al., New J. Phys. 8 (2006) 303

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