The OPERA experiment - Infn

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The OPERA experiment - Infn

The OPERA experiment

Alessandra Pastore

Bari University & INFN

on behalf of the OPERA Collaboration

37 INSTITUTIONS ~ 160 PHYSICISTS

Technion Haifa

IPNL, IPHC, LAPP

Hamburg, Münster, Rostock

Bern, ETH Zurich

IRB Zagreb

Jinju

L’Aquila, Bari, Bologna, Napoli, Padova, Sofia

Roma, Salerno, LNF, LNGS

JINR,INR-RAS,ITEP,

MIAMI 2008 Aichi, Toho, Kobe, Nagoya,Utsunomiya

A. Pastore

LPI-RAS,SINP-MSU,Obninsk

1

METU Ankara

IHE Bruxelles


Outline

• Physics motivation

• Strategy and physics potential of the

experiment

The OPERA detector @ LNGS

• 2008: the first year of data taking

• Conclusions

MIAMI 2008 A. Pastore 2


OPERA Physics motivation

1998 SK atmospheric neutrino anomaly:

deficit of ν μ ( and not ν e ) with

zenith angle dependence: OSCILLATION !!!

L

CHOOZ: final

flavour not ν e

...

1999 CNGS beam design

2000 DONUT “sees”

the ν τ

in the nuclear

emulsions

MIAMI 2008 A. Pastore 3

2000 OPERA proposal


The Oscillation Project with Emulsion

tRacking Apparatus

The OPERA experiment is part of the CNGS project

(Cern Neutrino to Gran Sasso) developped to provide

an unambiguous evidence for ν μ

→ν τ

oscillation in the

region of atmospheric neutrinos.

OPERA is the only experiment looking for ν τ

appearance in a pure ν μ

beam produced at CERN

OPERA/CNGS1:

Hybrid set-up

(nuclear emulsions + electronic detectors)

MIAMI 2008 A. Pastore 4


OPERA/CNGS1: the beam

P+C (interactions) π + , Κ + (decay in flight) μ + + ν μ

~ 1 km, 2.5 m

vacuum

400 GeV diameter: 80cm & 115 cm K + , π +

current: 150kA & 180 kA

20–50 GeV

The CNGS is a conventional neutrino beam: 400 GeV/c protons from the

CERN SPS hit a graphite target producing pions and kaons which decay in

flight and produce neutrinos

MIAMI 2008 A. Pastore 5


OPERA/CNGS1: the beam

Pr(ν μ

ν τ

) & σ ν(τ)CC

(Ε) convolution

maximized high E beam

(“appearance”- optimized)

CERN

L = 732 km

LNGS

MIAMI 2008 6


OPERA: expected signal and backgrounds

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

main background sources:

- charm production and decays

- hadron re-interactions in lead

- large-angle muon scattering in lead

MIAMI 2008 7


ν τ appearance :

experimental signature in OPERA

goal: detect ν τ

CC interactions through direct observation of τ decays

Topology selection kink signature

ν τ

τ

~ 0.6

mm

ν μ ↔ ντ → τ - + X

μ − ν τ ν μ (17 %)

h - ν τ n(π ο ) (50 %)

e - ν τ ν e (18 %)

π + π − π − ν τ

n(π 0 ) (14 %)

“kink”

topologies

OPERA detector requirements:

‣ Large mass (1.35 Kton)

‣ High resolution

signal selection

background rejection

@ 4.5·10 19 p.o.t./year, 200 days/year

for OPERA (~1.35 Kton) means:

~ (19600 ν μ CC + 5900 ν μ NC)

MIAMI 2008 8


The OPERA brick

target basic component :

8.3 Kg

brick:

compact and modular structure:

57 emulsions films sandweeched

between 1mm Pb sheets

ν

1 mm

τ

Pb

Emulsion layers

~ 150000 bricks in the OPERA target (~ 1.35 kton)

each emulsion film:

What the brick cannot do:

2 emulsion layers

(44 μm thick)

poured on a

200 μm plastic base

On each brick: 1 CS doublet

10.2cm

12.5cm

• trigger for a neutrino

interaction

• muon identification and

momentum/charge

measurement

two double refreshed emulsion

films,vacuum MIAMI 2008packed and glued onto the A. Pastore 9

downstream brick face

need for an hybrid detector


The OPERA detector@LNGS

Surface INFN laboratory 980 m

the underground lab is at about

the same altitude

Laboratori Nazionali del Gran Sasso (Italy)

•1400 m rock overburden

• cosmic µ reduction ~ 10 6 (1μ /m 2 /h)

low radioactivity rock

OPERA

MIAMI 2008 A. Pastore 10


The OPERA detector@LNGS

SM1

SM2

Veto (RPC)

Target + Target Tracker (6.7m) 2

High precision tracker

● 6 4-fold layers of

drift tubes

Dipole magnet

● 1.53 T

● 22 x 2 XY planes of RPC

muon spectrometer (8×10 m 2 )

● target/SM: 77500 bricks

(Pb – nuclear emulsions)

in 29 walls

Mass/SM 0.67 kt

● Target tracker : 31 doublets XY

(256 plastic scintillator strip + WLS

MIAMI 2008 A. Pastore fibres+ multi-anodes PMT) for brick 11

selection and calorimetry


The OPERA target

● Micro-metric space resolution (emulsion) + target mass (lead)

● Compact and modular structure

Target brick wall:

• light structure (0.6% target mass)

• strong enough to handle 30tons/plane

Target tracker:

• 7000 m² scintillator strips

• 1000 MAPMT (64 #)

wall

52 x 51 bricks

TT

7m

Total target mass : ~ 1.35 Kton

MIAMI 2008 A. Pastore 12

(~150000 bricks, 9M emulsion films)


ick production and processing:

BAM and BMS

Brick Assembly Machine:

robots piling up bricks

at a rate of ∼ 700 bricks/day in a dark room

Brick Manipulator System:

robot for brick insertion (target filling)

and removal (during run)

BMS

Spatial precision o(0.1 mm)

on ranges o(10 m) using

digital camera vision

Tagged bricks will be extracted every

day quasi online experiment

MIAMI 2008 A. Pastore 13


ν τ hunting: the OPERA way...

Spectrometer

On-line analysis of electronic data

brick finding algorithm

ν τ

μ

selection of the interaction

brick provided by time correlation

of electronic detectors

Target Tracker

+ Brick Walls

υ

0

max

p.h.

Electronic detectors goal: Brick finding, muon ID, charge and p

Emulsions’ analysis goal: Vertex, decay kink, e/γ ID, momentum measurement

MIAMI 2008 A. Pastore 14

by Compton multiple scattering, kinematics


ν τ hunting: the OPERA way...

- once the selected brick is removed from the target, CS doublet

is scanned in dedicated OPERA Scanning Stations (located at

LNGS and in Japan)

- if any track originating from the interaction is detected in the CS,

the brick is exposed to cosmic rays (alignment)

- the brick is depacked and the emulsions are developed

- the brick is sent to scanning stations/labs

- Event location

- Decay search

- Particle ID and kinematics

- Event classification

MIAMI 2008 A. Pastore 15


OPERA emulsions’ data taking:

automatic microscopes

20 ~ 30 bricks will be daily extracted from the target

and analyzed using high-speed automated systems

European Scanning System

S-UTS (Japan)

Common Data Base for data sharing/publication

Piezo-controlled

objective lens

High speed

(‏kHz CCD Camera (3

Customized commercial optics and

mechanics + asynchronous DAQ

Synchronization of

software modular, de-centralized,

MIAMI 2008 A. Pastore

objective lens and (constant speed) stage

16

approach

Hard-coded algorithms, custom electronics


Scanning OPERA emulsions ...

1 plastic base

(200 μm)

2 emulsion

sheets

(45 μm)

Field of view

300 micron

16 tomographic images

2D Image

processing

1 lead sheet

(1 mm)

3D reconstruction of particle tracks

Spatial resolution < 1 μm

Angular resolution < 2 mrad

MIAMI 2008 A. Pastore 17


event reconstruction chain ...

track search in the CS doublet

following the electronic detectors predictions

scan-back efficiency

93.1%

scan-back

tracks followed backward

film by film inside a small area

(~ 300x400 μm 2 )

volume scan

a greater area scanning

(~ 25 mm 2 ) around any existing

track’s stop

vertex

reconstruction

angular residuals between

base-tracks and fitted volume tracks

(vertical tracks)

position residuals between

base-tracks and fitted volume tracks

MIAMI 2008 A. Pastore 18


2008 run: CNGS integrated intensity

Nominal intensity :

4.5 10 19 pot /yr

(1yr=200 days)

pot

1.782 E 19 pot

3/11 8:00

1.782 E 19 pot

Horns filters

19-20/10

18KV cable accident

25/7

6-8/10 MD

Beam loss,

vacuum accident

27/6-2/7

Wed 18/6

17:00

Start of

commissionin

g at low

intensity

10/7-18/7 Earth

fault on the PS

magnet

Long MD stop + MTE kicker

problem

7/7 6:00 – 10/7 12:00

Unix Time

Horn + PS vacuum

Week 1/9

PS septum + Long MD

8-14/8

CNGS quadrupole

14-17/9

19


Run 2008

Started since June 18th, end on November 3rd

Beam performance for the 2008 run:

Efficiency

Intensity (p.o.t. / extraction)

60% ( expected 80%)

2x10 13

Integrated p.o.t.

1.78x10 19 pot

(80% of the expectations)

Detected interactions:

Recorded on time event

Candidate ν Interaction

(In the target)

10058

1690

(MC expected 1700)

MIAMI 2008 A. Pastore 20


event reconstruction chain in 2008 run...

TT-CSd agreement: CC interactions

position residuals (x proj.) between TT predicted

tracks and tracks reconstructed in CSd

position residuals (y proj.) between TT predicted

tracks and tracks reconstructed in CSd

σ~7 mm σ~8 mm

angular residuals (x proj.) between TT predicted

tracks and tracks reconstructed in CSd

angular residuals (y proj.) between TT predicted

tracks and tracks reconstructed in CSd

ΔPredY[mm]

σ~21 mrad

σ~21 mrad

MIAMI 2008 A. Pastore 21


event reconstruction chain in 2008 run...

TT-CSd agreement: NC interactions

position residuals (x and y proj.) between the centroid predicted by electronic detectors and the nearest track

(wrt the centroid) reconstructed in CSd

σ~9 mm

σ~9 mm

MIAMI 2008 A. Pastore 22


event reconstruction chain in 2008 run...

CSd – brick agreement

position residuals between CSd tracks and

tracks reconstructed in the corresponding brick

80 µm

angular residuals between CSd tracks and tracks

reconstructed in the corresponding brick

8 mrad

MIAMI 2008 A. Pastore 23


Vertex location results

obtained on a subsample of measured events

NC

CC

Bricks received in the labs

48

200

Scanning started

43

178

CS to brick connected

40

172

Vertices reconstructed

29

145

Vertices in the dead material

1

5

Track passing through the

assigned brick

3

8

@12/11/2008

CS to brick connection success:

93% (NC) 97% (CC)

Iterative process (CS and brick scan) for either not connected or not located events


Vertex characterization

Multiplicity at interaction vertex

Tracks-vertex impact parameter distribution

MIAMI 2008 A. Pastore 25


And now let's “open the box” ... !

A selection of neutrino

vertices reconstructed in

the emulsion detectors ….

MIAMI 2008 A. Pastore 26


CC interaction

Event 231059735 - Brick 107936

8 m

19 m

OPERA level

MIAMI 2008 A. Pastore 27


NC interaction

Event 234302273 – Brick 1023488

lead plate between

films 42 and 43

Nr of tracks: 6

MIAMI 2008 A. Pastore 28


An interesting CC interaction ....

53

p l a t e

54

55

56

57

csd

ΔΦ ~ 150°

~ back to back

favour charm

interpretation

Charged parent path

length ~ 1150 μm

4 prong 1ry

~30 μm in Pb

quite downstream:

4-5 plates available

(+2CS)

3 prong

secondary

~200 μm in

Pb

analysis on-going...

μ

MIAMI 2008

μ

(prompt)

A. Pastore 29


Conclusions

The OPERA detector and its infrastructure successfully

operated during 2008 CNGS run

• Partial recovery of the beam after a rather problematic start:

1.78x10 19 instead of 2.2x10 19 p.o.t.

• About 1700 events in the bricks: sample to fine tune OPERA

analysis and to estimate efficiencies and background

• In 2009 CNGS run the integrated intensity is expected to reach

3.5x10 19 p.o.t. :

for OPERA this means < 3 tau events in the 2008-2009 data

MIAMI 2008 A. Pastore 30

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