Oscillation Project with Emulsion tRacking Apparatus

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Oscillation Project with Emulsion tRacking
Apparatus
F. Juget Institut de Physique Université de
Neuchâtel
Neutrino-CH meeting, Neuchâtel June 21-22 2004
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• Physics motivation
• The OPERA detector
• Physics performance
• Conclusion

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Motivation
P(nm -gt nt ) cos4(q13) sin4(q23) sin2(2q23)
sin2(1.27 Dm2 L/E)
P(nm -gt nt ) cos4(q13) sin4(q23) sin2(2q23)
sin2(1.27 Dm2 L/E)

• Appareance search of nm lt-gt nt oscillations in
  the parameter region indicated by S-K for the
  atmospheric neutrino deficit.

Dm2 Dm223 Dm213
P(nm -gt ne ) sin2(q23) sin2(q13) sin2(1.27 Dm2
L/E)
gt Search for nt appearance in the CNGS nm
beam
Search for nm lt-gt ne put new constraints on
q13 Actual result (CHOOZ) sin2q13 lt 0.1
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OPERA/CNGS long base-line n project

• Seach for nt appearance at the Gran Sasso
  laboratory 732 km from CERN
• Beam optimized for nt appearance

6.7 1019 pot/year at CERN (shared mode)
For Dm2 2.4 10-3 and maximal mixing (sin22q
1) expect 23 nt CC/kton/year at Gran sasso
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Principle direct observation of t decay
topologies in nt cc events

• requires high resolution detector (mm) use
  photographic emulsions
• Needs large target mass alternate emulsion
  films with lead layer

206 336 bricks are needed ? target mass 1.8 ktons
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OPERA an hybrid detector

• What the brick cannot do
• trigger for a neutrino interaction
• muon identification, charge measurement
• gt need for an hybrid detector

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Spectrometer 1 May 17
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Last slab placing 19/5
(2.5 weeks in advance)
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May 25 Main structure start (drilling the floor
for fixing)
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Detector installation schedule

• Brick walls and Target Tracker walls for SM1
  Aug. 04 Jun 05
• Brick walls and Target Tracker walls for SM2
  Jul. 05 Mar 06
• Installation of Brick Manipulator System
  (BMS) Beginning 2005
• Start filling walls with bricks July 2005
• Ready to take data for 2006

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ntCC interaction identified looking at the t
decay gt search for a kink in consecutive
emulsions

• t decay channels
• t -gt m nm nt (17)
• t -gt e ne nt (18)
• t -gt h neutrals nt (49)
• 3h neutrals nt (15)

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Basic Ideas of Volume Scanning
Track processing takes further steps to reach
physics goals
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Automatic ScanningNagoya and Europe RD efforts
Bari, Bern, Bologna, Lyon, Münster, Napoli,
Neuchâtel, Roma, Salerno
Europe prototype (Neuchâtel exemple)
sq 2mrad sx 0.5mm
Dedicated hardware Hard coded algorithms
Commercial products Software algorithms
Routine ? 10cm2/hr Near future ? 20cm2/hr
S-UTS prototype at Nagoya
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Detected p interaction vertex
Brick exposed to p beam at 7 GeV/c

• Reconstruction
• Track M having beam slopes (0.056-0.004) and
  track D1 having slopes intersect in a kink
  topology

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Movie from E. Barbuto Salerno University
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Event reconstruction with emulsions

• High precision tracking (dx lt 1mm dq lt 1mrad)
• Kink decay topology
• Electron and g/p0 identification
• Energy measurement
• By Multiple Coulomb Scattering
• DP/P lt 0.2 after 5X0 up to 4 GeV

Topological and kinematical analysis event by
event
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Exploited t decay topologies
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Expected number of background events(5 years run
with 1.8 kton average target mass)
total
t?h
t?µ
t?e
t?3h
.573
.243
.017
.31
Charm background
.44
Large angle µ scattering
.174
.174
.313
.174
.139
Hadronic background
1.50
.42
.33
.31
Total per channel
.44

• Charm background
• Being revaluated using new CHORUS data cross
  section increased by 40
• pµ id by dE/dx would reduce this background by
  40
• ? tested at PSI (pure beam of p or µ stop)
• ? x 18 ! in the µ channel without a
  spectrometer
• Large angle µ scattering
• Upper limit from test _at_ CERN
• Calculations including nuclear form factors give
  a factor 5 less
• ? will be measured this autumn in X5 beam with
  Si detectors
• Hadronic background
• Estimates based on Fluka standalone 50
  uncertainty
• Extensive comparison of FLUKA with CHORUS data
  and GEANT4
• would reduce this uncertainty to 15

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Expected number of events
full mixing, 5 years run _at_ 6.7 x1019 pot / year
Channel Signal (Dm2 (eV2) )
e BR e. BR Background
1.9 10-3 2.4 10-3 3.0 10-3 e
3.7 6.1 9.2
19.4 0.175 3.4 0.31 m
3.1 4.8 7.6
16 0.175 2.8 0.33 h
3.2 5.1 7.8
5.8 0.50 2.9 0.42 3h
1.4 2.2 3.5
8.3 0.15 1.25 0.44 Total
11.4 18.2 28.1
49.5 1 10.35 1.5
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Probability of claiming a 4s discovery in 5 years
Opera with beam2
Opera with beam3
Opera, no beam upgrade but half background
Opera with beam4
SK 90 CL
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Electron identification andEnergy measurement

• Identification Method based on shower
  identification and on Multiple Coulomb Scattering
  of the track before showering
• e/p ratio is measured with Cerenkov and ECC (test
  beam)
• ECC 1.420.17 Cerenkov 1.460.11 at 2GeV
• ECC 0.410.05 Cerenkov 0.320.03 at 4GeV

• Energy Measured by counting the number of track
  segments into a cone along the electron track
• Multiple Coulomb Scattering before showering

_at_ a few GeV
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Electron identification efficiency

• e.m. and hadronic shower simulated in OPERA
  brick.
• No background simulation.
• Analysis based on neural network.
• Note that in the range 2?15 GeV and for particle
  crossing at least 2.5 X0, eID and pID is 99.
• OK for both t?e and ?µ??e searches

efficiencies for showers followed for 36 ECC
(6.4 X0)
To be tested in July _at_ DESY with a pure electron
beam at 1-6 GeV
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Expected signal and background for the nm ? ne
search

neCC beam
nmNC
nmCC
t?e
signal
Q13
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5.2
1.0
4.5
9.3
9º
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5.2
1.0
4.6
5.8
7º
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5.2
1.0
4.7
1.2
3º
0.082
7.0 10-4
0.34 10-4
0.032
0.31
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Statistique sur le bdf
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OPERA sensitivity to q13
Only 15 increase scanning because the event
location is already performed for nt search.
By fitting simultaneously the Ee, missing pT and
Evis distributions we got the sensitivity at 90
syst. on the ne contamination up to 10
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Activities of the swiss groups

• Bern and Neuchâtel are involved in OPERA
• Electronics
• Frontend Chip for the target tracker (Bern)
• Test and calibration of PMT for the Target
  Tracker (Bern)
• Scanning
• 1 microsope in each lab is already working
• A third one will be installed this year in Bern
• Development of an automatic emulsion changer
  (Bern)
• Simulation
• Geant4 simulation (Neuchâtel)

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Conclusions

• Detector construction and installation
• Installation of detector in progress
• Detector (and CNGS beam !) will be ready in 2006
• Scanning strategy still to be optimised

• Important Physics Program
• First evidence of nm-nt appearance in few years
  data taking
• In a five years run 18 signal (SK best fit) and
  1.5 background events
• Studies to improve efficiency and to reduce the
  background
• Significant measurement of q13

Very low background is the key issue