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TEST BEAM EXPERIMENT
OPERETTE
C. HERITIER on behalf of operette working group
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• OPERETTE
• WHY?
• The main aim of Operette is to prepare OPERA
  for what concerns the scanning of emulsion films
  with neutrino events.
• to check and improve on vertex finding
  efficiency.
• to check the validity of the brick finding
  efficiency
• to check the back scattering contribution.
• USING FREE NEUTRINO BEAM

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The beam layout

• 400 GeV p SPS cycle16.8s/Slow spill 5.2 s
• p(K) beam 9.6 mrad upwards/0.3 mrad spread
• Muons at EHN2 2x108 /1013 pot(cycle)
• Neutrinos 2x109/cycle

• Narrow radial distribution gt small size detector
• Strong correlation between neutrino energy and
  radial position (CC/NC)

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Predicted energy from radius vs true energy
Mean Energy vs Radius
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shielding
beam
1 m
emulsion bricks
TT
dummy bricks
SFT
RPC
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SFT
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Neutrinos
1020 m
On-axis
GeV
4 events/brick/month
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• Physics Strategy
• Run during 1-2 months with bricks kept in place
• Events triggered are recorded from both TT and
  SFT
• SFT will be used to estimate the brick finding
  efficiency
• based on TT information
• (information from SFT seems enough to locate, at
  very high efficiency, the brick)
• SFT will be used to estimate the back-scattering
  
• After the run ? develop and scan all the bricks
• ? compare with TT, SFT

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BRICK FINDING EFFICIENCY WITH SFT

• We are developping an algorithm using
  information
• of SFT detectors to find the brick. This
  algorithm uses a
• barycentric method (possible reconstruction of
  particles
• direction using the 2 doublets of each station).
• For the Charged Current events, we have a
  resolution
• about 95 and for the Neutral Current events, 92.

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BACKGROUND

• muons produced by neutrino interactions in
• the earth in front of the detector. The first two
  
• RPC stations and the first plane of scintillators
  
• allow to improve the rejection efficiency of
• those muons.
• cosmics some preliminary results concerning
  this point (Trigger study).

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Rock Muons Produced by neutrino interaction in
the rock
GeV
6 105 muons/month
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• TRIGGER
• Rock muons
• Using the veto system (2 RPC stations first TT)
• 6.105 muons/month ? 2 muons escaping
  detection for 1 month.
• Cosmics
• A complete trigger scheme is under study using
  TT RPC informations (at present only the TT
  information is used)
• Furthermore the use of the SFT requires a fast
  hard trigger (due to the acquisition rate of the
  CCD reading out the SFT 30 fps)

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COSMICS

• The experimental set-up was simulated in the
  Geant3 code.
• We used the same neutrino events generator as
  for OPERA to produce 10000 ??CC events with the
  expected energy spectrum given by the halo code.
• For the generation of cosmics muons, we use a
  generator provided by M. Sioli.
• data1 1 minute of cosmics flux in the energy
  range 0.2-1000 GeV and for zenith angles greater
  than 70 degrees (10 h CPU time)
• data2 10 seconds of cosmics flux in the
  energy range 0.2-10 GeV but for all zenith angles
  (more than 20 h CPU time)

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?
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Energy spectrum of cosmics muons.
data1
data2
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Energy spectrum of neutrino events generated(CC)
? from ?? interaction
The interaction vertex are distributed randomly
inside the emulsion bricks.
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Number of scintillator planes per event
cosmics
neutrinos
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Number of strips per event
muons
neutrinos
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Number of photoelectrons per event
cosmics
neutrinos
The digitization takes into acount the response
of PM.
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Number of RPC stations per event
Station 1
Station 2
Station 3
Station 4
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FIRST RESULTS

• Using a cut at 25 strips per event
• we have 98 of rejection for cosmics and 90 of
• efficiency for neutrino events.
• BUT we can improve by
• using information from RPC stations
  in front of the detector
• using the information on the number of
  photoelectrons.

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CONCLUSION

• Operette can be a real test for different
  sub-detectors
• Emulsion, Scintillators, RPC, Electronics ,
  Scanning.
• Acquisition (electronics, scanning) can be
  tested and
• strategies can be decided accordingly.
• Many studies are done and an OPERA note will be
  soon
• available
• Expected time to start in 2004

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• Installation Strategy
• TT planes with endcaps and electronic readout
• should be assembled in one lab.
• Bricks should be prepared and put in their walls
  
• at CERN (aleph pit?)
• The set-up should then be completed quickly
• on the detector place before the run
• It is possible to run one month with only fake
  bricks to test electonics

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• Needs List
• Mechanical structure 2 men during 1
  month
• TT planes construction 3 men during 1
  month
• Bricks 4 man
  during 15 days
• installation 2-4 man
  during 1 week
• Shift 2 men
  for one month
• developement 1-2 men for
  one month

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SFTEmul. Bricks 56.3 K
PMT (22) OPERA
Scint. Strips 800X1 m 2 K
Fibers 800X3 m 4.8 K
Scint. Endcaps 11 K
Scint. Readout OPERA?
RPC Readout 3 K
Lead OPERA
Mechanical structure 2 K
Infrastructure 100 K
TOTAL 180 K