OPERETTE TEST BEAM EXPERIMENT : C. HERITIER on behalf of operette working group

USING FREE NEUTRINO BEAM 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

The beam layout 400 GeV p SPS cycle=16.8s/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 => small size detector Strong correlation between neutrino energy and radial position (CC/NC)

Predicted energy from radius vs true energy Mean Energy vs Radius

shielding beam # 1 m emulsion bricks TT dummy bricks SFT RPC

SFT

Neutrinos On-axis 1020 m GeV 4 events/brick/month

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

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%.

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).

Produced by neutrino interaction in the rock Rock Muons Produced by neutrino interaction in the rock GeV 6 105 muons/month

TRIGGER Rock muons: Cosmics : 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)

The experimental set-up was simulated in the Geant3 code. 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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Energy spectrum of cosmics muons. data1 data2

Energy spectrum of neutrino events generated(CC)  from  interaction The interaction vertex are distributed randomly inside the emulsion bricks.

Number of scintillator planes per event cosmics neutrinos

Number of strips per event muons neutrinos

Number of photoelectrons per event cosmics neutrinos The digitization takes into acount the response of PM.

Number of RPC stations per event neutrinos cosmics Station 1 Station 2 Station 3 Station 4

BUT we can improve by: 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.

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

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

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

SFT+Emul. 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 Mechanical structure 2 K € Infrastructure 100 K € TOTAL 180 K €