2008 European School of High-Energy Physics - Trest, Czech Republic - 19 August - 1st September

1. - n Decay “kink” nm 1.7m - Beam energy and contamination nm oscillation n t- 6.9m <E> 17 GeV nt (e+e)/ 0.73% 7 m  /  3.9% 7 m  prompt negligible Neutrino int. in TT 31 walls ~1 mm 2008 European School of High-Energy Physics - Trest,  Czech Republic - 19 August - 1st September Target Tracker Data Analysis In OPERA Experiment S. Dmitrievsky, S. Zemskova - JINR CNGS Beam OPERA Experiment The OPERA experiment is designed for direct observation of appearance in the CNGS long baseline beam (from CERN to Gran Sasso Laboratory) as a result of oscillation. OPERA exploits nuclear emulsions as very high resolution tracking devices for the direct detection of tau leptons produced in the charge current (CC) interaction of the with matter of the detector.  production threshold L/E ~ 43 km/GeV, not optimal for Posc Beam optimized to have the maximal number of Charged Current interactions (given the baseline L=730 km) OPERA subsidiary physics programme includes measurement of upper limit of at levelThe first CNGS neutrino test run took place in August 2006. OPERA detector : 2 identical super-modules (target, TT, Spectrometer) + veto system Target Tracker SM1 SM2 0.68 kton 0.68 kton m ID, charge, p Dp/p < 25% Wrong charge < 0.3% m ID, charge, p Plastic scintillator strips (AMCRYS-H, 6.7m x 2.6cm x 1cm) readout by Kuraray WLS fibres + Hamamatsu PMT’s (64 channels) • Target and Target Tracker (6.7m)2 • ● Target : 77500 bricks, 29 walls • ● Target tracker : 31 XY doublets of 256 scintillator strips + WLS fibres + multi-anodes PMT for • Brick selection • Calorimetry Veto plane (RPC) Target Tracker tasks: ● Trigger:  > 99% ● Brick finding :  7080% ● Initiate muon tagging High precision trackerInstrumented dipole magnet ● 6 4-fold layers of ● 1.53 T drift tubes ● 22 XY planes of RPC in both arms Muon spectrometer (8×10 m2) Detection of thentappearance signal Signal and background eventsnm -nt oscillation channel OPERA ECC Brick Lead plate(1mm) / Emulsion Film (OPERA film) Sandwich The challenge is to identifyntinteractions fromninteractions -decay channels Signal ÷ (m2)2 – Full mixing Background: Charm Hadron interaction Muon scattering 1 mm m2 = 2.5 x 10-3 eV2 m2 = 3.0 x 10-3 eV2 t 125mm n n Preliminary -  µ- 2.9 4.2 0.17 100mm Toplogy selection:  Kink signature Pb -  e- 3.5 5.0 0.17 Emulsion layers -  h- 3.1 4.4 0.24 -  3h 0.9 1.3 0.17 • Target:1800 tons, 5 years running • 30 000 neutrino interactions • ~150 ntinteractions • ~15 nt identified • < 1 event of background • Two conflicting requirements: • Large mass  low Xsection • High granularity  signal selection  background rejection ALL 10.4 15.0 0.76 5 years of data taking Nominal beam intensity 4.5*10^19 p.o.t./year 1.35 kton target mass (25% reduction w.r.t. proposal) 100mm Brick Finding 125mm Lead Plate Emuslion Film (OPERA Film) An essential issue in OPERA is finding of a target brick where the neutrino interaction took place. For this purpose the OpBrickFinder program was developed that performs the vertex brick identification using the informationfrom the target tracker and spectrometer. Our brick finding (BF)strategy includes the following steps: - event cleaning;- muon track identificatin and reconstruction;- hadron shower axis reconstruction; Alignment of TT with the help of muon tracks Alignment of the TT is essential for track reconstruction and the brick finding. Making use of straight cosmic muon tracks we clarify a geometrical position of the TT modules (the angles of rotation around of coordinate axes and displacement along the axes). We need to set local coordinate systems of modules to general system of coordinates of the experiment. - the most probable vertex walldetermination: Autumn 2007 CNGS Commissioning and Physics RUN For a vertex wall determination we use a multilayer perceptron (MLP) with standard back propagation training algorithm. 3 weeks of CNGS commissioning run + 3 weeks of physics run following June CERN SPSC recommendation . • If intensity as in August 2006 : 1.7 1013 pot/extraction (70% nominal) • If extraction scheme as in November 2006: 3 double fast extraction per 36 s SPS cycle • If typical 70 % efficiency of the machines complex • If target filling programme as scheduled Output variables of the neural network are probabilities of each wall to be a vertex wall. The wall finding efficiency achieved so far is ~85% for events - localization of the most probobal vertex bricks: After the vertex wall is selected by the NN, we use its position, a muon track, and/or a shower axis parameters to determine x-y coordinates of the vertex brick in the wall. Expected BF Efficiency: 1 brick extraction: ~70% 2 bricks extraction: ~85% 3 bricks extraction: ~90% We can see summary difference between experimental points and calculated tracks before alignment and after 3 iteration on these pictures.