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Do background to neutrino oscillations in the opera experiment

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2009
Tufanlı, Serhan
The OPERA experiment is designed to search for nu-tau appearance in almost pure CERN-SPS nu-mu beam. The OPERA detector is placed in the Gran Sasso underground laboratory which is 730 km away from CERN. It is a hybrid set-up which combines a lead/emulsion target with various electronic detectors. The detector is composed of two super modules(SM) which contains about 150,000 ECC bricks. Each of the brick is obtained by stacking 56 lead plates with 57 emulsion films. Behind the each brick, an emulsion film doublet, called Changeable Sheet (CS) is attached in order to confirm tracks produced in neutrino interactions. The CS requires very low background track density in order to ensure the expected performance in the experiment. The background tracks in CS can be erased by a special treatment called as refreshing. A refreshing facility was constructed in the LNGS laboratory. The METU group has participated in the construction of the facility and the production of the CS films from the beginning. The main steps of emulsion refreshing and the test results on emulsion quality after the refreshing will be discussed. A Monte Carlo simulation is performed in order to estimate background to nu-mu to nu-tau oscillation due to D0 production and decay in the ECC brick. It is found that this background is significant for the short decay path topology of the tau lepton.