# Recherche des oscillations de neutrinos par apparition du $\nu_\tau$ avec désintégration muonique du $\tau$ dans l'expérience OPERA

Abstract : The physics of neutrino oscillations plays a major role in the studies on that particle. The oscillations, based on a change of flavor state of a neutrino during its propagation, can explain the deficits observed on solar and atmospheric neutrinos and provide some interesting indications for physics beyond the Standard Model by studying the mixing angles and the hierarchy of neutrino mass. The OPERA experiment is the first experiment designed to observe the appearance of a$\ nu_\tau$ by the oscillation of the $\nu_\mu to\ nu_\tau$ in the CNGS beam from Cern to Gran Sasso. OPERA is a hybrid detector combining both the technique of a on time electronic detection and the technique of emulsion cloud chamber or ECC. The ECC detector is apassive detector (target) of 150 000 bricks, each one consisting of sheets of lead, used as target, alternating with nuclear photographic emulsions whose accuracy of track reconstruction is about one micron. The detector also includes two spectrometers with magnetized iron plates 5 cm thick alternating with RPC (resistive plate chamber) associated with six sets of drift tubes for the measurement of the charge and momentum of the muon. It includes also a Veto plane used for rejection of particles coming outside the target. This detector simultaneously allows a high spatial resolution and a large target mass which are two very conditions necessary for collecting charged current neutrino interactions from oscillated $\nu_\tau$ and observing the decay topology of tau. This thesis presents a study on tau decay in muonic channel. It has contributed to 1) the developpement of an algorithm for the selection of neutrino interactions in the target, 2) the studies on the muon identification in electronic detectors and the connection of its trace with those reconstructed in the emulsions, which represent a fundamental point both for the tau signal identification as the rejection of charmed background, 3) the development of a neural network to discriminate the signal from the charmed background regarless of the muon identification in electronic detectors, 4) the results of tau oscillation search in muonic channel decay, based on a 2008-2009 data, with the reevaluation of signal and background efficiencies.
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Submitted on : Wednesday, November 10, 2010 - 2:22:04 PM
Last modification on : Friday, September 10, 2021 - 1:50:07 PM
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• HAL Id : tel-00534753, version 1

### Citation

Ngoc Tiem Tran. Recherche des oscillations de neutrinos par apparition du $\nu_\tau$ avec désintégration muonique du $\tau$ dans l'expérience OPERA. Physique des Hautes Energies - Expérience [hep-ex]. Université Claude Bernard - Lyon I, 2010. Français. ⟨tel-00534753v1⟩

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