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京都大学 / 新制・課程博士 / 博士(理学) / 甲第23001号 / 理博第4678号 / 新制||理||1671(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 市川 温子, 准教授 成木 恵 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24406号 / 理博第4905号 / 新制||理||1701(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 WENDELL Roger, 教授 永江 知文 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

L'expérience OPERA (Oscillation Project with Emulsion t-Racking Apparatus) se propose de vérifier les résultats de Super-Kamiokande, tout en détectant l'apparition de neutrino tau dans un faisceau originellement "pur" en neutrino muonique, révélée par la topologie caractéristique de la désintégration du tau. La cible d'OPERA est constituée de murs de briques qui sont une alternance de feuilles de plomb et d'émulsions. Les émulsions sont des trajectographes de grande précision (~1 micron) qui vont être utilisés en masse lors de l'expérience et leur analyse nécessite un système de scan automatisé dédié. Tout d'abord, cette thèse a consisté en la participation à la mise en place du premier laboratoire de scan en France. La précision obtenue est conforme aux exigences de l'expérience et la rapidité demandée sera atteinte dans quelques mois. Ensuite, la séparation des pions et des muons à basse énergie a étudiée. Les premiers résultats, montrant la possibilité d'une telle séparation, ont été exposés. Enfin, un programme de reconstruction de ces particules en fin de parcours a été développé et testé, tenant compte des performances de scan auparavant étudiées.

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.

The aim of the OPERA experiment is to verify the neutrino oscillation, directly measuring the appearance of from an initially pure beam produced at CERN. For this purpose OPERA detector is located underground Gran Sasso Laboratory(LNGS) 730 km away from CERN. The detector structure designed to be a hybrid system consisting of emulsion targets and electronic detectors. Total area of the emulsion targets in the OPERA detector is around 110000 m2 which needs fast and reliable automatic scanning systems. For this purpose, two dierent automatic scanning systems were developed in Japan and Europe. For now there are 12 scanning laboratories dedicated to the OPERA Experiment. The Emulsion Scanning Laboratory in the Physics department of METU is one of the scanning laboratories for the OPERA Experiment. The automatic scanning system in METU is European type which is using commercial hardware for easy construction and maintain. Also the laboratory has a unique feature in terms of experimental high energy physics laboratories. The emulsion scan- ning laboratory in METU is the

OPERA stands for Oscillation Project with Emulsion t-Racking Apparatus. The main goal of the OPERA experiment is to search for tau neutrino appearance in almost pure muon neutrino beam. The detector is located at Gran Sasso, 730 km away from the neutrino source, at CERN. In this thesis, the reconstruction efficiency and purity of neutrino interactions in the OPERA target have been studied by using Monte Carlo simulation. The efficiency of primary vertex reconstruction for muon neutrino Charge Current (CC) events is estimated as 83.2 percent. The main source of inefficiency is due to Quasi-elastic like topologies in which only one track is reconstructed. The purity of primary vertex tracks is found to be 99 percent. On the other hand, the reconstruction efficiency for muon neutrino CC charm events is estimated to be 90.2 percent, while the purity of the primary tracks is 67 percent. The low purity is due the fact that the secondary vertex tracks are wrongly assigned in the primary vertex. This spoils the purity.

The OPERA experiment was designed to search for nu-mu to nu-tau oscillations through the observation of nu-tau charged-current interactions in the OPERA target. This search requires a massive detector and very high spatial accuracy. Both requirements are ful