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Caractérisation des différentes options du trajectographe du détecteur OPERA

Abstract : Neutrinos were postulated by Pauli during the thirties. These spin-half and massless particles helped to solve the beta desintegration problems. Their study started in the fifties and work is still going on nowadays. This lengthy study is due to the difficulty to detect neutrinos and also to a "strange" phenomenon : we always detect less neutrinos than expected for solar and atmospheric neutrinos. This phenomenon can be explained by oscillation between massive neutrino states.
The OPERA project is intended to directly prove this oscillation. In this aim, a nu_mu beam is produced at CERN and pointed to Gran-Sasso (Italy), 732 km away. The detector is optimised to reveal the neutrino tau coming from nu_mu --> nu_tau oscillation. This detector of 30 meters long with 2 000 tonnes of target will be built with more than 200 000 bricks of lead and emulsion. Taus are observed after scanning of the emulsions. The bricks must be localised into the wall and this localisation is possible with a tracker located of downstream each target wall.
The present work was devoted to the determination of the best tracker for OPERA. Three options were studied and a tracker made of plastic scintillator slabs has been choosen. It allows a wall finding efficiency around 80% and a brick finding efficiency around 80%. As photo detector, we have studied HPD with an auto triggerable readout. HPD's have displayed an excellent resolution, a cross talk lower than 2% and an uniformity higher than 98%. A DAQ based on Ethernet was proposed and accepted by the collaboration. In this option, each photo detector is a node of the network and can be accessed by a web browser. A prototype with plastic scintillator, HPD with an auto triggerable readout and a DAQ based on Ethernet has been built and validated during beam tests.
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https://tel.archives-ouvertes.fr/tel-00001799
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Submitted on : Wednesday, October 9, 2002 - 8:03:19 AM
Last modification on : Tuesday, November 19, 2019 - 2:45:14 AM
Long-term archiving on: : Friday, April 2, 2010 - 6:30:38 PM

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  • HAL Id : tel-00001799, version 1

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Guillaume Moret. Caractérisation des différentes options du trajectographe du détecteur OPERA. Cosmologie et astrophysique extra-galactique [astro-ph.CO]. Université Claude Bernard - Lyon I, 2002. Français. ⟨tel-00001799⟩

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