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Université Paris Sud - Paris XI (09/12/2011), Achille Stocchi (Dir.)
A detector for charged particle identification in the forward region of SuperB
Leonid Burmistrov1
SuperB Collaboration(s)

In this thesis, we present the conception, the performances studies and the first tests in the Cosmic Muon Telescope situated at SLAC of a new detector for the particle identification in the forward region of the SuperB detector.This detector is based on time-of-flight (TOF) technique. To identify the particles with momentum up to 3 GeV/c and flight base around two meters we need a TOF detector able to measure the time with a precision of about 30 ps. To achieve this goal we have conceived a device producing Cherenkov light in a fused silica (quartz) radiator, by a charged particle, which then detected with very fast photodetectors and dedicated ultrafast electronics. We call it, the DIRC-like TOF detector.For what concern the photodetectors, the HAMAMATSU SL-10 MCP-PMT has been characterized at LAL test bunch and the time resolution of about 37 ps has been measured. The new 16-channel USB WaveCatcher electronics developed by LAL (CNRS/IN2P3) and CEA/IRFU has shown to have a jitter of less than 10 ps. The geometry of the quartz detector has been then carefully studied with Geant4 simulation. Which shows that the best detector geometry allow to reach the time resolution of about 90 ps per photoelectron with at least 10 photoelectrons detected, giving in average the desired 30 ps total time resolution.We have constructed a prototype of such device, using the quartz bars available from the Babar experiment, and we have installed it, in the SLAC Cosmic Ray Telescope. A time resolution of about 70 ps per photoelectron was obtained, in agreement with simulation.This proof-of-principle has convinced the SuperB Collaboration to adopt such a device as the baseline for the SuperB particle identification detector in the forward region. The delicate point which is still opened is the resistance of this detector to the machine background.In this thesis we also present preliminary studies of different types of background and their effect on the performances of the DIRC-like TOF detector. Radiative Bhabha process is by far the dominant source of background. The rate of the background photoelectrons caused mainly by the gammas with energy around 1.4 MeV is estimated to be ~480 kHz/cm^2 which corresponds to 2 C/cm^2 of integrated anode charge in 5 years. The neutron flux thought the DIRC-like TOF front end electronics is ~10^11/cm^2/year. These preliminary results are reassuring.
1 :  LAL - Laboratoire de l'Accélérateur Linéaire
Physique/Matière Condensée/Autre

Physique/Physique/Instrumentations et Détecteurs
Čerenkov – Détecteurs de – Identification des particules
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