Fiabilite à long terme des détecteurs gazeux à micropistes et de leur électronique de lecture dans les conditions de fonctionnement du LHC. Etude de la reconstruction des traces d'électrons dans le trajectographe du détecteur CMS.

Abstract : The CMS (Compact Muon Solenoid) experiment foresaw the use of MSGCs (MicroStrip Gas Chambers) on a surface of about 200 m2 in its inner tracker. The condition of exploitation (luminosity = 10^34 cm-2.s-1) has led to a thorough study of the radiation hardness and long term stability of the MSGCs. For that purpose, the CMS Tracker group of Lyon has proposed and evaluated a variant of MSGC : the SGC (Small Gap Chambers). In order to study the radiation hardness of SGCs, several tests have been done with a pion beam of 350 MeV at the Paul Scherrer Institut in Zurich. Initially performed with small size chambers (5 cm x 2.5 cm), the measured spark rate and the extrapolation to 500 LHC equivalent days led to validate the good hardness of the detectors to LHC intensity. Large size detectors (14 cm x 5 cm) were then tested. A preamplification stage, the GEM (Gas Electron Multiplier) has been added to compensate the increase of the noise and the strip capacitance. The GEM led to a significant decrease of the spark rate and an improvement of the gain margin. The long term ageing study of SGCs was performed with a 55Fe X-ray source of 6.4 keV during several months. The gain loss was estimated by the variation of the current, measured as a function of the integrated charge per centimeter of strip. The results show a loss of about 25% in 5 years of LHC operation at high intensity. The track electron reconstruction in the CMS tracker is important because elec- trons are involved in signature of several physics signals. A study has been done on the improvement of the reconstruction efficiency by introducing an energy loss of the electrons by Bremsstrahlung.
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Physique des Hautes Énergies - Expérience [hep-ex]. Université Claude Bernard - Lyon I, 2001. Français


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David Bouvet. Fiabilite à long terme des détecteurs gazeux à micropistes et de leur électronique de lecture dans les conditions de fonctionnement du LHC. Etude de la reconstruction des traces d'électrons dans le trajectographe du détecteur CMS.. Physique des Hautes Énergies - Expérience [hep-ex]. Université Claude Bernard - Lyon I, 2001. Français. <tel-00001247>

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