The evaluation of silicon microstrip detectors for the ATLAS semiconductor tracker and supersymmetry studies at the Large Hadron Collider

• Main Author: Drage, L. M.
• Published: University of Cambridge 2000
• Subjects: 531.16
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598635

The ATLAS detector will surround one of the interaction points of the Large Hadron Collider at the European Centre for Particle Physics. The ATLAS Semiconductor Tracker (SCT) will provide precision tracking of charged particles using silicon microstrip detectors. The SCT silicon detectors must operate for at least 10 years in a high radiation environment, in a 2 T magnetic field and with non-normally incident particles. The first half of this thesis investigates the performance of prototype detectors for the SCT using a 180 GeV/c pion beam. Two beam tests are documented. The first is used to compare the performance of two different silicon microstrip detector designs after detector irradiation to a fluence equivalent to 10 years of ATLAS operation. Detector efficiency, noise occupancy, precision and the charge division between detector strips are studied. The charge produced in a detector by incident pions is compared with the predictions of Landau theory. The second beam test compares the performance of an irradiated detector and an unirradiated detector of the selected SCT design in a magnetic field and with non-normally incident pions. The performance of detectors in both beam tests are found to mostly satisfy design specifications. The accurate measurement of the momentum and position of charged particles will be essential when searching for new physics. Supersymmetry (SUSY) is the most theoretically favoured extension of the Standard Model, the current theory of fundamental particles and interactions. The majority of studies of the ATLAS potential to discover and investigate SUSY particles have assumed that a discrete symmetry, R-parity, is conserved. In this thesis, an R-parity and baryon number violating supergravity model is considered. A new version of the HERWIG Monte Carlo event generator which correctly incorporates R-parity violating vertices was used with ATLFAST, a particle level simulation of the ATLAS detector. An algorithm to measure three sparticle masses is presented. It is shown that the errors on these measurements are dominated by uncertainties in jet energy scale corrections.