Studies of supersymmetry models for the ATLAS experiment at the Large Hadron Collider

• Main Author: Barr, A. J.
• Published: University of Cambridge 2003
• Subjects: 531.16
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596404

This thesis demonstrates that supersymmetry can be discovered with the ATLAS experiment even if nature conspires to choose one of two rather difficult cases. In the first case where baryon-number is weakly violated, the lightest supersymmetric particle decays into three quarks. This leads to events with a very large multiplicity of jets which presents a difficult combinatorial problem at a hadronic collider. The distinctive property of the second class of model - anomaly-mediation - is the near degeneracy of the super-partners of the SU(2) weak bosons. The heavier charged wino decays producing its invisible neutral partner, the presence of which must be inferred from the apparent non-conservation of transverse momentum, as well as secondary particle(s) with low transverse momentum which must be extracted from a large background. Monte-Carlo simulations are employed to show that for the models examined not only can the distinctive signature of the model can be extracted, but that a variety of measurements (such as of sparticle masses) can also be made. The final two chapters present an investigation into part of the experimental hardware which will be vital for these analyses. Beam tests of ATLAS semiconductor tracker modules demonstrate that this sub-detector can be expected to perform to its specification, providing the good spatial resolution and efficiency with low noise, even after the equivalent of ten years of irradiation.