Thesis or Dissertation Search for long-lived supersymmetry particle by signature of a high track-multiplicity displaced vertex using the LHC-ATLAS Experiment

Pettersson, Nora Emilia  ,  Petterson, Nora

Long-lived supersymmetry (SUSY) particles decaying within the tracking volume in the LHC-ATLAS detector can be reconstructed as a displaced vertex by fitting a vertex from the tracks, arising from the charged daughter particles. A search for such a signature has been conducted using s=8 TeV data collected during 2012 at an integrated luminosity of 20.3 fb-1. In the absence of any signal of new physics, limits on the production cross-sections are set. Interpreted in the context of R-Parity violating (RPV) SUSY, where the lightest SUSY particle decay to purely standard model particles through various RPV couplings. The excluded upper limits cross-section varies depending on lifetime of the long-lived particles and the targeted coupling, with a value of 0.3 fb in the best case scenario. A model-independent limit on the cross-section is set at 0.14 fb including all uncertainties, yielding an significant improvement from previous the result of 5.4 fb.

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