Full Description
This thesis presents a search for long-lived particles decaying into displaced electrons and/or muons with large impact parameters. This signature provides unique sensitivity to the production of theoretical lepton-partners, sleptons. These particles are a feature of supersymmetric theories, which seek to address unanswered questions in nature. The signature searched for in this thesis is difficult to identify, and in fact, this is the first time it has been probed at the Large Hadron Collider (LHC). It covers a long-standing gap in coverage of possible new physics signatures. This thesis describes the special reconstruction and identification algorithms used to select leptons with large impact parameters and the details of the background estimation. The results are consistent with background, so limits on slepton masses and lifetimes in this model are calculated at 95% CL, drastically improving on the previous best limits from the Large Electron Positron Collider (LEP).
Contents
Part 1: Introduction and Motivation.- Chapter 1: Introduction.- Chapter 2: Theory.- Part 2: The Experiment.- Chapter 3: The Large Hadron Collider.- Chapter 4: The ATLAS detector.- Chapter 5: Object Reconstruction.- Chapter 6: Data and Monte Carlo Samples.- Part 3: Long Lived Particle Context.- Chapter 7: Searching for Long Lived Particles.- Chapter 8: Experimental Context.- Part 4: Search for Displaced Leptons.- Chapter 9: Event Selection.- Chapter 10: Backgrounds.- Chapter 11: Signal Systematics.- Part 5: Results.- Chapter 12: Results.- Chapter 13: Interpretation.- Chapter 14: Conclusions and Future Improvements.
