A Search for Displaced Leptons in the ATLAS Detector

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).

Nominated as an outstanding PhD thesis by the University of Chicago Describes innovative new data analysis methods for searches for new physics at the LHC Provides an accessible overview of the Standard Model and experiments at the LHC

Autorentext

Dr. Lesya Horyn is a particle physics researcher. She grew up in New York, where her parents fostered a love of science and learning.. She began doing physics research at the American Museum of Natural History in New York City. She then received a Bachelor of Science from Tufts University, where she began working on the ATLAS experiment with collaborators both at Tufts and as a Research Experience for Undergraduates student at Duke University. She then completed a Ph. D at University of Chicago, where she performed the work presented in this thesis under the supervision of Professor Young-Kee Kim and Dr. Tova Holmes. She currently works on the CMS experiment with Fermi National Accelerator Laboratory and resides in Geneva, Switzerland. In her spare time, she likes reading, cycling, and traveling near and far.

Inhalt
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.