UCLA

This thesis presents a search for new long-lived particles decaying to two muons in the Compact Muon Solenoid (CMS) detector using proton-proton collision data taken at √s = 13 TeV corresponding to 96.6 fb−1 of integrated luminosity during the Run 2 of the Large Hadron Collider (LHC). The search spans the full extent of the CMS detector and probes vertices displaced from the interaction point ranging from less than a millimeter to multiple meters. No evidence for beyond the standard model physics is observed. Results are interpreted in the context of both scalar and vector models for the long-lived particle. We also present a detailed description of a novel algorithm for the endcap muon system of CMS which improves muon resolution of the Level-1 Trigger to be implemented for the upcoming Run 3 data taking period.