Search for Long-Lived Particles Decaying to Displaced Dimuons at 13 TeV and Study of Neutron-Induced Background Hits in the Muon System of the Compact Muon Solenoid

This thesis presents a search for new long-lived particles decaying to two muons in the CMS detector with pp collision data taken at $\sqrt{s} = 13\,\mathrm{TeV}$ corresponding to $36.3\,\mathrm{fb}^{-1}$ of integrated luminosity during Run~2 of the LHC. Such decays would appear as dimuon vertices displaced with respect to the pp interaction point. The search presented in this thesis uses only the muon system in order to probe the longest lifetimes to which the LHC experiments are sensitive. The results are interpreted in terms of a benchmark model consisting of exotic Higgs bosons decaying to long-lived scalar bosons, but are presented in an approximately model-independent way suitable for reinterpretation. No excess is observed. The appendix describes a study of neutron-induced background in CMS endcap muon chambers.