A Search for Gev Scale Dark Mediators Decaying to a Pair of Muons Using Data from the CMS Detector

Data from the LHC has enabled groundbreaking searches for physics beyond the standard model to be performed over the past decade. However, given that no concrete signatures of new physics have yet been observed at the TeV scale, many physicists have begun to explore the use of LHC data to probe lower energy processes with exceptional precision. This thesis will describe a search for prompt low-mass dimuon resonances performed using the 13 TeV proton-proton collision data collected by the Compact Muon Solenoid (CMS) detector during LHC Run-II. The analysis exploits a dedicated high-rate trigger stream which allows the recording of events below conventional momentum thresholds. The search is performed by looking for narrow resonance peaks in the dimuon mass continuum in the ranges from 1.1–2.6 and from 4.2–7.9 GeV. Model-independent limits on the production rate of a dimuon resonance within the experimental fiducial acceptance are set. Limits on parameters for a dark photon model and a two Higgs doublet model with an extra scalar, are also discussed.