"The dimuon mass distributions" of "Search for a narrow resonance lighter than 200 GeV decaying to a pair of muons in proton-proton collisions at $\sqrt{s} =$ 13 TeV"

A search is presented for a narrow resonance decaying to a pair of oppositely charged muons using $\sqrt{s}=13$ TeV proton-proton collision data recorded at the LHC. In the 45--75 and 110--200 GeV resonance mass ranges, the search is based on conventional triggering and event reconstruction techniques. In the 11.5--45 GeV mass range, the search uses data collected with dimuon triggers with low transverse momentum thresholds, recorded at high rate by storing a reduced amount of trigger-level information. The data correspond to integrated luminosities of 137 $\mathrm{fb}^{-1}$ and 96.6 $\mathrm{fb}^{-1}$ for conventional and high-rate triggering, respectively. No significant resonant peaks are observed in the probed mass ranges. The search sets the most stringent constraints to date on a dark photon in the $\sim$30--75 and 110--200 GeV mass ranges.