Search for prompt production of a GeV scale resonance decaying to a pair of muons in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}

A search for prompt low-mass dimuon resonances is performed using the 13$~\mathrm{TeV}$ proton-proton collision data collected by the Compact Muon Solenoid (CMS) detector during the 2017--2018 operation of the CERN's Large Hadron Collider and corresponding to an integrated luminosity of 96.6$~\mathrm{fb}^{-1}$. The search exploits a dedicated scouting trigger stream allowing CMS to record events with two muons with transverse momenta as low as 3$~\mathrm{GeV}$ by trading off recording the full event information. 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$~\mathrm{GeV}$. The largest excess is observed in the boosted dimuon category at a dimuon mass of 2.41$~\mathrm{GeV}$ with the local significance of 3.2 standard deviations, with the global significance of the excess being 1.3 standard deviations. Model-independent limits on production rates of dimuon resonances within the experimental fiducial acceptance are set. Limits on parameters for two specific models, a dark photon model and a two Higgs doublet model with an extra scalar, are also set. $$\textit{This document has been revised with respect to the version dated March 11th, 2023.}$$