Search for long-lived particles decaying into two muons in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ using data collected with high rate triggers

A search for displaced dimuon resonances is performed using proton-proton collisions at a center-of-mass energy of $13~\mathrm{TeV}$, collected by the CMS experiment at the LHC in 2017$-$2018, corresponding to an integrated luminosity of $101~\mathrm{fb}^{-1}$. The data sets used in this search were collected using a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of trigger-level information, in order to explore otherwise inaccessible phase space at low dimuon mass and non-zero displacement from the interaction point. We find no significant excess, and use the data to set stringent constraints on a wide range of mass and lifetime hypotheses for models of physics beyond the standard model where a Higgs boson decays to a pair of long-lived dark photons, or where a long-lived scalar resonance arises from the decay of a B hadron.