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Compact Muon Solenoid
LHC, CERN

CMS-PAS-EXO-21-008
Search for long-lived particles decaying in the CMS muon detectors in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
Abstract: A search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. The data sample consists of 138 fb$ ^{-1} $ of proton-proton collisions at $ \sqrt{s}= $ 13 TeV, recorded at the LHC in 2016-2018. A unique technique is employed to reconstruct decays of LLPs in the muon detectors. The search is sensitive to LLP masses from 0.4 to 55 GeV and a broad range of LLP decay modes, including decays to a pair of quarks, kaons, pions, electrons, photons, or $ \tau $ leptons. No excess of events above the standard model background is observed. The most stringent LHC limits to date on the branching fraction of the Higgs boson to a pair of LLPs with masses below 10 GeV are set. This search also provides the most stringent limit for proper decay lengths in the range 0.04-0.4 m and above 4 m for an LLP mass of 15 GeV, in the range 0.3-0.9 m and above 3 m for an LLP mass of 40 GeV, and above 0.8 m for an LLP mass of 55 GeV. Finally, this search sets the first LHC limits on a dark quantum chromodynamic sector that couples to the Higgs boson through gluon, Higgs, photon, vector, and dark photon portals, and is sensitive to branching fractions of the Higgs boson to dark quarks as low as 10$^{-3} $.
CMS Publications
Compact Muon Solenoid
LHC, CERN