Search for long-lived particles decaying to displaced leptons in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

A search for new long-lived particles decaying to leptons is presented using proton-proton collisions produced by the CERN LHC at a center-of-mass energy of $13~\mathrm{TeV}$. Events are selected with two leptons (an electron [e] and a muon [$\mu$], two electrons, or two muons) that both have transverse impact parameter values between $0.01~\mathrm{cm}$ and $10~\mathrm{cm}$. Data used for the analysis were collected by the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of $113~\mathrm{fb}^{-1}$ for the e$\mu$ and $\mu\mu$ channels and $118~\mathrm{fb}^{-1}$ for the ee. The search is designed to be sensitive to a wide range of models with nonprompt e$\mu$, ee, and $\mu\mu$ final states. The results are interpreted with models involving top squarks that decay to displaced leptons via R-parity-violating interactions, a gauge-mediated supersymmetry breaking model with lepton superpartners that decay to gravitinos and displaced leptons, and a model involving exotic Higgs bosons that decay to long-lived scalars, which in turn decay to displaced leptons. This is the first search at CMS for displaced leptons at a center-of-mass energy of $13~\mathrm{TeV}$, and the first search at CMS for displaced leptons in the ee and $\mu\mu$ channels that does not require the leptons to come from a common displaced vertex.