Search for dilepton resonances from decays of (pseudo)scalar bosons produced in association with a massive vector boson or top quark anti-top quark pair at $\sqrt{s}=13~\mathrm{TeV}$

A search for beyond the standard model scalar and pseudoscalar bosons that decay into pairs of electrons, muons, or tau leptons is presented. The search probes such new bosons that are produced in association with a $\mathrm{W}$ or $\mathrm{Z}$ boson, or a top quark anti-top quark pair, in events with with three or four leptons, including hadronic decays of tau leptons. The proton-proton collision dataset used in the analysis is collected by the CMS experiment at the LHC in $2016-2018$ at a center-of-mass energy of $13~\mathrm{TeV}$, and corresponds to an integrated luminosity of $138~\mathrm{fb}^{-1}$. The observations are consistent with the expectations from standard model processes. Upper limits at $95\%$ confidence level are placed on the product of cross section and branching fraction of such new particles with scalar, pseudoscalar, or Higgs-like couplings. Considering a single production, coupling, and decay scenario at a time, the observations exclude product of cross section and branching fraction values above $50-0.5~\rm{fb}$, $30-0.5~\rm{fb}$ and $200-1~\rm{fb}$ for new scalar, pseudoscalar, and Higgs-like bosons, respectively, that have a mass in the range $15-350~\mathrm{GeV}$ and exclusively decay into dielectron or dimuon pairs. Similarly, assuming such new bosons exclusively decay into pairs of tau leptons, the product of cross section and branching fraction values above $35-0.004~\rm{pb}$, $80-0.004~\rm{pb}$, and $250-0.008~\rm{pb}$ are excluded for scalar, pseudoscalar, and Higgs-like couplings, respectively. These are the most restrictive direct limits in these production and decay modes on an extension of the standard model with scalar or pseudoscalar particles.