Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The collaboration
CMS-SUS-18-004, 2021.

Abstract (data abstract)
A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at $\sqrt{s} = 13~\text{TeV}$ collected in the three-year period $2016-2018$ by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to $137~\text{fb}^{-1}$. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at $95\%$ confidence level are set on $\tilde{\chi}^0_2/\tilde{\chi}^\pm_1$ masses up to $275~\text{GeV}$ for a mass difference of $10~\text{GeV}$ in the wino-bino case, and up to $205(150)~\text{GeV}$ for a mass difference of $7.5(3)~\text{GeV}$ in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter $\mu$ up to $180~\text{GeV}$ with the bino mass parameter $M_1$ at $800~\text{GeV}$. In the top squark interpretation, exclusion limits are set at top squark masses up to $540~\text{GeV}$ for four-body top squark decays and up to $480~\text{GeV}$ for chargino-mediated decays with a mass difference of $30~\text{GeV}$.