Search for physics beyond the standard model in events with two same-sign leptons or at least three leptons and jets in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$.

A data sample of events from proton-proton collisions with two isolated same-sign leptons or at least three leptons, and at least two jets, is studied in a search for signatures of new physics phenomena by the CMS Collaboration at the LHC. The data correspond to an integrated luminosity of $137~\mathrm{fb}^{-1}$, at a center-of-mass energy of $13~\mathrm{TeV}$. The properties of the events are consistent with expectations from standard model processes, and no excess yield is observed. Exclusion limits at $95\%$ confidence level are set on cross sections for the pair production of gluinos or squarks for various decay scenarios in the context of supersymmetry models conserving or violating R-parity. The observed lower mass limits are as high as $2.1~\mathrm{TeV}$ for gluinos, and $0.9~\mathrm{TeV}$ for top and bottom squarks.