Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at $\sqrt{s}=13\,\mathrm{TeV}$

A combination of searches for the production of a pair of top squarks using $137\,\mathrm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=13\,\mathrm{TeV}$ collected by the CMS experiment is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, and 2 leptons and additional jets. New results for regions of parameter space where the kinematics of top squark pair production and top quark pair production are very similar, owing to the mass difference between the top squark and the neutralino being close to the top quark mass, are presented. Depending on the model, the combined result excludes a top squark mass up to $1325\,\mathrm{GeV}$ for a massless lightest supersymmetric particle (LSP), and an LSP mass up to $700\,\mathrm{GeV}$ for a top squark mass of $1150\,\mathrm{GeV}$. Top squarks with mass from $145$ to $275\,\mathrm{GeV}$, for LSP mass from 0 to $100\,\mathrm{GeV}$, with a small mass difference between the top squark and the LSP of less than $30\,\mathrm{GeV}$, are excluded for the first time with CMS data. In an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair, upper limits on the mediator particle masses of up to $420\,\mathrm{GeV}$ are set.