Search for new Higgs bosons through same-sign top quark pair production in association with a jet in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

A search is presented for new Higgs bosons in proton-proton collision events in which a same-sign top quark pair is produced in association with a jet, via the $\mathrm{cg}\rightarrow\mathrm{tH/A}\rightarrow\mathrm{tt\overline{c}}$ and $\mathrm{cg}\rightarrow\mathrm{tH/A}\rightarrow\mathrm{tt\overline{u}}$ processes. Here $\mathrm{H}$ and $\mathrm{A}$ represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on proton-proton collision data collected at a center-of-mass energy of $13~\mathrm{TeV}$ with the CMS detector at the LHC, corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$. Final states with a same-sign lepton pair in association with a charm or up quark are considered. New Higgs bosons in the $200-1000~\mathrm{GeV}$ mass range are targeted in the search, for scenarios in which either $\mathrm{H}$ or $\mathrm{A}$ appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed, and exclusion limits are derived in the context of the g2HDM. Depending on the g2HDM signal assumptions, the mass of a new Higgs boson below 1 TeV and corresponding new Yukawa couplings between 0.4 and 1 are excluded at the $95\%$ confidence level.