Search for the nonresonant production of a pair of additional Higgs bosons in the Type-X two-Higgs-doublet model in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for the production of two additional Higgs bosons from an off-shell Z boson, where both additional particles decay to $\tau$ lepton pairs. The search is performed with a data sample collected with the CMS detector from proton-proton collisions at the LHC at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb${}^{-1}$. No deviation from the standard model background is observed. Exclusion limits are set on the Type-X two-Higgs-doublet model alignment scenario. These results rule out this model as an explanation to the potential tension between the experimental and theoretical values of the muon anomalous magnetic moment.