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 τ lepton pairs. The search is performed with a data sample collected with the CMS detector from proton-proton collisions at the LHC at radical(s) p = 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 exclude previously unexplored regions of parameter space and provide constraints complementary to those from earlier searches.