Search for heavy 2HDM Higgs bosons in A->ZH with H->ttbar and semi-leptonic decays of the top quarks

A search for a heavy Higgs boson A(H) decaying into a Z boson and a lighter Higgs boson H(A) is presented, and is interpreted in a model motivated by electroweak baryogenesis. The search uses the full LHC Run 2 dataset of pp collisions at sqrt(s)=13TeV collected with the CMS detector, corresponding to an integrated luminosity of 138fb(^-1). The experimental signature is doubly resonant, with the lighter of the two heavy Higgs bosons decaying to a top quark pair and the Z required to decay to charged leptons. The search is performed over the mass ranges of 500-2000 GeV for the heavier of the two and 300-1800 GeV for the lighter one, which contains phase space compatible with experimental constraints and a first-order electroweak phase transition in the framework of the two-Higgs double model (2HDM). The analysis is expected to be most sensitive for heavy resonances just above the di-top mass threshold, in the regions of small tanb and large mass splittings between the A and H bosons.