Search for neutral Higgs bosons decaying to b(b)over-bar in the flipped 2HDM at future e- e+ linear colliders

In this study, assuming the type-Y (flipped) two-Higgs-doublet model (2HDM) in the Standard-Model-(SM) like scenario as the theoretical framework, observability of the additional heavy neutral Higgs bosons H and A is investigated through the signal process chain e(-)e(+) -> AH -> b (b) over barb (b) over bar at a linear collider operating at the center-of-mass energy of 1.5 TeV. The assumed signal process is highly motivated by the enhancements in the A/H -> b (b) over bar decays at relatively high tan beta values. Such enhancements result in the dominance of the mentioned decay modes even for Higgs masses above the threshold of the on-shell top quark pair production. Taking advantage of such a unique feature, several benchmark scenarios are studied. Simulating the detector response based on the SiD detector at the ILC, simulated events are analyzed to reconstruct the H and A Higgs bosons. The top quark pair production and Z/gamma production are the main SM background processes and are well under control. Results indicate that, the H and A Higgs bosons are observable with signals exceeding 5 sigma with possibility of mass measurement in all the tested scenarios. Specifically, the parameter space region enclosed with the mass ranges m(H) = 150-500 GeV and m(A) = 230-580 GeV with the A/H mass splitting of 80 GeV is observable at the integrated luminosity of 500 fb(-1).