Masses of physical scalars in two Higgs doublet models

Abstract: We find bounds on scalar masses resulting from a criterion of naturalness, in a broad class of two Higgs doublet models (2HDMs). Specifically, we assume the cancellation of quadratic divergences in what are called the type I, type II, lepton-specific and flipped 2HDMs, with an additional U(1) symmetry. This results in a set of relations among masses of the physical scalars and coupling constants, a generalization of the Veltman conditions of the Standard Model. Assuming that the lighter $CP$-even neutral Higgs particle is the observed scalar particle of mass $\sim$125 GeV, and imposing further the constraints from the electroweak T-parameter, stability, and perturbative unitarity, we calculate the range of the mass of each of the remaining physical scalars.