Constraining the two-Higgs-doublet-model parameter space

We confront the two-Higgs-doublet model with a variety of experimental constraints as well as theoretical consistency conditions. The most constraining data are the B̄→Xₛγ decay rate (at low values of M_H^±), and Δρ (at both low and high M_H^±). We also take into account the BB̄ oscillation rate and Rb, or the width Γ(Z→bb̄) (both of which restrict the model at low values of tanβ), and the B^-→τν_τ decay rate, which restricts the model at high tanβ and low M_H^±. Furthermore, the LEP2 nondiscovery of a light, neutral-Higgs boson is considered, as well as the muon anomalous magnetic moment. Since perturbative unitarity excludes high values of tanβ, the model turns out to be very constrained. We outline the remaining allowed regions in the tanβ-M_H^± plane for different values of the masses of the two lightest neutral-Higgs bosons, and describe some of their properties.