Charged Higgs boson contribution to Bq- → ν and B → (P,V) ν in a generic two-Higgs doublet model CHARGED HIGGS BOSON CONTRIBUTION to ... CHUAN-HUNG CHEN and TAKAAKI NOMURA

We comprehensively study the charged Higgs boson contributions to the leptonic Bq-→ ν (q=u, c) and semileptonic B→Xqν (Xu=π, ρ; Xc=D, D∗) decays in the type-III two-Higgs doublet model. We employ the Cheng-Sher ansatz to suppress the tree-level flavor-changing neutral currents in the quark sector. When the strict constraints from the ΔB=2, b→sγ, and pp(bb)→H/A→τ+τ- processes are considered, parameters χtqu from the quark couplings and χ from the lepton couplings dictate the leptonic and semileptonic B decays. It is found that, when the measured Bu-→τν and indirect bound of Bc-→τν obtained by LEP1 data are taken into account, R(D) and R(π) can have broadly allowed ranges; however, the values of R(ρ) and R(D∗) are limited to approximately the standard model (SM) results. We also find that the same behaviors also occur in the τ-lepton polarizations and forward-backward asymmetries (AFBXq,τ) of the semileptonic decays, with the exception of AFBD∗,τ, for which the deviation from the SM due to the charged Higgs boson effect is still sizable. In addition, the q2-dependent AFBπ,τ and AFBD,τ can be very sensitive to the charged Higgs boson effects and have completely different shapes from the SM.