Measuring the fermionic couplings of the Higgs boson at future colliders as a probe of a nonminimal flavor structure

We study the fermionic couplings of the neutral Higgs bosons in the two Higgs doublet model, assuming a four-texture structure for the Yukawa matrices. We then derive the low-energy constraints on the model, focusing in b-quark and lepton physics, and apply them to study Higgs boson detection at future colliders. We show that the bound on the flavor-violating parameter χ_sb obtained from the contribution due to the bs̅ h⁰ coupling to the decay b→s+γ (roughly of the order 10^-1–10^-2) is approximately a factor 10 more restrictive than that obtained from the current bound on Γ(B_s⁰→μ^-μ⁺) (which gives a bound on χ_sb of the order 10⁰–10^-1). On the other hand, the analysis of the LFV decay μ→eγ leads to the constraint χ_μτ≲10^-2. The observation of a Higgs signal at a future muon collider would confirm the results of these constraints for tan⁡β≲15, while for larger values of tan⁡β such colliders will not improve the bounds derived from low-energy data. At a hadron collider it is further possible to study the Higgs boson coupling h⁰bb̅ by searching for the associated production of the Higgs boson with bb̅ pairs.