Signatures of supersymmetry and Yukawa unification in Higgs decays

We show that the branching ratio Rb/τ≡BR(h0→b̄b)/BR(h0→τ+τ−) of the Higgs boson h0 may usefully differentiate between the Higgs sectors of the Minimal Supersymmetric Standard Model (MSSM) and non-supersymmetric models such as the Standard Model or its two Higgs doublet extensions. Although at tree level Rb/τ is the same in all these models, only in the MSSM can it receive a large radiative correction, for moderate to large values of the parameter tanβ. Such large corrections are motivated in supersymmetric unified schemes wherein the Yukawa couplings of the b-quark and the τ-lepton are equal at the unification scale; otherwise the b-quark mass prediction is too large by 15–30% for most of parameter space. Thus accurate measurements of the Higgs branching ratios can probe physics at the unification scale. The branching ratio of h0 into charm quarks, as well as of the other Higgs bosons (H0,A0) into b̄b, τ+τ−, c̄c can provide additional information about the supersymmetric nature of the Higgs sector.