Bs,d→ℓ+ℓ− in a two-Higgs-doublet model Ori

We compute the branching fractions of Bs,d→ℓ+ℓ− in the type-II two-Higgs-doublet model with large tanβ . We find that the parameters of the neutral Higgs sector of the two-Higgs-doublet model cancel in the result, so that the branching fractions depend only on the charged Higgs mass and tanβ . For large values of tanβ and a charged Higgs mass above the bound from b→sγ , we find that the branching fractions can be enhanced by up to an order of magnitude or suppressed by up to a factor of two compared to the Standard Model result. We point out that previous calculations in the literature are gauge-dependent due to the omission of an important diagram, which gives the dominant contribution in the ʹt Hooft–Feynman gauge. We have analyzed in detail the region of the (MH+,tanβ) plane to be probed by searches for Bs→μ+μ− in Run II of the Tevatron. Since the branching fraction increases like tan4β , this decay mode is complementary to b→sγ and efficiently probes the large tanβ region. For tanβ=60 , an integrated luminosity of 20 fb −1 in an extended Run II will probe charged Higgs masses up to 260 GeV, if the background to Bs→μ+μ− is small. For the same value of tanβ , the LHC may be able to explore charged Higgs masses up to 1 TeV using this decay.