Enhancement of B (B-bard→μ+μ-)/B (B-bars→μ+μ-) in the MSSM with modified minimal flavor violation and large tan β

We extend our previous analysis of the decays B-bard,s→μ+μ- in the minimal supersymmetric standard model (MSSM) to include gluino and neutralino contributions. We provide analytic formulas, valid at large values of tan β, for the scalar and pseudoscalar Wilson coefficients arising from neutral Higgs boson exchange diagrams with gluinos and neutralinos. Together with the remaining contributions (W±, H±, χ-tilde±), and assuming the Cabibbo-Kobayashi-Maskawa (CKM) matrix to be the only source of flavor violation, we assess their implications for the branching fractions B (B-bard,s→μ+μ-). Of particular interest is the quantity R≡B (B-bard→μ+μ-)/B (B-bars→μ+μ-), since (i) the theoretical errors cancel to a large extent, and (ii) it offers a theoretically clean way of extracting the ratio |Vtd/Vts| in the standard model, which predicts RSM∼|Vtd/Vts|2∼O(10-2). Exploring three different scenarios of modified minimal flavor violation (MFV), we find that part of the MSSM parameter space can accommodate large B-bard,s→μ+μ- branching fractions while being consistent with various experimental constraints. More importantly, we show that the ratio R can be as large as O(1), while the individual branching fractions may be amenable to detection by ongoing experiments. We conclude that within the MSSM with large tan β the decay rates of B-bard→μ+μ- and B-bars→μ+μ- can be of comparable size even in the case where flavor violation is due solely to the CKM matrix