Enhancement of B((B)over-bard→μ+μ-)/B((B)over-bars→μ+μ-) in the MSSM with modified minimal flavor violation and large tan β -: art. no. 074021

We extend our previous analysis of the decays (B) over bar (d,s)-->mu(+)mu(-) in the minimal supersymmetric standard model (MSSM) to include gluino and neutralino contributions. We provide analytic formulas, valid at large values of tan beta, 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+/-, chi(+/-)), 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) over bar (d,s)-->mu(+)mu(-)). Of particular interest is the quantity R=B ((B) over bar (d)-->mu(+)mu(-))/B ((B) over bar (s)-->mu(+)mu(-)), since (i) the theoretical errors cancel to a large extent, and (ii) it offers a theoretically clean way of extracting the ratio \V-td/V-ts\ in the standard model, which predicts R(SM)similar to\V-td/V-ts\(2)similar toO(10(-2)). Exploring three different scenarios of modified minimal flavor violation ((MFV) over bar), we find that part of the MSSM parameter space can accommodate large (B) over bar (d,s)-->mu(+)mu(-) 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 beta the decay rates of (B) over bar (d)-->mu(+)mu(-) and (B) over bar (s)-->mu(+)mu(-) can be of comparable size even in the case where flavor violation is due solely to the CKM matrix.