Detection of Bs→μ+μ− at the tevatron Run II and constraints on the SUSY parameter space

A measurement of the branching ratio for the rare decay mode Bs→μ+μ− at the Tevatron is an opportunity to test various supersymmetric scenarios. We investigate the prospects for studying this mode in Run II and estimate that CDF would be sensitive to this decay for a branching ratio >1.2×10−8 with 15 fb−1 (or, if a similar analysis holds for D0, >6.5×10−9 for the combined data). We calculate the branching ratio in minimal supergravity (mSUGRA) parameter space, and find that tanβ>30 can be probed. (This mSUGRA parameter space cannot be probed by direct production of SUSY particles at Run II.) Including other experimental constraints on the mSUGRA parameter space, one finds that CDF Bs→μ+μ− measurements would be able to cover the full mSUGRA parameter space for tanβ=50 if the muon gμ−2 anomaly exceeds ∼11×10−10, and about half the allowed parameter space for tanβ=40. A large branching ratio >7(14)×10−8 (feasible with only 2 fb−1) would be sufficient to exclude the mSUGRA model for tanβ⩽50(55). Dark matter neutralino–proton detection cross sections are examined in the allowed region, and should be large enough to be accessible to future planned experiments. Combined measurements of Bs→μ+μ−, the Higgs mass mh and the muon gμ−2 anomaly would be sufficient to determine the μ>0 mSUGRA parameters (or show the model is inconsistent with the data). We also briefly discuss the Bs→μ+μ− decay in R-parity violating models. There, for some models, the branching ratio can be large enough to be detected even for small tanβ and large m1/2.