Current Status of the Standard Model Prediction for the Bs → μ+μ− Branching Ratio

The rare decay Bs→μ+μ− provides an important constraint on possible deviations from the Standard Model in b-s-ℓ-ℓ interactions. The present weighted average of its branching ratio measurements amounts to (3.34±0.27)×10−9, which remains in good agreement with the theoretical prediction of (3.64±0.12)×10−9 within the Standard Model. In the present paper, we review calculations that have contributed to this prediction and discuss the associated uncertainties.