B(Bs → μ+, μ-) as an electroweak precision test

Using an effective-theory approach, we analyze the impact of B(B-s -> mu(+), mu(-)) in constraining newphysics models that predict modifications of the Z-boson couplings to down-type quarks. Under motivated assumptions about the flavor structure of the effective theory, we show that the bounds presently derived from B(B-s -> mu(+), mu(-)) on the effective Z-boson couplings are comparable (in the case of minimal flavor violation) or significantly more stringent (in the case of generic partial compositeness) with respect to those derived from observables at the Z peak. (C) 2013 Elsevier B.V. All rights reserved.