New physics upper bound on the branching ratio of Bs→l+l-

We consider the most general new physics effective Lagrangian for b -> sl(+)l(-). We derive the upper limit on the branching ratio for the processes B-s -> l(+)l(-) where l = e, mu, subject to the current experimental bounds on related processes, B -> Kl(+)l(-) and B -> K*l(+)l(-). If the new physics interactions are of vector/axial-vector form, the present measured rates for B -> (K, K*)l(+)l(-) constrain B(B-s -> l(+)l(-)) to be of the same order of magnitude as their respective Standard Model predictions. On the other hand, if the new physics interactions are of scalar/pseudoscalar form, B -> (K, K*)l(+)l(-) rates do not impose any constraint on B-s -> l(+)l(-) and the branching ratios of these decays can be as large as present experimental upper bounds. If future experiments measure B(B-s -> l(+)l(-)) to be >= 10(-8) then the new physics giving rise to these decays has to be of the scalar/pseudoscalar form. (c) 2005 Published by Elsevier B.V.