Precise predictions for B -> Xs l+ l- in the large q^2 region

Abstract

The inclusive B -> Xs l+ l- decay rate in the large q^2 region (q^2 > m_{\psi'}^2) receives significant nonperturbative corrections. The resulting uncertainties can be drastically reduced by normalizing the rate to the B -> Xu l nu rate with the same q^2 cut, which allows for much improved tests of short distance physics. We calculate this ratio, including the order 1/m_b^3 nonperturbative corrections and the analytically known NNLO perturbative corrections. Since in the large q^2 region an inclusive measurement may be feasible via a sum over exclusive states, our results could be useful for measurements at LHCb and possibly for studies of B -> Xd l+ l-.