Power-enhanced leading-logarithmic QED corrections to Bq→ μ+μ−

Abstract

A bstract We provide a systematic treatment of the previously discovered power- enhanced QED corrections to the leptonic decay B q → μ + μ − ( q = d, s ) in the frame- work of soft-collinear effective theory (SCET). Employing two-step matching on SCETI and SCET II , and the respective renormalization group equations, we sum the leading- logarithmic QED corrections and the mixed QED-QCD corrections to all orders in the couplings for the matrix element of the semileptonic weak effective operator Q 9 . We pro- pose a treatment of the B -meson decay constant and light-cone distribution amplitude in the presence of process-specific QED corrections. Finally we include ultrasoft photon radiation and provide updated values of the non-radiative and radiative branching fractions of B q → μ + μ − decay that include the double-logarithmic QED and QCD corrections.