Large O(mc−2) nonperturbative corrections to the inclusive rate of the decay B → Xsγ

It is shown that the inclusive rate of the rare weak radiative decays B → Xsγ contains a series of nonperturbative corrections, whose ‘short distance’ scale is set by mc−1, rather than by mb−1. The first correction in this series is expressed through the chromomagnetic interaction of the b quark inside the B meson and the relative magnitude of the effect is determined by the ratio 〈B|bσ · Gb|B〉mc2. Though the magnitude of this first correction is s by a numerical coefficient, the sensitivity of the decay rate to the distance scale mc−1 may significantly limit the accuracy of purely perturbative predictions for the rate.