Large O ( m − 2 c ) nonperturbative correction to the inclusive rate of the decay B →

Large O(m −2 c) nonperturbative correction to the inclusive rate of the decay B → X s γ. Abstract It is shown that the inclusive rate of the rare weak radiative decays B → X s γ contains a nonperturbative correction, whose 'short distance' scale is set by m −1 c rather than by m −1 b. This correction 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| ¯ b σ ·G b|B/m 2 c. The correction is found to be negative and amounts (in the lowest order in α s) to approximately 20% reduction of the rate in comparison with the perturbative result. Possible further implications of the presence of the distance scale m −1 c in the operator product expansion for inclusive decay rates of b hadrons are briefly discussed.