Comment on nonperturbative effects in $B\to X_sγ$

Abstract

Uncertainties in the theoretical prediction for the inclusive $B\to X_sγ$ decay rate are discussed. We emphasize that there is no operator product expansion for this process. Nonetheless, some nonperturbative effects involving a virtual $c\bar c$ loop are calculable using the operator product expansion. They give a contribution to the decay rate that involves the B meson matrix element of an infinite tower of operators. The higher dimension operators give effects that are only suppressed by powers of $m_bΛ_{QCD}/m_c^2 \sim 0.6$, but come with small coefficients.