Nonperturbative O(mc−2) effects in B→Xsγ from heavy quark effective theory

The nonperturbative contribution, suppressed by powers of the charm quark mass mc, in the inclusive decay B→Xsγ is analyzed in the context of heavy quark effective field theory (HQEFT). According to previous analyses, the leading effects of O(1/mc2) arise from an external gluon attached to a charm quark loop and can be expressed in terms of the chromomagnetic interaction of the b quark inside the B meson. This is also true at leading order in the HQEFT approach. However the structure of higher-dimensional operators is different because the effects of external gluons alone do not give a complete set of operators. A systematic method to derive all the high-dimensional operators can be obtained in the HQEFT scheme using the operator product expansion.