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Instanton Contribution to B → X u e ¯ ν Decay

We study instanton eﬀects on inclusive semileptonic b → u decay using the heavy quark eﬀective ﬁeld theory and the operator product expansion. The eﬀect contributes not only to the hadronic matrix element but also to the coeﬃcient functions in the operator product expansion. We ﬁnd that the coeﬃcient function is singular near the boundaries of the phase space. In order to use perturbative QCD reliably, it is necessary to introduce smearing near the boundary. However the instanton contribution to b → c decay seems negligibly small.