Non-Universal Effects in Semi-Inclusive B Decays

We show that most spectra in the semileptonic decay B→Xu+l+νl, such as for example the distribution in the light-cone momentum recently considered, do not have the same long-distance structure of the photon spectrum in the radiative decay B→Xs+γ. On the contrary, the semileptonic distribution in the final hadron energy EX is connected to the radiative spectrum via short-distance factors only. The EX distribution also has a specific infrared structure known as the “Sudakov shoulder”. We also discuss an explicit check of the resummation formula for the semileptonic decays, based on a recent second-order computation.