Università di Roma “La Sapienza”,

We resum to next-to-leading order the distribution in the ratio of the invariant hadron mass mX to the total hadron energy EX and the distribution in mX in the semileptonic decays B → Xulν. By expanding our formulas, we obtain the coefficients of all the infrared logarithms at O(αS) and of the leading ones at O(α 3 S). We explicitly show that the relation between these semileptonic spectra and the photon spectrum in the radiative decay B → Xsγ is not a purely short-distance one. There are long-distance effects in the semileptonic spectra which are not completely factorized by the structure function as measured in the radiative decay and have to be modelled in some way. e-mail address: [email protected] e-mail address: [email protected] e-mail address: [email protected]