Threshold resummed spectra in B -> Xu l nu decays in NLO (II)

Abstract

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 -> Xu l nu. By expanding our formulas, we obtain the coefficients of all the infrared logarithms at O(alphaS^2) and of the leading ones at O(alphaS^3). We explicitly show that the relation between these semileptonic spectra and the photon spectrum in the radiative decay B -> Xs gamma 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.

Comments: 16 pages, no figures