TTP02-29 Subleading Light-cone distributions functions in the decays $\Lambda_b \to X_s \gamma$ and $\Lambda_b \to X_u \ell \bar{\nu}_\ell$

In this paper we investigate the subleading twist corrections to the photon energy spectrum in the decay Lambda_b → X_s \gamma and to the lepton energy spectrum in Lambda_b → X_u l \bar{\nu}. As a first step we rederive the matching coefficients of the subleading twist using a much simpler method. Parametrizing the matrix elements for Lambda_b and using reparametrization invariance, we show that the energy spectra close to the endpoints are given in terms of only a single universal function.