2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/206488In order to extract the Cabibbo-Kobayashi-Maskawa matrix element |V_{ub}| from B -> X_u l anti-nu_l decays, the overwhelming background from B -> X_c l anti-nu_l decays must be reduced by appropriate acceptance cuts. We study the non-perturbative effects due to the motion of the b quark inside the B meson on the phenomenologically relevant decay distributions of B -> X_u l anti-nu_l in the presence of such cuts in a comparative analysis based on shape functions and the parton model in the light-cone limit. Comparisons with recent data from the CLEO, BABAR, and BELLE collaborations favor the shape-function approach.27 pages, 11 figuresHigh Energy Physics - Phenomenologytext