Study of charmless B meson semileptonic decays in an inclusive model

A precision measurement of V_ub will be achieved only when the hadronic matrix element needed to describe the b → u semileptonic decays is modeled in a reliable fashion. In this letter predictions for kinematical variables which are very sensitive to the underlying hadronic dynamics are developed in an inclusive parton model. Particular emphasis will be given to the end-point of the lepton spectrum, which is of crucial importance for the interpretation of present experimental data. It will be shown that this approach gives a value of |V_ub/V_cb|² which can be up to 35% higher than the one quoted in recent reports and in better agreement with previous measurements of excess leptons from charmless B meson semileptonic decays.