High Energy Physics Seminars

The determination of the element |Vub| of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix plays a central role in the search for flavour and CP violation beyond the Standard Model. In this seminar, we will present measurements of partial branching fractions for inclusive charmless semileptonic decays, B -> Xu l nu, in limited regions of phase space and the corresponding values of |Vub|, as extracted using several theoretical calculations. The invariant mass of the hadronic system, Mx, the squared invariant mass of the lepton pair, q2, and the variable P+ = Ex-|Px|, or one of their combinations, in the process B -> Xu l nu are used as discriminating variables to suppress semileptonic decays with charm. Partial branching fractions are measured as functions of the cuts on the above variables. Different theoretical models are used to compute acceptances and related uncertainties, thereby allowing to extract |Vub|. > These studies are performed on a sample of 383 million BB events collected at the Υ(4S) resonance, with the BaBar detector at the PEP-II e+e- storage rings