Inclusive Measurements of Vub from BaBar

摘要

The Cabibbo-Kobayashi-Maskawa (CKM) matrix element V(sub ub) is a fundamental parameter of the Standard Model, representing the coupling of the b quark to the u quark. It is one of the smallest and least known elements of the CKM matrix. With the increasingly precise measurements of decay-time-dependent CP asymmetries in B-meson decays, in particular the angle (beta), improved measurements of the magnitude of V(sub ub) will allow for stringent experimental tests of the Standard Model mechanism for CP violation. The extraction of V(sub ub) is a challenge, both theoretically and experimentally. Theoretically, the weak decay rate for b yields uev can be calculated at the parton level. It is proportional to V(sub ub)/(sup 2) and m(sub b)(sup 5), where m(sub b) is the b-quark mass. To relate the B-meson decay rate to (V(sub ub)), the parton-level calculations have to be corrected for perturbative and non-perturbative QCD effects. These corrections can be calculated using various techniques: heavy quark expansions (HQE) and QCD factorization. They make use of specific assumptions and are affected by different uncertainties.