Leptonic and semileptonic decays ofBmesons

Abstract

Semileptonic decays are ideally suited to study the weak interaction as well as strong interaction effects in B-meson decays. In the last decade, precision studies of semileptonic B decays have been made possible by the large samples of B mesons collected at the B factories KEKB in Japan and PEP-II in the USA. Measurements of the charged-current semileptonic transitions b→qlν (q=u, c) allow for a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vcb and Vub and the masses of the b and c quarks, which are fundamental parameters of the standard model of particle physics. The values of |Vcb| and |Vub| are determined from measurements of inclusive B decays in combination with calculations of partial decay rates or from exclusive decays combined with theoretical predictions of hadronic form factors. Purely leptonic B decays B→lν (l=e, μ, τ) also provide access to |Vub|. They are theoretically simpler, but the available signal samples are still small. Decays involving a τ lepton, B→τν and B→D(*)τν, are sensitive to new physics, in particular, to charged Higgs bosons in models with an extended Higgs sector, and provide a window to the physics of the third generation. In this article, the measurements and theoretical descriptions of charged-current leptonic and semileptonic B decays and the status of |Vcb| and |Vub| determinations are reviewed. An overview of the theoretical approaches and the experimental techniques used in the study of these decays is also provided.