B meson semileptonic decays

Experimental studies of B meson semileptonic decays have reached a level of great sophistication, but several issues still need to be addressed. Progress will involve a close interplay between experimental and theoretical work. Experimental studies that are crucial to further progress include: - a full understanding of the composition of the B meson semileptonic width; - a precise determination of the OPE expansion parameters; - overall checks of the consistency of the theoretical picture, including extent of quark-hadron duality violation and effects of neglected terms in the perturbative and nonperturbative expansion; - study of inclusive charmless semileptonic decays in selected phase space domains sensitive to different theoretical effects; - detailed studies of the kinematic properties of charmless semileptonic decays with tagged samples. The theoretical challenge is to increase the reliability and the precision of the evaluation of hadronic matrix elements in a regime where non-perturbative effects are quite important. Consequently. B meson semileptonic decays are a crucial tool in our studies of the quark mixing parameters Vcb and Vub. The completion of this complex and ambitious program will lead to precise measurements of the CKM parameters and thus will provide a unique contribution to the multifaceted challenge to the Standard Model through the study of beauty and charm decays. In this paper the interplay between experimental and theoretical challenges to achieve precision in the determination of these fundamental parameters are discussed