Connection between inclusive semileptonic decays of bound and free heavy quarks - art. no. 114024

A relativistic constituent quark model, formulated on the light front, is u sed to derive a new parton approximation for the inclusive semileptonic dec ay width of the B meson. A simple connection between the decay rate of a fr ee heavy quark and the one of a heavy quark bound in a meson or in a baryon is established. The main features of the new approach are the treatment of the b quark as an on-mass-shell particle and the inclusion of the effects arising from the b quark transverse motion in the B meson. In a way concept ually similar to the deep-inelastic scattering case, the B meson inclusive width is expressed as the integral of the free b quark partial width multip lied by a bound-state factor related to the b-quark distribution function i n the B meson. The nonperturbative meson structure is described through var ious quark-model wave functions, constructed via the Hamiltonian light fron t formalism, using as input both relativistic and nonrelativistic potential models. A link between spectroscopic quark models and B-meson decay physic s is obtained in this way. Our predictions for the B-->X(c)l nu(l) and B--> X(u)l nu(l) decays are used to extract the CKM parameters \V-cb\ and \V-ub\ from available inclusive data. After averaging over the various quark mode ls adopted and including leading-order perturbative QCD corrections, we obt ain \V-cb\ = (43.9+/-0.7(exp)+/-1.8(th)) x 10(-3) and \V-ub\ = (3.83+/-0.48 (exp)+/-0.14(th)) x 10(-3), implying \V-ub/V-cb\ = 0.089+/-0.011(exp)+/-0.0 05(th), in nice agreement with existing predictions. [S0556-2821(99)02621-1 ].