  We present an investigation of the inclusive semileptonic decay widths of the
heavy baryons Lambda_Q and Xi_Q, (Q=b,c) performed within a relativistic
constituent quark model, formulated on the light-front. In a way conceptually
similar to the deep-inelastic scattering case, the H_Q baryon inclusive width
is expressed as the integral of the free Q-quark partial width multiplied by a
bound-state factor related to the Q-quark distribution function in the H_Q. The
non-perturbative meson structure is described through the quark-model wave
functions, constructed via the Hamiltonian light-front formalism using as input
the Kalman-Tran-D'Souza equal time wave functions. A link between spectroscopic
quark models and the H_Q decay physics is obtained in this way. It is shown
that the bound-state effects and the Fermi motion of the b-quark remarkably
reduce the decay rate with respect to the free-quark result. Our predictions
for the BR(Lambda_c ->X_s e nu_e) and BR(Lambda_b->X_c e nu_e) decays are in
good agreement with existing data.
