  A relativistic quark model is extended to incorporate chiral and gauge
symmetries. We obtain the DD*pi and DD*gamma couplings and find that the ratio
Gamma(D*0->D0pi0)/Gamma(D*0->D0gamma) constrains the charm-quark mass close to
1.45 GeV. Large 1/mc corrections appear in the heavy-quark contribution to the
DD*gamma coupling. The model is extended further to describe seven excited D
meson states. We find that semileptonic B decays into the ground and excited D
meson states do not account for the total semileptonic decay width of the B0.
The nonresonant contributions to the processes B0->D(*)pi+ell+nu appear to be
large enough to account for the discrepancy.
