Chiral dynamics and heavy quark symmetry in a solvable toy field-theoretic model

We study a solvable QCD-like toy theory, a generalization of the Nambu-Jona-Lasinio model, which implements chiral symmetries of light quarks and heavy quark symmetry. The chiral symmetric and chiral broken phases can be dynamically tuned. This implies a parity-doubled heavy-light meson system, corresponding to a (0^-, 1^-) multiplet and a (0⁺, 1⁺) heavy spin multiplet. Consequently the mass difference of the two multiplets is given by a Goldberger-Treiman relation and gA is found to be small. The Isgur-Wise function ξ(w), the decay constant fB and other observables are studied.