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

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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 (${0}^{\ensuremath{-}}$, ${1}^{\ensuremath{-}}$) multiplet and a (${0}^{+}$, ${1}^{+}$) heavy spin multiplet. Consequently the mass difference of the two multiplets is given by a Goldberger-Treiman relation and ${g}_{A}$ is found to be small. The Isgur-Wise function $\ensuremath{\xi}(w)$, the decay constant ${f}_{B}$ and other observables are studied.