Scattering lengths of Nambu-Goldstone bosons off $ mesons and dynamically generated heavy-light mesons

Recent lattice QCD simulations of the scattering lengths of Nambu-Goldstone bosons off the $ mesons are studied using unitary chiral perturbation theory. We show that the Lattice QCD data are better described in the covariant formulation than in the heavy-meson formulation. The ^ _{s0}(2317)$ can be dynamically generated from the coupled-channels $ interaction without \textit{a priori} assumption of its existence. A new renormalization scheme is proposed which manifestly satisfies chiral power counting rules and has well-defined behavior in the infinite heavy-quark mass limit. Using this scheme we predict the heavy-quark spin and flavor symmetry counterparts of the ^ _{s0}(2317)$.