PHENOMENOLOGY OF HEAVY MESON CHIRAL LAGRANGIANS

The approximate symmetries of Quantum ChromoDynamics in the infinite h eavy quark (Q = c, b) mass limit (m(Q) --> infinity) and in the chiral limit for the light quarks (m(q) --> 0, q = u, d, s) can be used toge ther to build up an effective chiral lagrangian for heavy and light me sons describing strong interactions among effective meson fields as we ll as their couplings to electromagnetic and weak currents, including the relevant symmetry-breaking terms, The effective theory includes he avy (Q((q) over bar)) mesons of both negative and positive parity, lig ht pseudoscalars, as well as light vector mesons. We summarize the est imates for the parameters entering the effective lagrangian and discus s in particular some phenomenologically important couplings, such as g (BB pi). The hyperfine splitting of heavy mesons is discussed in deta il. The effective lagrangian allows for the possibility to describe co nsistently weak couplings of heavy (B, D) to light (pi, rho, K, etc.) mesons. The method has however its own limitations, due to the requir ement that the light meson momenta should be small, and we discuss how such limitations can be circumvented through reasonable ansatz on the form factors. Flavour conserving (e.g. B --> B gamma) and flavour ch anging (e.g. B --> Kgamma) radiative decays provide another held of a pplications of effective lagrangians; they are discussed together with their phenomenological implications. Finally, we analyze effective la grangians describing heavy charmonium- like (<(Q)over bar Q>) mesons a nd their strong and electromagnetic interactions. The role of approxim ate heavy quark symmetries for this case and the phenomenological test s of these models are also discussed.