The approximate symmetries of Quantum ChromoDynamics in the infinite heavy quark (Q = c, b) mass limit (mQ → ∞) and in the chiral limit for the light quarks (mq → 0, q = u, d, s) can be used together to build up an effective chiral lagrangian for heavy and light mesons describing strong interactions among effective meson fields as well as their couplings to electromagnetic and weak currents, including the relevant symmetry breaking terms. The effective theory includes heavy (Qq) mesons of both negative and positive parity, light pseudoscalars, as well as light vector mesons. We summarize the estimates for the parameters entering the effective lagrangian and discuss in particular some phenomenologically important couplings, such as gB * Bπ. The hyperfine splitting of heavy mesons is discussed in detail. The effective lagrangian allows for the possibility to describe consistently weak couplings of heavy (B, D) to light (π, ρ, K * , etc.) mesons. The method has however its own limitations, due to the requirement 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 γ) and flavour changing (e. g. B → K * γ) radiative decays provide another field of applications of effective lagrangians; they are discussed together with their phenomenological implications. Finally we analyze effective lagrangians describing heavy charmonium-like (QQ) mesons and their strong and electromagnetic interactions. The role of approximate heavy quark symmetries for this case and the phenomenological tests of these models are also discussed.

We introduce an effective lagrangian including negative and positive parity heavy mesons containing a heavy quark, light pseudoscalars, and light vector resonances, with their allowed interactions, using heavy quark spin-flavour symmetry, chiral symmetry, and the hidden symmetry approach for light vector resonances. On the basis of such a lagrangian, by considering the allowed weak currents and by including the contributions from the nearest unitarity poles we calculate the form factors for semileptonic decays of B and D mesons into light pseudoscalars and light vector resonances. The available data, together with some additional assumptions, allow for a set of predictions in the different semileptonic channels, which can be compared with those following from different approaches. A discussion of non-dominant terms in our approach, which attempts at including a rather complete dynamics, will however have to wait till more abundant data become available

We describe the effective heavy meson Lagrangian for S-and P-wave heavy-light mesons in terms of a model based on meson-quark interactions, where mesonic transition amplitudes are represented by diagrams with heavy mesons attached to loops containing heavy and light constituent quarks. The model is relativistic and incorporates the heavy quark symmetries. The universal form factors of the heavy meson transition amplitudes are calculated together with their slopes and compared to existing data and limits. As further applications of the model, strong and radiative decays of D* and B* are considered. The agreement with data is surprisingly good and shows that the model offers a viable alternative to effective meson Lagrangians which require a larger number of input parameters.

We perform an analysis of two-body non-leptonic decays of B and Bs mesons in the factorization approximation. We make use of the semileptonic decay amplitudes previously calculated on the basis of an effective lagrangian satisfying chiral and heavy quark symmetries and including spin 1 resonances. Exclusive semileptonic D-decay data are used as experimental input. Our results compare favorably with data, whenever they are available, and indicate a positive value for the ratio of non-leptonic coefficients a2a1, similarly to previous studies

We compute the strong coupling constant gP∗Pπ, with P and P∗ respectively pseudoscalar and vector heavy mesons by using the QCD sum rules approach. Our computation is based on the evaluation of the time ordered product of currents between the vacuum and the soft pion state. The so-called parasitic terms are taken into account and give a contribution to the sum rule of the same order of the lowest lying state, while higher dimension non perturbative terms have small numerical effects. The infinite heavy quark mass limit is also examined

We modify a chiral effective lagrangian, recently suggested to describe interactions of the light pseudoscalars with mesons containing a heavy quark, so as to incorporate light vector resonances, such as ϱ, etc. The modification uses the hidden gauge symmetry approach. As a preliminary example we present an application to the semileptonic D→K∗ decay

We compute the strong coupling constant G B * * Bπ (G D * * Dπ ), where B * * (D * * ) is the 0 + P −wave bq (cq) state, by QCD sum rules and by light-cone sum rules. The two methods give compatible results in the limit m Q → ∞, with a rather large value of the coupling constant. We apply the results to the calculation of the hadronic widths of the positive parity B and D states and to the chiral loop contribution to the ratio f Ds /f D .

We show that the reported anomalies in R b and R c can be interpreted as the effect of a heavy vector boson V universally coupled to u-and d-type quarks separately and nearly decoupled from leptons. This extra vector boson could then also naturally explain the apparent excess of the jet rate at large transverse momentum observed at CDF.