We investigate the decay of a(1)+ (1260) -> pi(+) pi(+) pi(-) with the assumption that the a(1) (1260) is dynamically generated from the coupled channel rho pi and (K) over barK* interactions. In addition to the tree level diagrams that proceed via a(1)(+) (1260) -> rho(0)pi -> pi(+) pi(+) pi(-) , we take into account also the final state interactions of pi pi -> pi pi and (K) over barK -> pi pi. We calculate the invariant pi(+) pi(-) mass distribution and also the total decay width of a(1)+ (1260) -> pi(+) pi(+) pi(-) as a function of the mass of a(1) (1260). The calculated total decay width of a(1) (1260) is significantly different from other model calculations and tied to the dynamical nature of the a(1) (1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the rho pi component in the a(1) (1260) wave function.

The N*(2120) in gamma p -> phi p and gamma p -> K+Lambda(1520) reactions were studied within the effective Lagrangian approach. It is shown that when the contribution from N*(2120) is considered, the current experimental data can indeed be described reasonablywell. We also demonstrate that the angular distributions provide direct information of these reactions, which could be useful for the investigation of the N*(2120) resonance and may be tested by future experiments.

In this paper, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.

Motivated by the experimental measurements of D-0 radiative decay modes, we have proposed a model to study the D-0 -> (K) over bar*(0)gamma decay, by establishing a link with D-0 -> (K) over bar*(0) V (V =3D rho(0), omega) decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for V gamma conversion. As a result, we have found the branching ratio B[D-0 -> (K) over bar*(0)gamma]=3D(1.55-3.44)x10(-4), which is in fair agreement with the experimental values reported by the Belle and BaBar collaborations.

We have performed a calculation of the γp → π + π − p reaction, where the two pions have been separated in D-wave producing the f 2(1270) resonance. We use elements of the local hidden gauge approach that provides the interaction of vector mesons in which the f 2(1270) resonance appears as a ρ-ρ molecular state in L = 0 and spin 2. The vector meson dominance, incorporated in the local hidden gauge approach converts a photon into a ρ 0 meson and the other meson connects the photon with the proton. The picture is simple and has no free parameters, since the parameters of the theory have been constrained in the previous study of the vector-vector states. In a second step we introduce new elements, not present in the local hidden gauge approach, adapting the ρN N propagator to Regge phenomenology and introducing the ρ tensor coupling. We find that both the differential cross section as well as the t dependence of the cross section are in good agreement with the experimental results and provide support for the molecular picture of the f 2(1270) resonance in the first baryonic reaction where it has been tested.

We investigate the decay of and with R being the , , resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of , well within the present measurable range. In order to further test the dynamical nature of these resonances we study the and decays close to the and thresholds and make predictions for the ratio of the mass distributions in these decays and the decay widths. The measurement of these decays rates can help unravel the nature of these resonances.

We have performed a calculation of the gamma(p) -> pi(+) p-p reaction, where the two pions have been separated in D-wave producing the f(2)(1270) resonance. We use elements of the local hidden gauge approach that provides the interaction of vector mesons in which the f(2)(1270) resonance appears as rho-rho. molecular state in L =3D 0 and spin 2. The vector meson dominance, incorporated in the local hidden gauge approach converts a photon into a rho(0) meson and the other meson connects the photon with the proton. The picture is simple and has no free parameters, since the parameters of the theory have been constrained in the previous study of the vector-vector states. In a second step we introduce new elements, not present in the local hidden gauge approach, adapting the rho propagator to Regge phenomenology and introducing the rho NN tensor coupling. We find that both the differential cross section as well as the t dependence of the cross section are in good agreement with the experimental results and provide support for the molecular picture of the f(2)(1270) resonance in the first baryonic reaction where it has been tested.