Luis Roca

Weak decays of heavy hadrons into dynamically generated resonances

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.

Hidden gauge formalism for the radiative decays of axial-vector mesons

The radiative decay of the axial-vector resonances into a pseudoscalar meson and a photon is studied using the vector meson Lagrangian obtained from the hidden gauge symmetry (HGS) formalism. The formalism is well suited to study this problem since it deals with pseudoscalar and vector mesons in a unified way, respecting chiral invariance. We show explicitly the gauge invariance of the set of diagrams that appear in the approach and evaluate the radiative decay width of the a{sub 1}(1260) and b{sub 1}(1235) axial-vector meson resonances into {pi}{gamma}. We also include the contribution of loops involving anomalous couplings and compare the results to those obtained previously within another formalism.

Two photons into π0π0

AbstractWe perform a theoretical study based on dispersion relations of the reaction γγ → π0π0 emphasizing the low-energy region. We discuss how the ƒ0(980) signal emerges in γγ → ππ within the dispersive approach and how this fixes to a large extent the phase of the isoscalar S-wave γγ → ππ amplitude above the

Scalar radius of the pion and zeros in the form factor

K\bar K

Scattering of unstable particles in a finite volume: the case of

threshold. This allows us to make sharper predictions for the cross-section at lower energies and our results could then be used to distinguish between different ππ isoscalar S-wave parameterizations with the advent of new precise data on ππ → π0π0. We compare our dispersive approach with an updated calculation employing the unitary chiral perturbation theory (UgCPT). We also pay special attention to the role played by the σ-resonance in γγ → ππ and calculate its coupling and width to γγ, for which we obtain Γ(σ → γγ) = (1.68 ± 0.15) keV.

\pi \rho

We study the behavior with the number of colors (

scattering and the

{N}_{c}

a_1(1260)

) of the two poles associated to the