The decay $\rho^{0}\to \pi^{0}\pi^{0}\gamma$ and the role of $\sigma$-meson

We study the radiative $\rho$, $\omega$ and $\phi$ decay into $\pi^0 \pi^0 \gamma$ and $\pi^0 \eta \gamma $ taking into account mechanisms in which there are two sequential vector-vector-pseudoscalar or axial-vector--vector--pseudoscalar steps followed by the coupling of a vector meson to the photon, considering the final state interaction of the two mesons. Other mechanisms in which two kaons are produced through the same sequential mechanisms or from vector meson decay into...

We discuss the importance of the background in order to understand the scattering in the J^{PC}=0^{++} low and intermediate energy region and in particular regarding the \sigma meson. In order to appreciate better its importance we compare with the \rho meson in the P-wave \pi\pi scattering. We also point out that in present analyses of three-body heavy meson decays, like those of D^+ and B, the role of this background is still not properly settled although it happens to be c...

In this talk we report on two physical processes, the photoproduction of $\rho$ mesons in nuclei and the $\pi^0 \pi^0$ photoproduction in nuclei at low energies. In the first case the aim is to observe experimentally the theoretically predicted changes on the $\rho $ properties in the nuclear medium. In the second case one wishes to investigate the modifications of the $\pi \pi$ interaction in the nuclear medium in the region of the $\sigma$ meson. In the first case we obse...

In the framework of the relativistic and gauge invariant spectral integral technique, we calculate radiative decays rho(770)-> gamma pi(140) and omega(780)-> gamma pi(140) supposing all mesons (pi, rho and omega) to be quark-antiquark states. The q anti-q wave functions found for mesons and photon lead to a reasonably good description of data ($\Gamma^{(exp)}_{\rho^{\pm} \to\gamma\pi^{\pm}}=68\pm 30$ keV, $\Gamma^{(exp)}_{\rho^{0}\to\gamma\pi^0}=77\pm 28$ keV, $\Gamma^{(exp)}...

A model for the two-pion photoproduction on the nucleon proposedearlier is modified to simultaneously explain the total cross sections and the invariant mass spectra. Using this model, we discuss the role of the $\rho $ meson in the $\gamma N \to \pi \pi N$ reaction.

We examine the radiative omega pi0etagamma and rho pi0etagamma decays in a phenomenological framework. We consider the VMD mechanism, chiral loops, intermediate a0-meson and rho−omega mixing. We find the values of the decay width coming from the different amplitudes and compare the results with other studies. We observe that a0-meson intermediate state is very important in the case of the rho pi0etagamma decay and small in the other case for which VMD contribution is do...

The study of the pi^- p -> rho^0 n and pi^- p -> omega n amplitudes close and below the vector meson production threshold (1.2< sqrt(s) <1.8 GeV) reveals a rich dynamics arising from the presence of specific baryon resonances in this energy range. The interference pattern of the e^+e^- decays of the rho^0 and omega mesons produced in pi^- p reactions reflects directly this dynamics. We discuss this interference pattern in the pi^- p -> e^+e^- n reaction as function of the tot...

Isospin violating mixing of \rho- and \omega-mesons is reconsidered in terms of propagators. Its influence on various pairs of (\rho^0,\omega)-decays to the same final states is demonstrated. Some of them, (\rho^0,\omega)\to\pi^+\pi^- and (\rho^0,\omega)\to\pi^0\gamma, have been earlier discussed in the literature, others (e.g., (\rho^0,\omega)\to\eta\gamma and (\rho^0,\omega)\to e^+e^-) are new in this context. Changes in partial widths for all the decay pairs are shown to b...

In order to assess the relevance of chiral dynamics in the scalar sector we address two recent problems: radiative decay of the $\phi$, for which there are quite recent data from Frascati, and the modification of the $\sigma$ properties in the nuclear medium seen through the $\pi^0 \pi^0$ photoproduction in nuclei.

The interference of the $\rho^0$ and $\omega$ mesons has been studied in the hadronic and leptonic decay channels, i.e., dipion and dilepton decay channels respectively, but this interference is not studied yet in the semihadronic or semileptonic decay channel, e.g., $V \to \pi^0\gamma$. $V$ denotes either $\rho^0$ or $\omega$ meson. To look for the quoted interference in the $\pi^0\gamma$ decay channel as well as the contribution of $\rho$ meson to the cross section, the cor...