About the inclusion of an infinite number of resonances in anomalous decays

Abstract

The extracted value for the $g^{eff}_{\omega \rho\pi}$ effective coupling from experimental data, considering only the $\rho$ meson, resumes not only the $\rho$ meson effect but also all its additional radial excitation modes. By explicitly adding the radial excitations of the $\rho$ meson, considering a particular form of the spectrum and relations among the couplings, we identify the single $g_{\omega \rho \pi}$ and the $\rho$ radial excitations effect in the $\omega \rightarrow \pi^0 \gamma$ decay. We obtain that the individual coupling is in the range $g_{\omega\rho\pi}= 8.2 - 8.6 {\text GeV}^{-1}$, which is about 40% smaller than the effective $g^{eff}_{\omega\rho\pi}$. We verify the consistency with the chiral approach in the $\pi^0 \rightarrow \gamma\gamma$ and $\gamma^* \rightarrow 3\pi$ processes. Besides the model dependence, our description succeeds in exhibiting how each contribution came into the game. In particular, we show that for the $\gamma^* \rightarrow 3 \pi$ decay, the usual relation $\mathcal{A}^{VMD}_{\gamma3\pi}=(3/2)\mathcal{A}^{WZW}_{\gamma3\pi}$, encodes all the vector contributions and not only the $\rho$ meson one. In addition, we find that there is an almost exact (accidental) cancelation between the radial excitations and the contact term contributions.