1/Nc approximation and universality of vector mesons

Abstract

In this work, we argue that the observed differences in the value of the vector coupling constant extracted from the decays $\ensuremath{\rho}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ (${g}_{\ensuremath{\rho}}=6.0$), $\ensuremath{\rho}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ (${g}_{\ensuremath{\rho}}=5.0$) and $\ensuremath{\omega}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ (${g}_{\ensuremath{\rho}}=5.7$), where $l=e$, $\ensuremath{\mu}$, are an indication of the important role played by the $1/{N}_{c}$ corrections in the description of these processes. We show that an emission of a photon by charged meson loops in the ${\ensuremath{\rho}}^{0},\ensuremath{\omega},\ensuremath{\phi}\ensuremath{\rightarrow}\ensuremath{\gamma}$ transitions is a key process that allows to describe above vector meson decays into two leptons with a single value ${g}_{\ensuremath{\rho}}=6.0$. Our result supports the idea of universality of neutral vector mesons and clarifies the role of accounting of $1/{N}_{c}$ corrections to its fulfilment.