$1/N_c$ approximation and universality of vector mesons

TL;DR

This paper investigates the role of 1/Nc corrections in vector meson decays, demonstrating that including meson loop photon emissions explains decay constant discrepancies and supports the universality of neutral vector mesons.

Contribution

It introduces a model accounting for 1/Nc corrections via meson loops, unifying decay constants of vector mesons and confirming their universality.

Findings

Photon emission by charged meson loops explains decay constant differences.

A single universal coupling value describes vector meson decays into leptons.

Inclusion of 1/Nc corrections aligns theoretical predictions with experimental data.

Abstract

In this work, we argue that the observed differences in the value of the vector coupling constant extracted from the decays $\rho\to \pi\pi$ ($g_{\rho} = 6.0$), $\rho\to l^+l^-$ ($g_{\rho} = 5.0 $) and $\omega\to l^+ l^-$ ($g_{\rho} = 5.7$), where $l=e,\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 $\rho^0, \omega,\phi\to\gamma$ transitions is a key process that allows to describe above vector meson decays into two leptons with a single value $g_\rho = 6.0$. 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.