Vector mesons in the Extended Chiral Quark Model

TL;DR

This paper extends the Extended Chiral Quark Model to include vector and axial-vector channels, providing insights into low-energy QCD and supporting the existence of a heavy scalar meson around 1 GeV.

Contribution

It introduces an extended effective Lagrangian with vector and axial-vector operators, incorporating chiral symmetry constraints and large-Nc approximation for improved QCD modeling.

Findings

Supports the existence of a heavy scalar meson around 1 GeV

Determines the axial pion-quark coupling constant to be approximately 0.55 to 0.66

Provides a consistent fit of model parameters with chiral symmetry constraints

Abstract

We extend our previous formulation of low-energy QCD in terms of an effective lagrangian containing operators of dimensionality $d\le 6$ constructed with pseudoscalars and quark fields, describing physics below the scale of chiral symmetry breaking. We include in this paper the vector and axial-vector channels. We follow closely the Extended Chiral Quark Model approach and consistently work in the large-$N_c$ and leading log approximation and take into account the constraints from chiral symmetry and chiral symmetry restoration. The optimal fit of all parameters gives further support to a heavy scalar meson with a mass $\sim 1$ GeV and a value of the axial pion-quark coupling constant $g_A \simeq 0.55$ to 0.66, depending on some assumptions concerning the Weinberg sum rules.