The effects of explicit chiral symmetry breaking multiquark interactions on the spin 0 and 1 meson nonets: the ruling of the vector mesons

TL;DR

This paper extends a generalized NJL model to include explicit chiral symmetry breaking multiquark interactions, successfully describing the mass spectra of low-lying scalar, pseudoscalar, vector, and axial-vector mesons with high accuracy.

Contribution

It introduces a method for diagonalizing mixing terms in the NJL Lagrangian that preserves symmetries and relates meson masses to constituent quark masses, improving spectral fits.

Findings

Accurately fits the four low-lying meson spectra

Derives a mass relation involving vector and axial-vector mesons

Demonstrates the importance of explicit symmetry breaking interactions

Abstract

We have recently extended the scalar-pseudoscalar sector of a generalized NJL Lagrangian that includes all NLO non derivative interactions in Nc counting (including explicit symmetry breaking ones) in order to incorporate the spin 1 mesons in the low-lying ground state of QCD [1]. Upon bosonization, the well known mixing of the scalar-vector and of the pseudoscalar- axial-vector fields occurs in the quadratic part of the Lagrangian. We show that a linearized diagonalization of these terms can be effected in a completely general way without compromising the underlying symmetries of the Lagrangian [2]. The resulting spin 1 mass spectra evidence a relation involving only the vector and axial-vector meson masses and the constituent quark masses. We discuss the dominant role of this relation in the fits and we show that the model may be fitted to accommodate to a very good accuracy the 4 low-lying meson spectra.