Gluon Excitations and Quark Chiral Symmetry in the Meson Spectrum: an Einbein Solution to the Large Degeneracy Problem of Light Mesons

TL;DR

This paper investigates the large degeneracy in light meson spectra by incorporating gluon or string degrees of freedom into quark models, aiming to explain the observed quantum number pattern in QCD.

Contribution

It introduces an einbein approach to include gluon or string effects, providing a potential explanation for the n+j degeneracy in light mesons.

Findings

Large degeneracy explained by gluon or string degrees of freedom

Proposes a new quantum number pattern n+j in meson spectra

Addresses limitations of previous confining quark models

Abstract

A large approximate degeneracy of the excited hadron spectra, appears in the light meson spectra measured at LEAR, suggesting a novel principal quantum number n+j in QCD spectra. We recently showed that the large degeneracy could not be understood with state of the art confining and chiral invariant quark models, derived in a truncated Coulomb gauge. To search for a solution to this problem, here we add the gluon or string degrees of freedom. Although independently the quarks or the gluons would lead to a 2 n +j or 2 n +l spectrum, adding them may lead to the desired n+j pattern.