Some indication for a missing chiral partner eta_4 around 2 GeV

TL;DR

This paper suggests the existence of a missing high-spin meson state around 2 GeV, supporting the idea of chiral symmetry restoration in high-lying light mesons, based on reanalysis of experimental data.

Contribution

It provides evidence for a missing $4^{-+}$ meson state near 2 GeV, indicating potential chiral partner states and calling for further experimental verification.

Findings

Indication of a $4^{-+}$ state around 2 GeV from data reanalysis

Support for effective chiral symmetry restoration in high-lying mesons

Necessity for further experimental searches for missing states

Abstract

The high-lying mesons in the light quark sector previously obtained from the partial wave analysis of the proton-antiproton annihilation in flight at 1.9 - 2.4 GeV region at CERN reveal a very high degree of degeneracy. This degeneracy can be explained as due to an effective restoration of both SU(2)_L * SU(2)_R and U(1)_A symmetries combined with a principal quantum number n + J. In this case there must be chiral partners for the highest spin states in the 2 and 2.3 GeV bands presently missing in the data. Here we reanalyze the Crystal Barrel data and show an indication for existence of the missing $4^{-+}$ state around 2 GeV. This result calls for further experimental search of the missing states both in the proton-antiproton annihilation and in the production reactions.