Hydrogen like classification for light nonstrange mesons

TL;DR

This paper proposes a classification scheme for light nonstrange mesons based on a symmetry group combining flavor, isospin, and a hydrogen-like O(4) symmetry, explaining observed degeneracies.

Contribution

It introduces a new symmetry-based classification model for meson spectra, emphasizing the role of a hydrogen-like O(4) symmetry distinct from chiral symmetry restoration.

Findings

Degeneracy pattern explained by $SU(2)_f\times I\times O(4)$ symmetry

Distinction from chiral symmetry restoration clarified

Implications for meson spectrum classification

Abstract

The recent experimental results on the spectrum of highly excited light nonstrange mesons are known to reveal a high degree of degeneracy among different groups of states. We revise some suggestions about the nature of the phenomenon and put the relevant ideas into the final shape. The full group of approximate mass degeneracies is argued to be $SU(2)_f\times I\times O(4)$, where $I$ is the degeneracy of isosinglets and isotriplets and O(4) is the degeneracy group of the relativistic hydrogen atom. We discuss the dynamical origin and consequences of considered symmetry with a special emphasis on distinctions of this symmetry from the so-called chiral symmetry restoration scenario.