Hadrons and Chiral Symmetry

TL;DR

This paper explores the hypothesis that high-energy hadron states exhibit effective chiral symmetry restoration, evidenced by near-degeneracy in hadron spectra, and reviews current theoretical and experimental support for this idea.

Contribution

It provides a comprehensive review of the conjecture that chiral symmetry is effectively restored in high-energy hadron states, including motivations, evidence, and alternative explanations.

Findings

Evidence of near-degenerate hadron states supports chiral symmetry restoration.

Theoretical models suggest diminishing sensitivity to chiral symmetry breaking at higher energies.

Experimental data aligns with the conjecture, but alternative explanations remain.

Abstract

These lectures discuss the question of whether a key feature is seen in hadron spectroscopy--the near degeneracy of hadrons with different parity and/or spin. It has been conjectured that this is due to an effective restoration of chiral symmetry. The conjecture is that while these states are, of course, in the symmetry-broken (Nambu-Goldstone) phase, as one goes higher in the spectrum the states become progressively less sensitive to the dynamics of chiral symmetry breaking. These lectures discuss the current status of this conjecture. The motivations for the conjecture are discussed, as is evidence--both theoretical and experimental--in its favor. Possible alternative explanations for the data are also discussed.