Hadrons and Chiral Symmetry

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.

Lectures originally given at the 2009 Schladming Winter School, "Fundamental Challenges of QCD". A version of these lecture notes will appear in Nucl. Phys. B (Proc. Suppl.)

References in corpus (11)

• Restoration of chiral and $U(1{)}_A$ symmetries in excited hadrons
• I = 0 C = +1 mesons from 1920 to 2410 MeV
• Partial wave analysis of pbar-p annihilation channels in flight with I=1, C=+1
• Light meson spectrum and classical symmetries of QCD
• Parity doubling in particle physics
• Combined analysis of meson channels with I=1, C = -1 from 1940 to 2410 MeV
• Parity Doubling Among the Baryons
• I=0, C=-1 mesons from 1940 to 2410 MeV
• Alternative experimental evidence for chiral restoration in excited baryons
• Effective restoration of chiral symmetry in excited mesons
• The operator product expansion does not imply parity doubling of hadrons

Cited by in corpus (5)

• Influence of the axial anomaly on the decay $N(1535)\to N\eta$
• Effective chiral restoration in the rho'-meson in lattice QCD
• Some indication for a missing chiral partner eta_4 around 2 GeV
• A multiquark approach to excited hadrons and Regge trajectories
• The flavor universality of some mass splittings in hadrons