Parity Doubling Among the Baryons

Abstract

We study the evidence for and possible origins of parity doubling among the baryons. First we explore the experimental evidence, finding a significant signal for parity doubling in the non-strange baryons, but little evidence among strange baryons. Next we discuss potential explanations for this phenomenon. Possibilities include suppression of the violation of the flavor singlet axial symmetry ($U(1{)}_A$) of QCD, which is broken by the triangle anomaly and by quark masses. A conventional Wigner-Weyl realization of the $SU(2{)}_L\times SU(2{)}_R$ chiral symmetry would also result in parity doubling. However this requires the suppression of families of \emph{chirally invariant} operators by some other dynamical mechanism. In this scenario the parity doubled states should decouple from pions. We discuss other explanations including connections to chiral invariant short distance physics motivated by large $N_c$ arguments as suggested by Shifman and others, and intrinsic deformation of relatively rigid highly excited hadrons, leading to parity doubling on the leading Regge trajectory. Finally we review the spectroscopic consequences of chiral symmetry using a formalism introduced by Weinberg, and use it to describe two baryons of opposite parity.

32 pages, 8 figures; v2 revised and expanded; submitted to Phys. Rep

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Cited by in corpus (40)

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• Restoration of chiral and $U(1{)}_A$ symmetries in excited hadrons
• Dynamical Soft-Wall AdS/QCD
• Linear square-mass trajectories of radially and orbitally excited hadrons in holographic QCD
• Highly Excited Mesons, Linear Regge Trajectories and the Pattern of the Chiral Symmetry Realization
• Thermodynamics of dense hadronic matter in a parity doublet model
• Symmetries of hadrons after unbreaking the chiral symmetry
• Study of the reaction $\gamma p\to p{\pi }^0\eta$
• Parity doubling in particle physics
• Evidence for a parity doublet Delta(1920)P_{33} and Delta(1940)D_{33}$ from γp\to pπ^0η
• Chiral Mirror-Baryon-Meson Model and Nuclear Matter beyond Mean-Field
• Chiral symmetry patterns of excited mesons with the Coulomb-like linear confinement
• Hadron Spectroscopy: Theory and Experiment
• Axial charges of N(1535) and N(1650) in lattice QCD with two flavors of dynamical quarks
• Fermion masses without symmetry breaking in two spacetime dimensions
• Chiral Symmetry Breaking on the Lattice
• Alternative experimental evidence for chiral restoration in excited baryons
• IR-improved Soft-wall AdS/QCD Model for Baryons
• On the relation between low-energy constants and resonance saturation
• The large degeneracy of excited hadrons and quark models
• Baryon Fields with U_L(3) times U_R(3) Chiral Symmetry III: Interactions with Chiral (3,3_bar)+(3_bar,3) Spinless Mesons
• Regge approach to charged-pion photoproduction at invariant energies above 2 GeV
• Evidence for a spin-quartet of nucleon resonances at 2\,GeV
• The operator product expansion does not imply parity doubling of hadrons
• Chiral restoration in excited nucleons versus SU(6)
• Chiral symmetry breaking with no bilinear condensate revisited
• Weinberg like sum rules revisited
• Delta resonances, quark models, chiral symmetry and AdS/QCD
• A holographic model for the baryon octet
• Gluon Excitations and Quark Chiral Symmetry in the Meson Spectrum: an Einbein Solution to the Large Degeneracy Problem of Light Mesons
• Hadrons and Chiral Symmetry
• Effective chiral restoration in the rho'-meson in lattice QCD
• Chiral symmetry and the properties of hadrons in the Generalised Nambu-Jona-Lasinio model
• Lattice QCD study of $g_A^{N^{\ast }{N}^{\ast }}$ with two flavors of dynamical quarks
• Constraining the Infrared Behavior of the Soft-Wall AdS/QCD Model
• Oscillator model for the relativistic fermion-boson system
• Two-flavor lattice QCD study of the axial charges of N(1535) and N(1650)
• Quartet of spin-3/2 baryons in chiral multiplet $(1,1/2)\oplus (1/2,1)$ with mirror assignment
• Relativistic oscillator model with spin for nucleon resonances