Light-Front Origin of Parity Doubling in High-Mass Nucleon Resonance
Agung Waluyo

Calvin Institute of Technology

Abstract

Parity doubling in highly excited baryon resonances has long been regarded as a possible signature of effective chiral symmetry restoration in nonperturbative Quantum Chromodynamics (QCD). In this work, we investigate parity-doublet structures in the high-mass Nucleon resonance and Delta baryon spectra within the mass region (1.6<M<2,5) GeV using resonance data from the Particle Data Group (PDG). Candidate parity partners are identified by requiring identical total angular momentum (J), opposite parity, and nearby resonance masses. For each pair, the parity splitting observable,
\Delta M=|M_+ - M_- |
is evaluated and analyzed as a function of the average resonance mass,
M average = (M_+ + M_-)/2
The analysis reveals several strongly degenerate nucleon parity doublets characterized by relatively small mass splittings, particularly in the intermediate excitation region around (1.7)-(1.9) GeV. In contrast, the Delta sector exhibits weaker and less systematic parity doubling, suggesting nonuniform behavior across baryon families. The observed patterns are interpreted within the framework of Light-Front Holographic QCD, where highly excited baryons are expected to experience partial suppression of spin-orbit interactions and approximate restoration of chiral symmetry. The results indicate that parity doubling emerges as an approximate and dynamically nontrivial feature of highly excited baryon spectroscopy rather than an exact universal symmetry.

Keywords: Hadron Spectroscopy, Light-Front Holographic QCD, Parity doubling, Baryon resonances, Chiral symmetry restoration

Topic: Theory, Nuclear, and Particle Physics