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Linear realization of an SU(3) parity doublet model for octet baryons with a bad diquark

Bikai Gao1,* and Atsushi Hosaka1,2,†

  • *Contact author: bikai@rcnp.osaka-u.ac.jp
  • †Contact author: hosaka@rcnp.osaka-u.ac.jp
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Phys. Rev. D 113, 036008 – Published 6 February, 2026

DOI: https://doi.org/10.1103/s39n-mlw2

Abstract

We construct a linear SU(3)L×SU(3)R parity doublet model for octet baryons. Our model employs the (3,3¯)+(3¯,3) and (3,6)+(6,3) chiral representations while excluding the (8,1)+(1,8) representation. Through systematic analysis, we demonstrate that the (3,6)+(6,3) representation containing symmetric “bad” diquarks, despite being energetically disfavored, is essential for reproducing the correct baryon mass hierarchy—particularly the Σ−Ξ mass ordering. The model incorporates both spontaneous and explicit chiral symmetry breaking, with the latter implemented through bare quark mass terms that properly account for SU(3) flavor breaking effects. Our numerical analysis successfully reproduces the ground-state octet baryon masses and predicts the spectrum of excited states up to 2.5 GeV. For the experimentally challenging Ξ sector, we identify Ξ(1950) as the first positive-parity excitation. The analysis reveals that ground states are dominated by the (3,3¯)+(3¯,3) representation, consistent with the preference for “good” diquark configurations, while the (3,6)+(6,3) contribution remains crucial for the mass spectrum.

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Phys. Rev. D 113, 036008– Published 6 February, 2026
  • Received 30 October 2025
  • Accepted 13 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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