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  • Open Access

Evidence for quark-diquark structure of baryons from fluctuations of conserved charges

Michał Marczenko1,2,* and Krzysztof Redlich1,3,†

  • 1Institute of Theoretical Physics, University of Wrocław, plac Maksa Borna 9, PL-50204 Wrocław, Poland
  • 2International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8531, Japan
  • 3Polish Academy of Sciences PAN, Podwale 75, PL-50449 Wrocław, Poland

  • *Contact author: michal.marczenko@uwr.edu.pl
  • †Contact author: krzysztof.redlich@uwr.edu.pl
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Phys. Rev. C 114, 025205 – Published 28 August, 2026

DOI: https://doi.org/10.1103/yb26-gj61

Abstract

We study fluctuations and correlations of conserved charges in QCD using a string-based description of the hadronic mass spectrum. Mesons and baryons are modeled as open relativistic strings with quark-antiquark and quark-diquark endpoints, respectively, leading to an exponential Hagedorn growth of states with a limiting temperature fixed by the string tension. We find that continuous Hagedorn spectra constrained by experimentally established hadrons underestimate net-baryon number fluctuations obtained in lattice QCD (LQCD) calculations. By extracting the Hagedorn string spectrum directly from lattice QCD through a fit to the second-order net-baryon number susceptibility, we obtain a consistent description of a broad set of fluctuations of conserved charges from LQCD with the Hagedorn temperature TH≃323MeV, without introducing additional free parameters. Our results provide thermodynamic evidence in support of a string quark-diquark picture of baryons in the confined phase of QCD.

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Phys. Rev. C 114, 025205– Published 28 August, 2026
  • Received 6 February 2026
  • Accepted 12 August 2026
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