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arXiv · 2601.22902

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

Michał Marczenko·Krzysztof Redlich
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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 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 $T_H \simeq 323~$MeV, 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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Michał Marczenko, Krzysztof Redlich. 2026-01-30. Evidence for quark-diquark structure of baryons from fluctuations of conserved charges. https://doi.org/10.1103/yb26-gj61

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