Magnetic polarizability of octet baryons near the physical quark-mass point
Date
2025
Authors
Kabelitz, T.
Kamleh, W.
Leinweber, D.
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Journal article
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Physical Review D, 2025; 112(1):014516-1-014516-14
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Thomas Kabelitz, Waseem Kamleh, and Derek Leinweber
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Abstract
The magnetic polarizabilities of octet baryons are examined close to the physical quark-mass point using the background-field method in lattice QCD. For the first time, quantitative evidence of a lightquark exceptional configuration problem is presented. This exploratory calculation shows how these exceptional configurations have hindered previous attempts to determine magnetic polarizabilities near the physical mass point. The origin of the exceptional configuration problem lies in the use of a Wilsontype fermion action on electroquenched gauge-field configurations, where the dynamical-fermion gaugefield generation algorithm ignores the electric charges of the quarks. Changes in the fermion determinant that would suppress some gauge fields in the background magnetic field are neglected, leaving improbable gauge fields that generate large additive mass renormalizations which manifest as significant outliers in correlation-function distributions. The nature and extent of the exceptional configuration problem is illustrated through the development of an algorithm for the systematic identification and removal of the exceptional configurations. We find the light up and down quarks to be problematic, especially the up quark with its larger electric charge. The heavier mass of the strange quark protects the hyperon correlation functions to some extent. However, these also show some change upon the removal of exceptional configurations. Upon removing exceptional configurations, we find our results to be in accord with the behavior anticipated by chiral perturbation theory. However, we emphasize that there is no first-principles justification for the removal of exceptional configurations and, in light of the severity of the problem, we recommend the alternative formalism offered through the consideration of four-point function methods.
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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.