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Radiative charmonium decays in a contact-interaction model with dynamical quark anomalous magnetic moment

Yehan Xu1, Zanbin Xing1, Khépani Raya2, and Lei Chang1

  • 1School of Physics, Nankai University, Tianjin 300071, China
  • 2Department of Integrated Sciences and Center for Advanced Studies in Physics, Mathematics and Computation, University of Huelva, E-21071 Huelva, Spain

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Phys. Rev. D 114, 014014 – Published 6 July, 2026

DOI: https://doi.org/10.1103/csgz-fqz6

Abstract

The BESIII Collaboration has recently reported two measurements of the two-photon decay width of the ηc meson. The 2024 result is significantly larger than most theoretical and empirical expectations, while a subsequent measurement published in early 2026 shows better agreement with the world average and conventional theoretical estimates. In this work, we study the ηc→γγ and J/ψ→γηc processes within a contact interaction model that incorporates valence-quark anomalous magnetic moment effects, which are absent in standard treatments. Besides achieving agreement with modern lattice QCD estimates for these observables, we find that the 2024 central value for ηc→γγ lies above the range that could be accommodated by the present framework, whereas the 2026 result is naturally consistent with it.

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Phys. Rev. D 114, 014014– Published 6 July, 2026
  • Received 3 May 2026
  • Accepted 9 June 2026
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