https://doi.org/10.1140/epjc/s10052-025-13807-9
Regular Article - Theoretical Physics
Isospin-breaking contribution to the model-independent axion-photon-photon coupling in U(3) chiral theory
1
Department of Physics, Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University, 050024, Shijiazhuang, China
2
Departamento de Física, Universidad de Murcia, 30071, Murcia, Spain
3
School of Physics, Southeast University, 211189, Nanjing, China
Received:
14
November
2024
Accepted:
9
January
2025
Published online:
28
January
2025
We pursue the calculation of the model-independent component of the axion-photon-photon coupling in the U(3) chiral perturbation theory up to next-to-leading order, with the emphasis on the isospin breaking effect. The mixing of the 
-
-
-axion system is revised as well by working out the complete linear isospin-breaking terms. Our calculation shows that the isospin-breaking correction to the axion-photon-photon coupling amounts to more than 15%, comparing with the result in the isospin limit.
© The Author(s) 2025
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