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| Main Author: | |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2509.07191 |
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Table of Contents:
- The contribution of the electromagnetic interaction to the self-energy of pseudo-Goldstone bosons, as well as to the mixing angles and weak decay constants, is calculated in the first nonleading order in the simultaneous expansion in powers of $1/N_c$, momenta and quark masses. Particular attention is paid to the isospin symmetry breaking which is generated by means of $η$ and $η'$ admixtures to the pion. It is shown that the gluon anomaly enhances the electromagnetic contribution to the $π^0$-$η$ and $π^0$-$η'$ mixing angles, which facilitates the restoration of isospin symmetry in the spectrum of pseudo-Goldstone states at next-to-leading order. The contribution of the electromagnetic interaction to the $η$-$η'$ mixing angle is shown to be only about 3\%.