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  • Open Access

Photon emission from weakly magnetized neutral pions

Xinyang Wang1,*, Fan Lin1,†, and Igor Shovkovy2,3,‡

  • *Contact author: wangxy@aust.edu.cn
  • †Contact author: linfan@aust.edu.cn
  • ‡Contact author: igor.shovkovy@asu.edu
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Phys. Rev. D 113, 116034 – Published 23 June, 2026

DOI: https://doi.org/10.1103/b9k3-tqyd

Abstract

Using a hadronic framework, we derive an explicit expression for photon production from neutral pions in a weak background magnetic field. Our calculation is built on the proton triangle diagram with an effective Yukawa π0-proton coupling, offering an alternative to quark-level descriptions that is advantageous when the magnetic length greatly exceeds the proton size. Corrections to the pion decay constant are computed up to second order in the magnetic-field strength, revealing that the field generally suppresses the decay rate. Quantitatively, however, the effect remains modest even for fields as strong as |eB|≃mπ2. The differential photon emission rate exhibits anisotropy, with the strongest suppression occurring when the pion momentum is perpendicular to the magnetic field. Overall, the modification of the π0→γγ rate is parametrically small, scaling as |eB|2/mP4, where mP is the proton mass. While the magnetic-field-induced anisotropy is conceptually interesting in principle, it is likely too small to be resolved in present heavy-ion measurements.

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Phys. Rev. D 113, 116034– Published 23 June, 2026
  • Received 12 December 2025
  • Accepted 21 May 2026
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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.

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