New axion contribution to the two-photon decays of neutral pions Zhen-Yan Lu, Yang Huang, Ji-Gui Cheng, Qi Lu and Shu-Peng Wang Eur. Phys. J. C, 85 2 (2025) 207 Published online: 24 February 2025 DOI: 10.1140/epjc/s10052-025-13906-7