Extracting the chiral anomaly from e⁺e^-→ 3π

2025/04/18 by Hoferichter, Martin, Hoid, Bai-Long, Kubis, Bastian · 2 citations
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Theory (nucl-th)

paper · doi:10.48550/arxiv.2504.13827

Abstract

The strength of the interaction of three pions and a photon, F_3π is predicted by the axial anomaly in terms of the pion decay constant, a relation that is frequently used to constrain low-energy radiative processes involving pions, but only tested experimentally at the 10% level. Here, we present a new avenue to test this prediction, via a fit of a dispersive description of the γ^*→3π amplitude to data for e⁺e^-→ 3π. From the global fit to SND, CMD-2, and BaBar data we obtain F_3π=33.1(1.7) GeV^-3, in agreement with the chiral prediction at the level of 5%. We also consider dispersive fits to the recent data by Belle II, in which case we observe tensions with the dispersive constraints, the width parameters of ω and ϕ, and the chiral anomaly.

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• Dispersion relations: foundations
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