Extracting the chiral anomaly from e + e − → 3π
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...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2025-07-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP07(2025)095 |
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| Summary: | 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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| ISSN: | 1029-8479 |