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arXiv · hep-ph/9905420

eta -> pi^+ pi^- pi^0 gamma in Chiral Perturbation Theory

G. D'Ambrosio·G. Ecker·G. Isidori·H. Neufeld
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Abstract

We analyse the radiative decay $η\to π^+π^- π^0γ$ in the low--energy expansion of the Standard Model. We employ the notion of ``generalized bremsstrahlung'' to take full advantage of the theoretical and experimental information on the corresponding non-radiative $η\to 3 π$ decay. The direct emission amplitude of ${\cal O}(p^4)$ is due to one-loop diagrams with intermediate pions (isospin violating) and kaons (isospin conserving). The isospin conserving contributions to direct emission, including vector meson exchange appearing at ${\cal O}(p^6)$, are suppressed.

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G. D'Ambrosio, G. Ecker, G. Isidori, H. Neufeld. 1999-06-18. eta -> pi^+ pi^- pi^0 gamma in Chiral Perturbation Theory. https://doi.org/10.1016/s0370-2693(99)01144-2

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