A quark model calculation of the processes [Formula Presented] and [Formula Presented] is performed. At tree level, only charged pions couple to the initial state photons and neutral pions are not expected in the final state. However, a small but significant [Formula Presented] cross section is observed. We demonstrate that this may be accounted for by a rotation in isospin space induced by final-state interactions. The resulting [Formula Presented] cross section is in good agreement with experiment, while the [Formula Presented] cross section is in qualitative agreement with the data.

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Persistent URL dx.doi.org/10.1103/PhysRevC.61.025203
Journal Physical Review C - Nuclear Physics
Blundell, H.G. (H. G.), Godfrey, S, Hay, G. (G.), & Swanson, E.S. (E. S.). (2000). A quark model calculation of γ[Formula Presented]ππ including final-state interactions. Physical Review C - Nuclear Physics, 61(2). doi:10.1103/PhysRevC.61.025203