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arXiv · 1412.5385

Analysis of the J/psi --> pi^0 gamma^* transition form factor

Bastian Kubis·Franz Niecknig
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Abstract

In view of the first measurement of the branching fraction for J/psi --> pi^0 e^+ e^- by the BESIII collaboration, we analyze what can be learnt on the corresponding transition form factor using dispersion theory. We show that light-quark degrees of freedom dominate the spectral function, in particular two-pion intermediate states. Estimating the effects of multi-pion states as well as charmonium, we arrive at a prediction for the complete form factor that should be scrutinized experimentally in the future.

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Bastian Kubis, Franz Niecknig. 2015-02-25. Analysis of the J/psi --> pi^0 gamma^* transition form factor. https://doi.org/10.1103/physrevd.91.036004

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