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A dispersion integral is derived that connects data on $��\to ��^+��^-��$ to the $��\to ����^*$ transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the $��$ transition form factor at the origin $b_��= (2.05 {}^{+0.22}_{-0.10})\, {\rm GeV}^{-2}$. Using an additional, plausible assumption, one finds for the corresponding slope of the $��'$ transition form factor, $b_{��'} = (1.58 {}^{+0.15}_{-0.08})\, {\rm GeV}^{-2}$. Both values are consistent with all recent data, but differ from some previous theoretical analyses., 11 pages, 3 figures, 2 tables (with extended discussion of the isoscalar contribution to the transition form factor)

These are the proceedings of the second PrimeNet Workshop, held in September 26-28, 2011, at the campus of Forschungszentrum J\"{u}lich, Germany. This workshop is part of the activities in the project "Study of Strongly Interacting Matter" (acronym HadronPhysics2), which is an integrating activity of the Seventh Framework Program of EU. This HP2 project contains several activities, one of them being the network PrimeNet having the focus on Meson Physics in Low-Energy QCD. This network is created to exchange information on experimental and theoretical ongoing activities on mainly eta and eta-prime physics at different European accelerator facilities and institutes., Comment: 149 pages, 47 contributions; Editors: D.Grzonka, B. H\"oistad, C. F. Redmer, S. Schadmand

We present a new, model-independent method to analyze radiative decays of mesons to a vector, isovector pair of pions of invariant mass square below the first significant pion-pion threshold in the vector channel. It is based on a combination of chiral perturbation theory and dispersion theory. This allows for a controlled inclusion of resonance physics without the necessity to involve vector meson dominance explicitly. As an example, the method is applied to an analysis of the reactions eta -> pi+ pi- gamma and eta'->pi+ pi- gamma., 16 pages, 4 figures