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ISSN - 01709739, Zeitschrift f�r Physik C-Particles and Fields, 1996, vol. 72, p. 221-230

A search for anomalous contribution in e+e- → π/η γ annihilations

Benayoun M., Eidelman S. I., Ivanchenko V. N.

Data on e+e- → η/π0 →collected by the Neutral Detector at Novosibirsk in a c.m. energy range up to 1.04 GeV have been studied with a purpose to single out of the scattering amplitude the triangle anomaly contribution predicted by QCD, PCAC and Chiral Theories. We show that the cross section for e+e- → π0→ exhibits no sensitivity to the π0 triangle anomaly ; instead, the cross section for e+e- → η→ shows a clear sensitivity to the value of the η triangle anomaly and the best fit corresponds to a value for the η width in good correspondence with the world average value. It is also shown that the value of the p → ηγ branching fraction is noticeably influenced by the existence of the anomaly. Finally, we give for the first time the absolute value for the hadronic phases of the vector mesons for the decay modes ηγ and π0γ. © Springer-Verlag 1996.