Dispersive analysis for η→γγ ⋆

C. Hanhart; A. Kupść; U.-G. Meißner; F. Stollenwerk; A. Wirzba

doi:10.1140/epjc/s10052-013-2668-3

2022 Impact factor 4.4

Particles and Fields

This article has an erratum: [https://doi.org/10.1140/epjc/s10052-015-3429-2]

Eur. Phys. J. C (2013) 73: 2668
https://doi.org/10.1140/epjc/s10052-013-2668-3

Regular Article - Theoretical Physics

Dispersive analysis for η→γγ ^⋆

C. Hanhart¹^,2^,3, A. Kupść⁴^,5, U.-G. Meißner¹^,2^,3^,6^,7, F. Stollenwerk¹ and A. Wirzba¹^,2^,3^*

¹ Institut für Kernphysik (Theorie), Forschungszentrum Jülich, 52425, Jülich, Germany
² Institute for Advanced Simulation, Forschungszentrum Jülich, 52425, Jülich, Germany
³ Jülich Center for Hadron Physics, Forschungszentrum Jülich, 52425, Jülich, Germany
⁴ Division of Nuclear Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
⁵ High Energy Physics Department, National Centre for Nuclear Research, ul. Hoza 69, 00-681, Warsaw, Poland
⁶ Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, 53115, Bonn, Germany
⁷ Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany
⁸ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany

^* e-mail: a.wirzba@fz-juelich.de

Received: 24 July 2013
Revised: 15 November 2013
Published online: 11 December 2013

Abstract

A dispersion integral is derived that connects data on η→π ⁺ π ⁻ γ to the η→γγ ^∗ transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the η transition form factor at the origin . Using an additional, plausible assumption, one finds for the corresponding slope of the η′ transition form factor, . Both values are consistent with all recent data, but differ from some previous theoretical analyses.