Eur. Phys. J. C (2008) 56: 1-16
https://doi.org/10.1140/epjc/s10052-008-0648-9

Regular Article - Experimental Physics

Amplitude analysis of high statistics results on γγ→π⁺π^- and the two photon width of isoscalar states

¹ Institute for Particle Physics Phenomenology, Durham University, Durham, DH1 3LE, UK
² Department of Physics, Nagoya University, Nagoya, Japan
³ High Energy Research Organisation (KEK), Tsukuba, Japan
⁴ Faculty of Engineering, Kanagawa University, Yokohama, Japan

^* e-mail: m.r.pennington@durham.ac.uk

Received: 28 March 2008
Revised: 19 May 2008
Published online: 27 June 2008

Abstract

We perform an amplitude analysis of the world published data on γγ→π⁺π^- and π⁰π⁰. These are dominated in statistics by the recently published results from Belle on the charged pion channel. Nevertheless, having only limited angular information, a range of solutions remain possible. We present two solutions with Γ(f₀(980)→γγ)=0.42 and 0.10 keV, and Γ(f₂(1270)→γγ)=3.14±0.20 and 3.82 ± 0.30 keV, respectively: the former being the solution favoured by χ², the latter at the edge of acceptability. Models of the structure of the f₀(980) predict two photon widths to be between 0.2 and 0.6 keV, depending on its composition as mainly K̄K, s̄s or qq̄qq. Presently available data cannot yet distinguish unambiguously between these predictions. However, we show how forthcoming results on γγ→π⁰π⁰ can not only discriminate between, but also refine, these classes of partial wave solutions.