Amplitude Analysis of High Statistics Results on $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ and the Two Photon Width of Isoscalar States

Abstract

We perform an Amplitude Analysis of the world published data on $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ and ${\pi }^0{\pi }^0$. 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 $\Gamma (f_0(980)\to \gamma \gamma )=0.42$ and 0.10 keV, and $\Gamma (f_2(1270)\to \gamma \gamma )=3.14\pm 0.20$ and $3.82\pm 0.30$ keV, respectively: the former being the solution favoured by ${\chi }^2$, the latter at the edge of acceptability. Models of the structure of the $f_0(980)$ predict two photon widths to be between 0.2 and 0.6 keV, depending on its composition as mainly $\bar{K}K$, $\bar{s}s$ or $\overline{qq}qq$. Presently available data cannot yet distinguish unambiguously between these predictions. However, we show how forthcoming results on $\gamma \gamma \to {\pi }^0{\pi }^0$ can not only discriminate between, but also refine, these classes of partial wave solutions.

34 pages, 23 figures. Version with minor changes to be published in European Journal of Physics C

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Cited by in corpus (24)

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• Two photon couplings of the lightest isoscalars from BELLE data
• f0(980) meson as a K bar K molecule in a phenomenological Lagrangian approach
• Dispersion relations for ${\gamma }^{\ast }{\gamma }^{\ast }\to \pi \pi$: helicity amplitudes, subtractions, and anomalous thresholds
• Two photons into π^0π^0
• Gluonium nature of the sigma/f_0(600) from its coupling to KK
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• Sum rules for light-by-light scattering
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• Light scalar mesons in QCD
• Comment on "Two-photon decay of the sigma meson"
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• The role of meson exchanges in light-by-light scattering
• Two-current transition amplitudes with two-body final states
• Electromagnetic trace anomaly in a generalized linear sigma model
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• Obtaining sigma --> gamma gamma Width from Nucleon Polarizabilities
• Reply to comment on "Two-photon decay of the sigma meson"
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• Low-mass scalar production in $\gamma \gamma$ scattering
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