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arXiv · 1504.06505

Insights into $Q^2 \bar{Q}^2$ states from an effective perspective

Ll. Ametller·P. Talavera
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Abstract

We discuss the two photon coupling of the lightest scalar meson on the basis of an extension of $\chi$PT. Using low energy data on the pion form-factor and the $\gamma\gamma\to \pi^+\pi^-(\pi^0\pi^0)$ cross-sections as inputs, we find $\Gamma(\sigma\to\gamma\gamma) \cong 0.126~\rm{keV} $. The smallness of the result and the relative weight between its components, ${\Gamma_{\gamma\gamma\to S_1}\over \Gamma{ \gamma\gamma\to\pi\pi\to S_1}} < 1$, suggests that the scalar $0^{++}$ meson is mainly a $Q^2\bar{Q}^2$ state.

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Ll. Ametller, P. Talavera. 2015-04-24. Insights into $Q^2 \bar{Q}^2$ states from an effective perspective. https://doi.org/10.1103/physrevd.92.074008

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