Lightest scalar and tensor resonances in $\gamma\gamma\to\pi\pi$ after the Belle experiment

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New high statistics Belle data on the $\gamma\gamma\to\pi^+\pi^-$ reaction cross section measured in the range of pion-pair invariant masses $\sqrt{s}$ between 0.8 GeV and 1.5 GeV are analyzed to clarify the current situation around the $\sigma(600)$, $f_0(980)$, and $f_2(1270)$ resonances in $\gamma\gamma$ collisions.

• The present analysis shows that the direct coupling constants of the $\sigma(600)$ and $f_0(980)$ resonances to $\gamma\gamma$ are small, and the $\sigma(600)\to\gamma\gamma$ and $f_0(980)\to\gamma\gamma$ decays are four-quark transitions caused by the $\pi^+\pi^-$ and $K^+K^-$ loop mechanisms, respectively.
• The chiral shielding of the $\sigma(600)$ resonance takes place in the reactions $\gamma\gamma\to\pi\pi$ as well as in $\pi\pi$ scattering.
• Some results of a simultaneous description of the $\gamma\gamma\to\pi^+\pi^-$ and $\gamma\gamma\to\pi^0\pi^0$ Belle data are also presented.