Properties of the light scalar mesons face the experimental data on the $\varphi \to {\pi }^0{\pi }^0\gamma$ decay and the $\pi \pi$ scattering

Abstract

The high-statistical KLOE data on the $\varphi \to {\pi }^0{\pi }^0\gamma$ decay are described simultaneously with the data on $\pi \pi$ scattering and the $\pi \pi \to K\bar{K}$ reaction. The description is carried out taking into account the chiral shielding of the putative $\sigma (600)$ meson and it's mixing with the well-established $f_0(980)$ meson. It is shown that the data don't contradict the existence of the $\sigma (600)$ meson and yield evidence in favor of the four-quark nature of the $\sigma (600)$ and $f_0(980)$ mesons.

Comments: A few typos are removed. 1) In Eq. (19) D_\rho(m_{\rho}) and D_\rho(m^*_{\rho}) are replaced by D_\rho(\tilde{m}_{\rho}) and D_\rho(\tilde{m}^*_{\rho}), respectively. 2) For Fit 7 in Table II the constant g_{\sigma\pi^+\pi^-}= -2.1 GeV is replaced by g_{\sigma\pi^+\pi^-}=2.1 GeV