Search for the scalar $a_0$ and $f_0$ mesons in the reactions $e^+e^-\to\gamma\pi^0\pi^0(\eta)$

Abstract

It is shown that the reactions $e^+e^-\to\gamma\pi^0\pi^0(\eta)$ give a good chance for observing scalar $a_0$ and $f_0$ mesons. In the photon energy region less then 100 MeV the vector meson contributions $e^+e^-\to V^0\to\pi^0 V'^0\to\gamma\pi^0\pi^0(\eta)$ are negligible in comparison with the scalar mesons $e^+e^-\to\phi\to\gamma f_0(a_0)\to\gamma\pi^0\pi^0(\eta)$ for $BR(\phi\to\gamma f_0(a_0)\to\gamma\pi^0\pi^0(\eta))$ greater than $5\cdot10^{-6}(10^{-5})$. Using two-channel treatment of the $\pi\pi$ scattering the predictions for $BR(\phi\to\gamma (f_0+\sigma)\to\gamma\pi\pi)$ are derived. The four quark model, the model of $K\bar K$ molecule and the$s\bar s$ model of scalar $f_0$ and $a_0$ mesons are discussed.