Comparative study of the scalar- and tensor-meson production in the reaction $\gamma {\gamma }^{\ast }(Q^2)\to \eta {\pi }^0$

The prediction of the cross section $\sigma(\gamma\gamma^*(Q^2)\to \eta\pi^0)$basedonthesimultaneousdescriptionoftheBelledataonthe$\gamma\gamma\to \eta\pi^0$reactionandtheKLOEdataonthe$\phi\to\eta\pi^0\gamma$decayispresented\mathrm{.}Theproductionofthescalar$a_0(980)$andtensor$a_2(1320)$ is studied in detail. It is shown that the QCD based asymptotics of the ${\gamma }^{\ast }(Q^2)\gamma \to a_2(1320)\to \eta {\pi }^0$ cross section can be reached by the compensation of the contributions of $\rho (770)$ and $\omega (782)$ with the contributions of their radial excitations in $Q^2$ channel. At large $Q^2$ the $a_2(1320)$ contribution is expected to be dominant, while at $Q^2=0$ it is similar to the scalars contribution.