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

Abstract

The prediction of the cross section $\sigma(\gamma\gamma^*(Q^2)\to \eta\pi^0)$ based on the simultaneous description of the Belle data on the $\gamma\gamma\to \eta\pi^0$ reaction and the KLOE data on the $\phi\to\eta\pi^0\gamma$ decay is presented. The production of the scalar $a_0(980)$ and tensor $a_2(1320)$ is studied in detail. It is shown that the QCD based asymptotics of the $\gamma^*(Q^2)\gamma\to a_2(1320)\to\eta\pi^0$ 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.