Another look at the angular distributions of the $\gamma\gamma\to\pi \pi$ reactions

Abstract

We analyze the existing data on the angular distributions of the $\gamma\gamma\to \pi^+ \pi^- ,\pi^0 \pi^0$ reactions with using of the unitary model for helicity 2 amplitude. The purpose is to obtain the D--wave parameters and S--wave cross section. We obtain from experiment in the first time the values of $\alpha + \beta$ for sum of the electric and magnetic pion's polarizabilities. We found the S-wave cross sections much smaller as compared with previous similar analysis. Comparison of the $\gamma\gamma\to \pi^+ \pi^-$ and $\gamma\gamma\to \pi^0 \pi^0$ data gives an indication for a marked I = 2, J = 2 contribution in region of $f_2(1270)$.