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 $f_2(1270)$.

Comments: 16 pages, four figures (POSTSCRIPT)