First estimates of the $(α+ β)^π$ from two--photon experiments

Abstract

We carry out the semi--model analysis of existing data on the angular distributions of the $γγ\rightarrowπ^+ π^- ,\ π^0 π^0$ reactions with purpose to obtain S-wave cross section and D-wave's parameters. In the first time we obtain from experiment the sum of electrical and magnetic pion polarizabilities: $(α+ β)^{π^+} = 0.28 \pm 0.07$ (MARK-II \cite{M2}), \ \ $(α+ β)^{π^+} = 0.38 \pm 0.05$ (CELLO \cite{CELLO}), \ \ $(α+ β)^{π^0} = 1.26 \pm 0.06$ (Crystal Ball \cite{CB}) \ \ in units of $10^{-42} \ cm^3$ ($e^2=4 πα$).