Determination of π^0 meson quadrupole polarizabilities from the process γγ-> π^0π^0

Abstract

A fit of the experimental data to the total cross section of the process γγ->π^0π^0 in the energy region from 270 to 2250 MeV has been carried out using dispersion relations for the invariant amplitudes where the quadrupole polarizabilities are free parameters. As a result the sum and difference of the electric and magnetic quadrupole polarizabilities of the π^0 meson have been found for the first time: (\alpha2+\beta2)_π^0=(-0.181+-0.004)*10^{-4}fm^5, (\alpha2-\beta2)_pi^0=(39.70+-0.02)*10^{-4}fm^5. In addition, dispersion sum rules have been constructed for this sum and difference, respectively. The values of (\alpha2-\beta2)_π^0 and (\alpha2+\beta2)_π^0 extracted from the experimental data on the process γγ->π^0π^0 are in good agreement with the result of calculations in the framework of these dispersion sum rules.