Determination of \pi^0 meson quadrupole polarizabilities from the process \gamma\gamma -> \pi^0\pi^0

Abstract

A fit of the experimental data to the total cross section of the process \gamma\gamma->\pi^0\pi^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 \pi^0 meson have been found for the first time: (\alpha2+\beta2)_\pi^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)_\pi^0 and (\alpha2+\beta2)_\pi^0 extracted from the experimental data on the process \gamma\gamma->\pi^0\pi^0 are in good agreement with the result of calculations in the framework of these dispersion sum rules.