  An experiment on the radiative pi^+ meson photoproduction from the proton
(gamma p->gamma pi^+ n) was carried out at the Mainz Microtron MAMI in the
kinematic region 537 MeV <E_{gamma}<817 MeV,
140^o<theta_{gamma-gamma'}^cm<180^o. The pi^+ meson polarizabilities have been
determined from a comparison of the data with the predictions of two different
theoretical models, the first one being based on an effective pole model with
pseudoscalar coupling while the second one is based on diagrams describing both
resonant and nonresonant contributions. The validity of the models has been
verified by comparing the predictions with the present experimental data in the
kinematic region where the pion polarizability contribution is negligible
(s_1<5 mu^2) and where the difference between the predictions of the two models
does not exceed 3%. In the region, where the pion polarizability contribution
is substantial (5<s_1/mu^2<15, -12<t/mu^2<-2), the difference
(alpha-beta)_{pi^+} of the electric (alpha) and the magnetic (beta)
polarizabilities has been determined. As a result we find:
(alpha-beta)_{pi^+}=(11.6\pm 1.5_{stat}\pm 3.0_{syst}\pm 0.5_{mod})x10^-4fm^3.
This result is at variance with recent calculations in the framework of chiral
perturbation theory.
