Connection between Neutral Pion Decay and Proton Compton Scattering

The inclusion of the single-pion intermediate state significantly improves the agreement between theory and experiment for proton Compton scattering. Excitation functions and angular distributions for various assumed values of the ${\pi }^0$ lifetime are presented. On this basis one may definitely exclude ${\pi }^0$ lifetimes >${10}^{-16\mathrm{}}$ sec or <5×${10}^{-19\mathrm{}}$ sec.