Compton Scattering by the Nucleon

Abstract

The status of Compton scattering by the nucleon at energies of the first and second resonance is summarized. In addition to a general test of dispersion theories and a precise determination of polarizabilities, the validities of four fundamental sum rules are explored. {\it Recommended} averages of experimental values for the electromagnetic polarizabilities and spin-polarizabilities of the nucleon are determined: $\alpha_p=12.0\pm 0.6$, $\beta_p=1.9\mp 0.6$, $\alpha_n= 12.5 \pm 1.7$, $\beta_n= 2.7 \mp 1.8$ (unit $10^{-4}$fm$^3$), $\gamma^{(p)}_\pi= -38.7 \pm 1.8$, $\gamma^{(n)}_\pi = 58.6 \pm 4.0$ (unit $10^{-4}$fm$^4$).