Polarizability of the nucleon

Abstract

The status of the experimental and theoretical investigations on the polarizabilities of the nucleon is presented. This includes a confirmation of the validity of the previously introduced recommended values of the polarizabilities [1,2]. It is shown that the only meaningful approach to a prediction of the polarizabilities is obtained from the nonsubtracted dispersion theory, where the appropriate degrees of freedom taken from other precise experimental data are taken in account. The present values of the recommended polarizabilities are $\alpha_p= 12.0 \pm 0.5$, $\beta_p= 1.9 \mp 0.5$, $\alpha_n= 12.6 \pm 1.2$, $\beta_n= 2.6 \mp 1.2$ in units of $10^{-4}$fm$^3$ and $\gamma^{(p)}_\pi= -36.4 \pm 1.5$, $\gamma^{(n)}_\pi =+58.6 \pm 4.0$, $\gamma^{(p)}_0=-0.58 \pm 0.20$, $\gamma^{(n)}_0= +0.38\pm 0.22$ in units of $10^{-4}$fm$^4$.