1307.2215 (Martin Schumacher)

Dispersion theory of nucleon polarizabilities and outlook on chiral
effective field theory    [PDF]

Martin Schumacher

The polarizabilities of the nucleon are precisely studied and well understood due to recent experimental and theoretical work based on nonsubtracted dispersion relations. The {\it recommended} experimental values are $\alpha_p=12.0\pm 0.6$, $(12.0)$, $\beta_p=1.9\mp 0.6$, $(1.9)$, $\alpha_n=12.5\pm 1.7$, $(12.7\pm 0.9)$, $\beta_n=2.7\mp 1.8$, $(2.5\mp 0.9)$ in units of $10^{-4}$fm$^3$ and $\gamma^{(p)}_\pi=-36.4\pm 1.5$, $(-36.6)$, $\gamma^{(n)}_\pi=+58.6\pm 4.0$, $(58.3)$, $(\gamma^{(p)}_0=-0.58\pm 0.20)$, $\gamma^{(n)}_0=0.38\pm 0.22)$ in units of $10^{-4}$fm$^4$ [1]. The numbers given in parentheses are predicted values. Recently attempts to reanalyse low-energy Compton scattering data by making use of different versions of chiral effective field theory ($\chi$EFT) have led to sizable discrepancies between each other and with the {\it recommended} experimental data. An investigation is presented showing that these newly analyzed data should not be included in the {\it recommendation}.

View original: http://arxiv.org/abs/1307.2215