Compton scattering on the proton, neutron, and deuteron in chiral perturbation theory to O(Q(4))

摘要

We study Compton scattering in systems with A = 1 and 2 using chiral perturbation theory up to fourth order. For the proton we fit the two undetermined parameters in the O(Q(4)) gammap amplitude of McGovern to experimental data in the region omega,root less than or equal to 180 MeV, obtaining a x(2)/d.o.f. of 133/113. This yields a model-independent extraction of proton polarizabilities based solely on low-energy data: alpha(p) = (12.1 +/- 1.1(stat.)) (+0.5)(-0.5)(theory) and beta(p) = (3.4 +/- 1.1(stat.)) (+0.1)(-0.1) (theory), both in units of 10(-4) fm(3). We also compute Compton scattering on deuterium to O(Q(4)). The gammad amplitude is a sum of one- and two-nucleon mechanisms, and contains two undetermined parameters, which are related to the isoscalar nucleon polarizabilities. We fit data points from three recent gammad scattering experiments with a x(2)/d.o.f. = 26.6/20, and find alpha(N) = (13.0 +/- 1.9 (stat.)) (+3.9)(-1.5) (theory) and a beta(N) that is consistent with zero within sizable error bars. (C) 2004 Elsevier B.V. All rights reserved.