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(Q4) γp amplitude of McGovern to experimental data in the region ω, t ≤ 180 MeV, obtaining a χ2 /d.o.f. of 133/113. This yields a model-independent extraction of proton polarizabilities based solely on low-energy data: αp = (12.1 ± 1.1 (stat.)) -0.5 +0.5 (theory) and βp = (3.4 ± 1.1 (stat.))-0.1 +0.1 (theory), both in units of 10-4 fm3. We also compute Compton scattering on deuterium to O(Q4). The γd 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 γd scattering experiments with a χ2 /d.o.f. = 26.6/20, and find αN = (13.0 ± 1.9 (stat.))-1.5 +3.9 (theory) and a βN that is consistent with zero within sizable error bars.
ASJC Scopus subject areas
- Nuclear and High Energy Physics