Compton scattering on the proton, neutron, and deuteron in chiral perturbation theory to image Original Research Article

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 View the MathML source, obtaining a χ2/d.o.f. of 133/113. This yields a model-independent extraction of proton polarizabilities based solely on low-energy data: View the MathML source and View the MathML source, 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 View the MathML source and a βN that is consistent with zero within sizable error bars.