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

S. R. Beane·M. Malheiro·J. A. McGovern·D. R. Phillips·U. van Kolck
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Abstract

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) $γ$p amplitude of McGovern to experimental data in the region $ω,\sqrt{|t|} \leq 180$ MeV, obtaining a chi^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 (theory) and beta_p=3.4 +/- 1.1 (stat.) +/- 0.1 (theory), both in units of 10^{-4} fm^3. We also compute Compton scattering on deuterium to O(Q^4). The $γ$d 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 $γ$d scattering experiments with a chi^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 sizeable error bars.

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S. R. Beane, M. Malheiro, J. A. McGovern, D. R. Phillips, U. van Kolck. 2004-07-30. Compton scattering on the proton, neutron, and deuteron in chiral perturbation theory to O(Q^4). https://doi.org/10.1016/j.nuclphysa.2004.09.068

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