New Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities

TL;DR

This paper presents a new measurement of deuteron Compton scattering data that refines the extraction of neutron electromagnetic polarizabilities, using advanced theoretical analysis and extending the energy range of previous experiments.

Contribution

It provides the first new data in over a decade for deuteron Compton scattering, doubling the dataset and improving the precision of neutron polarizability extraction through Chiral Effective Field Theory analysis.

Findings

Neutron electric polarizability: 11.55 +/- 1.25 (stat) +/- 0.2 (BSR) +/- 0.8 (th)

Neutron magnetic polarizability: 3.65 +/- 1.25 (stat) +/- 0.2 (BSR) +/- 0.8 (th)

Data are consistent with previous measurements and theoretical models.

Abstract

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data --- and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world dataset. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using Chiral Effective Field Theory with dynamical \Delta(1232) degrees of freedom shows the data are consistent with and within the world dataset. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities and combining them with a recent result for the proton, we obtain the neutron polarizabilities as \alpha_n = [11.55 +/- 1.25(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \beta_n = [3.65 -/+ 1.25(stat) +/- 0.2(BSR) -/+ 0.8(th)] X 10^{-4} fm3, with \chi^2 = 45.2 for 44 degrees of freedom.