Covariant Spectator Theory of np scattering: Deuteron Quadrupole Moment

TL;DR

This paper calculates the deuteron quadrupole moment using covariant spectator theory with high-precision np scattering data, showing that models with small P-state components can accurately predict this observable.

Contribution

It introduces a new class of isoscalar np interaction currents generated by the nuclear force model and compares two CST models with different P-state components.

Findings

Model WJC-1 underpredicts by 2.5%

Model WJC-2 agrees within 1%

Results are comparable to chiral EFT predictions

Abstract

The deuteron quadrupole moment is calculated using two CST model wave functions obtained from the 2007 high precision fits to $np$ scattering data. Included in the calculation are a new class of isoscalar $np$ interaction currents automatically generated by the nuclear force model used in these fits. The prediction for model WJC-1, with larger relativistic P-state components, is 2.5% smaller that the experimental result, in common with the inability of models prior to 2014 to predict this important quantity. However, model WJC-2, with very small P-state components, gives agreement to better than 1%, similar to the results obtained recently from $\chi$EFT predictions to order N$^3$LO.