Covariant Spectator Theory of $np$ scattering: Deuteron form factors

TL;DR

This paper calculates deuteron form factors using covariant spectator theory with high-precision fits to neutron-proton scattering data, incorporating new interaction currents and off-shell effects to improve understanding of nucleon structure.

Contribution

It introduces a new class of isoscalar $np$ interaction currents generated by the nuclear force model and demonstrates how adjusting off-shell nucleon form factors can fit scattering data and predict neutron charge form factors.

Findings

Achieved a $ ext{chi}^2$/datum $ oughly 1$ fit to all $ed$ elastic scattering data.

Predicted high $Q^2$ behavior of neutron charge form factor beyond current measurements.

Quantified the size of relativistic corrections, interaction currents, and off-shell effects.

Abstract

The deuteron form factors are calculated using two model wave functions obtained from the 2007 CST high precision fits to $np$ scattering data. Included in the calculation are a new class of isoscalar $np$ interaction currents which are automatically generated by the nuclear force model used in these fits. If the nuclear model WJC2 is used, a precision fit ($\chi^2$/datum $\eqsim1$) to the Sick Global Analysis (GA) of all $ed$ elastic scattering data can be obtained by adjusting the unknown off-shell nucleon form factors $F_3(Q^2)$ (discussed before) and $F_4(Q^2)$ (introduced in this paper), and predicting the high $Q^2$ behavior of the neutron charge form factor $G_{En}(Q^2)$ well beyond the region where it has been measured directly. Relativistic corrections, isoscalar interaction currents, and off-shell effects are defined, discussed, and their size displayed. A rationale for extending $ed$ elastic scattering measurements to higher $Q^2$ is presented.