Reduced nuclear helicity amplitudes for deuteron electrodisintegration and other processes

TL;DR

This paper introduces a method to analyze deuteron electrodisintegration by extending reduced nuclear amplitudes to individual helicity amplitudes, enabling better predictions of observables and scaling behavior at high momentum transfers.

Contribution

It develops a novel approach to include nucleon form factors in nuclear process calculations, improving agreement with experimental data and estimating scaling onset.

Findings

Deuteron photodisintegration asymmetry $\\Sigma(90^\circ) \simeq -0.06$ matches experiment better.

The method predicts scaling behavior onset above 10 GeV$^2$ for structure function B.

Results show improved agreement with experimental data for various observables.

Abstract

We extend the original idea of reduced nuclear amplitudes to capture individual helicity amplitudes and discuss various applications to exclusive processes involving the deuteron. Specifically, we consider deuteron form factors, structure functions, tensor polarization observables, photodisintegration, and electrodisintegration. The basic premise is that nuclear processes at high momentum transfer can be approximated by tree graphs for point-like nucleons supplemented by empirical form factors for each nucleon. The latter represent the internal structure of the nucleon, and incorporate nonperturbative physics, which can allow for early onset of scaling behavior. The nucleon form factors are evaluated at the net momentum transfer experienced by the given nucleon, with use of $G_E$ for a no-flip contribution and $G_M$ for a helicity-flip contribution. Results are compared with data where available. The deuteron photodisintegration asymmetry $\Sigma$ is obtained with a value of $\Sigma(90^\circ)\simeq -0.06$, which is much closer to experiment than the value of -1 originally expected. The method also provides an estimate of the momentum transfer values required for scaling onset. We find that the deuteron structure function $B$ is a good place to look, above momentum transfers of 10 GeV$^2$.