Study of the alpha-particle monopole transition form factor

TL;DR

This paper investigates the helium-4 monopole form factor by calculating transition matrix elements using advanced nuclear wave functions and includes higher-order electromagnetic contributions, achieving good agreement with experimental data.

Contribution

The study combines hyperspherical harmonic calculations with chiral effective field theory Hamiltonians and incorporates higher-order electromagnetic effects to improve form factor predictions.

Findings

Results agree fairly well with recent experimental data.

Inclusion of higher-order electromagnetic contributions improves accuracy.

Comparison with other theories highlights the robustness of the approach.

Abstract

The 4He monopole form factor is studied by computing the transition matrix element of the electromagnetic charge operator between the 4He ground-state and the p+3H and n+3He scattering states. The nuclear wave functions are calculated using the hyperspherical harmonic method, by starting from Hamiltonians including two- and three-body forces derived in chiral effective field theory. The electromagnetic charge operator retains, beyond the leading order (impulse approximation) term, also higher order contributions, as relativistic corrections and meson-exchange currents. The results for the monopole form factor are in fairly agreement with recent MAMI data. Comparison with other theoretical calculations are also provided.