Nuclear Quasi-Elastic Electron Scattering Limits Nucleon Off-Mass Shell Properties

TL;DR

This paper demonstrates that quasi-elastic electron scattering constrains models of off-shell nucleon form factors, impacting their contribution to the Lamb shift and potentially informing the proton radius puzzle.

Contribution

It introduces constraints on off-shell nucleon form factors from electron scattering data, linking nuclear physics to the proton radius puzzle.

Findings

Quasi-elastic scattering limits off-shell form factor strength.

Models can be consistent with conservation laws and low-energy theorems.

Off-shell contributions to the Lamb shift are small.

Abstract

The use of quasi-elastic electron nucleus scattering is shown to provide significant constraints on models of the proton electromagnetic form factor of off-shell nucleons. Such models can be constructed to be consistent with constraints from current conservation and low-energy theorems, while also providing a contribution to the Lamb shift that might potentially resolve the proton radius puzzle in muonic hydrogen. However, observations of quasi-elastic scattering limit the overall strength of the off-shell form factors to values that correspond to small contributions to the Lamb shift.