Nucleon Form Factors - A Jefferson Lab Perspective

TL;DR

This paper reviews how Jefferson Lab's polarization measurements have advanced understanding of proton and neutron charge and magnetization distributions through elastic electron scattering, overcoming previous measurement limitations.

Contribution

It highlights the role of polarization techniques at Jefferson Lab in revolutionizing the study of nucleon form factors and spatial structure.

Findings

Polarization measurements provided new insights into nucleon structure.

Progress in form factor measurements overcame earlier limitations.

The study connects electromagnetic form factors to quark distributions inside nucleons.

Abstract

The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.