Strange Vector Form Factors from Parity-Violating Electron Scattering

TL;DR

This paper reviews experimental efforts at Jefferson Lab to measure strange quark contributions to nucleon structure via parity-violating electron scattering, providing insights into the role of strange quarks in nucleon form factors.

Contribution

It summarizes the techniques and results of major Jefferson Lab experiments (HAPPEX and G0) on strange form factors and discusses their implications in QCD.

Findings

Evidence of strange quark contributions to nucleon form factors.

Successful measurement of parity-violating asymmetries.

Insights into the role of strange quarks in nucleon structure.

Abstract

The simplest models might describe the nucleon as 3 light quarks, but this description would be incomplete without inclusion of the sea of glue and q-qbar pairs which binds it. Early indications of a particularly large contribution from strange quarks in this sea to the spin and mass of the nucleon motivated an experimental program examining the role of these strange quarks in the nucleon vector form factors. The strangeness form factors can be extracted from the well-studied electromagnetic structure of the nucleon using parity-violation in electron-nuclear scattering to isolate the effect of the weak interaction. With high luminosity and polarization, and a very stable beam due to its superconducting RF cavities, CEBAF at Jefferson Lab is a precision instrument uniquely well suited to the challenge of measurements of the small parity-violating asymmetries. The techniques and results of the two major Jefferson Lab experimental efforts in parity-violation studies, HAPPEX and G0, as well as efforts to describe the strange form factors in QCD, will be reviewed.