Measuring Form Factors and Structure Functions with CLAS

TL;DR

This paper discusses measurements of hadronic structure functions and form factors using the CLAS detector at Jefferson Lab, providing new high-precision data that probe quark-gluon dynamics and confinement in nucleons and nuclei.

Contribution

It reports the first high-precision measurements of the neutron magnetic form factor and the proton virtual photon asymmetry over wide kinematic ranges.

Findings

Neutron magnetic form factor measured up to Q2=4.7 GeV2 with 5-10% accuracy.

Proton asymmetry data show deviation from SU(6) symmetry and approach perturbative QCD predictions.

Results enhance understanding of nucleon structure and quark-gluon interactions.

Abstract

The physics program at the Thomas Jefferson National Accelerator Facility includes a strong effort to measure form factors and structure functions to probe the structure of hadronic matter, reveal the nature of confinement, and develop an understanding of atomic nuclei using quark-gluon degrees of freedom. The CLAS detector is a large acceptance device occupying one of the end stations. We discuss here two programs that use CLAS; measuring the magnetic form factor of the neutron and the virtual photon asymmetry of the proton. The form factor has been measured with unprecedented kinematic coverage and precision up to Q2=4.7 GeV2 and is consistent within 5%-10% of the dipole parameterization. The proton virtual photon asymmetry has been measured across a wide range in Bjorken x. The data exceed the SU(6)-symmetric quark prediction and show evidence of a smooth approach to the scaling limit prescribed by perturbative QCD.