Precision measurements of $g_1$ of the proton and the deuteron with 6 GeV electrons

TL;DR

This paper reports high-precision measurements of the polarized structure functions g1 for protons and deuterons using 6 GeV electrons, providing insights into nucleon spin structure and quark-gluon polarization.

Contribution

It presents the first high-statistics measurements of g1p and g1d over a broad kinematic range, improving constraints on nucleon spin contributions within perturbative QCD.

Findings

g1/F1 ratio nearly independent of Q^2 at fixed x

Resonant structures observed up to W=2.3 GeV

Results help constrain quark and gluon polarization and high-twist effects

Abstract

The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Significant resonant structure is apparent at values of W up to 2.3 GeV. In the framework of perturbative QCD, the high-W results can be used to better constrain the polarization of quarks and gluons in the nucleon, as well as high-twist contributions.