Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetry A2

TL;DR

This study measures the proton and deuteron spin structure functions g2 and asymmetries A2 across a broad kinematic range, confirming theoretical predictions and providing new insights into nucleon spin structure.

Contribution

It provides the first comprehensive measurements of g2 and A2 for protons and deuterons over a wide kinematic range, testing theoretical models and sum rules.

Findings

A2 values are smaller than the positivity limit.

g2 aligns with Wandzura-Wilczek twist-2 predictions.

Results for twist-3 matrix elements d2 are reported.

Abstract

We have measured the spin structure functions g2p and g2d and the virtual photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 1.0 < Q^2 < 30(GeV/c)^2 by scattering 38.8 GeV longitudinally polarized electrons from transversely polarized NH3 and 6LiD targets.The absolute value of A2 is significantly smaller than the sqrt{R} positivity limit over the measured range, while g2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements d2p, d2d and d2n. The Burkhardt-Cottingham sum rule integral - int(g2(x)dx) is reported for the range 0.02 < x < 0.8.