The Spin Structure Function g_2

摘要

We have measured the spin structure functions g_2~p and g_2~d over the kinematic range 0.02 ≤ x < 0.8 and 0.7 < Q~2 < 20 GeV~2 by scattering 29.1 and 32.3 GeV longitudinally polarized electrons from transversely polarized NH_3 and ~6LiD targets. Our measured g_2 approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3 reduced matrix elements d_2~p and d_2~n are less than two standard deviations from zero. The data are inconsistent with the Burkhardt-Cottingham sum rule. The Efremov-Leader-Teryaev integral is consistent with zero within our measured kinematic range.