Measurement of the proton and deuteron spin structure functions g2 and asymmetry A2

Abstract We have measured the spin structure functions g 2 p and g 2 d and the virtual photon asymmetries A 2 p and A 2 d 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 NH 3 and 6 LiD targets. The absolute value of A 2 is significantly smaller than the R positivity limit over the measured range, while g 2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements d 2 p , d 2 d and d 2 n . The Burkhardt-Cottingham sum rule integral ∫ g 2 (x)dx is reported for the range 0.02≤ x ≤0.8.