E1b(E-91-023)

Spokespersons

V. Burkert, D. Crabb, R. Minehart

Year

2001

Abstract

The spin structure functions g₁ for the proton and the deuteron have been measured over a wide kinematic range in x and Q² using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH₃ and ND₃ targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05 < Q² < 5 GeV² and W < 3 GeV. The first moments of g₁ for the proton and deuteron are presented – both have a negative slope at low Q², as predicted by the extended Gerasimov–Drell–Hearn sum rule. The first extraction of the generalized forward spin polarizability of the proton γ₀^p is also reported. This quantity shows strong Q² dependence at low Q². Our analysis of the Q² evolution of the first moment of g₁ shows agreement in leading order with Heavy Baryon Chiral Perturbation Theory. However, a significant discrepancy is observed between the γ₀^p data and Chiral Perturbation calculations for γ₀^p, even at the lowest Q².

Publication

1. Y. Prok, P. Bosted, V. Burkert, A. Deur, V. Dharmawardane, G. Dodge, K. Griffoen, S. Kuhn, R. Minehart and CLAS Collaboration Moments of the Spin Structure Functions g₁^p and g₁^d for 0.05 < Q² < 3.0 GeV². // Phys. Lett. B 672, 12 (2009)

Quantities

Γ₁^p_tot   Γ₁^d_meas   Γ₁^d_extrp   Γ₁^d_tot   γ₀^p_meas   γ₀^p_extrp   γ₀^p_tot   Γ₁^p_meas   Γ₁^p_extrp

Measurements