Q^2 Evolution of the Neutron Spin Structure Moments using a He-3 Target

Abstract

We have measured the spin structure functions $g_1$ and $g_2$ of ${}^3$He in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.07 GeV off a polarized ${}^3$He target at a 15.5${}^{\circ }$ scattering angle. Excitation energies covered the resonance and the onset of the deep inelastic regions. We have determined for the first time the $Q^2$ evolution of ${\Gamma }_1(Q^2)={\int }_0^1{g}_1(x,Q^2)dx$, ${\Gamma }_2(Q^2)={\int }_0^1{g}_2(x,Q^2)dx$ and $d_2(Q^2)={\int }_0^1{x}^2[2g_1(x,Q^2)+3g_2(x,Q^2)]dx$ for the neutron in the range 0.1 GeV${}^2$ $\le Q^2\le$ 0.9 GeV${}^2$ with good precision. ${\Gamma }_1(Q^2)$ displays a smooth variation from high to low $Q^2$. The Burkhardt-Cottingham sum rule holds within uncertainties and $d_2$ is non-zero over the measured range.

5 pages, 2 figures, submitted to Phys. Rev. Lett.. Updated Hermes data in Fig. 2 (top panel) and their corresponding reference. Updated the low x extrapolation error Fig. 2 (middle panel). Corrected references to ChiPT calculations