Deep Inelastic Scattering of Polarized Electrons by Polarized ${}^3$He and the Study of the Neutron Spin Structure

Abstract

The neutron longitudinal and transverse asymmetries $A_1^n$ and $A_2^n$ have been extracted from deep inelastic scattering of polarized electrons by a polarized ${}^3$He target at incident energies of 19.42, 22.66 and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions $g_1^n(x,Q^2)$ and $g_2^n(x,Q^2)$ over the range $0.03<x<0.6$ at an average $Q^2$ of 2 (GeV$/c{)}^2$. The data are used for the evaluation of the Ellis-Jaffe and Bjorken sum rules. The neutron spin structure function $g_1^n(x,Q^2)$ is small and negative within the range of our measurement, yielding an integral ${\int }_{0.03}^{0.6}{g}_1^n(x)dx=-0.028\pm 0.006(stat)\pm 0.006(syst)$. Assuming Regge behavior at low $x$, we extract ${\Gamma }_1^n={\int }_0^1{g}_1^n(x)dx=-0.031\pm 0.006(stat)\pm 0.009(syst)$. Combined with previous proton integral results from SLAC experiment E143, we find ${\Gamma }_1^p-{\Gamma }_1^n=0.160\pm 0.015$ in agreement with the Bjorken sum rule prediction ${\Gamma }_1^p-{\Gamma }_1^n=0.176\pm 0.008$ at a $Q^2$ value of 3 (GeV$/c{)}^2$ evaluated using ${\alpha }_s=0.32\pm 0.05$.

97 pages, format is postscript file