Measurement of the Neutron Spin Structure Function $g_1^n$ with a Polarized ^3He Target

Abstract

Results are reported from the HERMES experiment at HERA on a measurement of the neutron spin structure function $g_1^n(x,Q^2)$ in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident on a polarized ${}^3$He internal gas target. The data cover the kinematic range $0.023<x<0.6$ and $1(GeV/c{)}^2<Q^2<15(GeV/c{)}^2$. The integral ${\int }_{0.023}^{0.6}{g}_1^n(x)dx$ evaluated at a fixed $Q^2$ of $2.5(GeV/c{)}^2$ is $-0.034\pm 0.013(stat.)\pm 0.005(syst.)$. Assuming Regge behavior at low $x$, the first moment ${\Gamma }_1^n={\int }_0^1{g}_1^n(x)dx$ is $-0.037\pm 0.013(stat.)\pm 0.005(syst.)\pm 0.006(extrapol.)$.

4 pages TEX, text available at http://www.krl.caltech.edu/preprints/OAP.html