Measurement of the 3He Spin-Structure Functions and of Neutron (3He) Spin-Dependent Sum Rules at 0.035<Q^2<0.24 GeV^2

Abstract

The spin-structure functions $g_1$ and $g_2$, and the spin-dependent partial cross-section ${\sigma }_{\mathrm{TT}}$ have been extracted from the polarized cross-sections differences, $\Delta {\sigma }_{\parallel }\left(\nu ,Q^2\right)$ and $\Delta {\sigma }_{\perp }\left(\nu ,Q^2\right)$ measured for the $\overrightarrow{{}^{\text{3}}\text{He}}(\vec{\text{e}},{\text{e}}^{\prime })\text{X}$ reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6${}^{\circ }$ and 9${}^{\circ }$ from a longitudinally or transversely polarized ${}^3$He target. The data cover the kinematic regions of the quasi-elastic, resonance production and beyond. From the extracted spin-structure functions, the first moments $\overline{{\Gamma }_1}\left(Q^2\right)$, ${\Gamma }_2\left(Q^2\right)$ and $I_{\mathrm{TT}}\left(Q^2\right)$ are evaluated with high precision for the neutron in the $Q^2$ range from 0.035 to 0.24~GeV${}^2$. The comparison of the data and the chiral effective field theory predictions reveals the importance of proper treatment of the $\Delta$ degree of freedom for spin observables.

7 pages, 5 figures, 3 tables. Version published in Phys. Lett. B