Abstract
The spin structure functions of the proton and the deuteron were measured during the EG4 experiment at Jefferson Lab in 2006. Data were collected for longitudinally polarized electron scattering off longitudinally polarized NH3 and ND3 targets, for Q2 values as small as 0.012 and 0.02 GeV2, respectively, using the CEBAF Large Acceptance Spectrometer. This is the archival paper of the EG4 experiment that summarizes the previously reported results of the polarized structure functions g1, A1F1, and their moments Γ¯1, γ¯0, and ĪTT, for both the proton and the deuteron. In addition, we report on new results on the neutron g1 extracted by combining proton and deuteron data and correcting for Fermi smearing, and on the neutron moments Γ¯1, γ¯0, and ĪTT formed directly from those of the proton and the deuteron. Our data are in good agreement with the Gerasimov-Drell-Hearn sum rule for the proton, deuteron, and neutron. Furthermore, the isovector combination was formed for g1 and the Bjorken integral Γ¯1p-n, and it was compared to available theoretical predictions. All of our results, to the best of our knowledge, provide for the first time extensive tests of spin observable predictions from chiral effective field theory (χEFT) in a Q2 range commensurate with the pion mass. They motivate further improvement in χEFT calculations from other approaches such as the lattice gauge method.
| Original language | English |
|---|---|
| Article number | 035202 |
| Journal | Physical Review C |
| Volume | 111 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 2025 |
Funding
We acknowledge the outstanding efforts of the staff of the Accelerator, the Target Group, and the Physics Divisions at Jefferson Lab that made this experiment possible. This work was supported in part by the U.S. Department of Energy, the U.S. National Science Foundation, the U.S. Jeffress Memorial Trust; the United Kingdom Science and Technology Facilities Council, the Italian Istituto Nazionale di Fisica Nucleare; the French Institut National de Physique Nucléaire et de Physique des Particules, the French Centre National de la Recherche Scientifique; and the National Research Foundation of Korea. J.Z. and X.Z. are supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-SC0014434. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. We are grateful to J. M. Alarcón, A. Kotikov, R. Pasechnik, and D. Volkova for sending us the predictions from their models.