Exploring the Structure of the Neutron with Electron-Scattering Experiments Using Polarized Helium-3 Targets

Jaideep Singh (University of Virginia)

Laser-polarized He-3 has long been proven to be extremely useful for exploring the structure of the neutron in electron-scattering experiments. In this talk, we'll discuss the JLab Polarized Helium-3 program with a special emphasis on E97-110, an experiment designed to measure the generalized Gerasimov-Drell-Hearn (GDH) sum rule at low four-momentum transfers, Q^2. Based on modest yet robust theoretical arguments, this sum rule is a versatile and important tool for studying nucleon spin structure over the entire Q^2 range. At low Q^2 (0.03 to 0.3 (GeV/c)^2), such measurements serve to test Chiral Perturbation Theory and probe its limits of applicability. Our measurement will also provide new constraints on understanding the neutron and He-3 spin structure and a better understanding of the effect of nucleon resonances. Preliminary results will be presented. In addition, we'll also discuss recent advances in polarized He-3 targets. Using spin-exchange optical pumping (SEOP), the He-3 polarization of these high-density (10 amagats) two-chamber target cells now regularly approaches 70\%. This remarkable performance has been achieved by taking advantage of both alkali-hybrid SEOP and high-power spectrally-narrowed diode lasers. We'll share what we've learned about applying these new technologies.

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