Quasielastic Scattering of Polarized Electrons from PolarizedHe3and Measurement of the Neutron's Form Factors

Abstract

The 3 He target polarimetry depended on a previously measured dimensionless quantity, KTO, which parametrizes the Rb-He frequency shift. A new analysis of the (unpublished) data of Ref. [18] shows that at 50°C K 0 =4.73 ±0.34, which is 22% lower than our quoted value. In order to confirm this number, we have made a more precise measurement of Ko using an entirely new method. We find Ko =4.92 ±0.15, in good agreement with the reanalysis. Combining these results gives KO =4.89 ±0.14. These experiments are being prepared for publication. The effect of the new value of KO is to increase the average 3 He polarization to 46%. Similarly, the typical initial target polarizations are increased to (50-65)%. Finally, P$, the muon polarization normalized to 100% 3 He target polarization, is decreased to /^ =0.056 ±0.006. The conclusions of our paper remain the same as this value for p£ is still a factor of -2-3 lower than predicted by the standard cascade theory. Equation (8), defining the asymmetry for quasielastic scattering, should read ^si_i_iilOi (8) Pe P3 f VR + TlL '

Optically Polarized $^3$He

“…In the double cell configuration, diffusion links the polarization produced in an optical pumping cell to the target cell via a transfer tube. The first double cell targets (Chupp et al, 1992) were employed for quasielastic scattering of polarized electrons at the Bates Linear Accelerator Center, which provided some of the first double-polarization results for determination of the neutron's electric form factor (Thompson et al, 1992). Using a few watts of laser light from a Tisapphire laser, an ≈50 cm 3 cell was polarized up to 40 % in tests and was maintained between 10 % and 27 % during the experiment.…”