Precision Moller polarimetry for PREX-2 and CREX

The PREX-2 and CREX experiments in Hall A at Jefferson Lab are precision measurements of parity violating elastic electron scattering from complex nuclei. One requirement was that the incident electron beam polarization, typically approximate to 90%, be known with 1% precision. We commissioned and operated a Moller polarimeter on the beam line that exceeds this requirement, achieving a precision of 0.89% for PREX-2, and 0.85% for CREX. The uncertainty is purely systematic, accumulated from several different sources, but dominated by our knowledge of the target polarization. Our analysis also demonstrates the need for accurate atomic wave functions in order to correct for the Levchuk Effect. We describe the details of the polarimeter operation and analysis, as well as (for CREX) a comparison to results from a different polarimeter based on Compton scattering.

Automated summary

The PREX-2 and CREX experiments are precision measurements of parity violating elastic electron scattering from complex nuclei. The accurate knowledge of the incident electron beam polarization is crucial for these experiments. A Moller polarimeter was used to exceed the required precision of 1%. These measurements are important for understanding theoretical and experimental aspects of nuclear physics.