Speaker
Description
A M\o ller polarimeter has been active in Hall A at Jefferson Lab since the late 1990s. During the first decade of its use, it was limited to systematic errors of several percent due to its use of a low field tilted foil target whose polarization was the limiting uncertainty. Eventually, an upgrade in the target and measurement techniques allowed for uncertainties down to the 2\% level. Two further upgrades to the target in 2010 and 2015 allowed for achievement of saturation polarization of the foil along the beam direction further reducing this systematic error and introducing an era of sub-percent level M\o ller polarimetry. This trajectory of increased precision is continuing with the approval of the MOLLER experiment and the proposal of the PVDIS experiment in Hall A initiating a program to reach <0.5\% uncertainty. The plan is to utilize the current apparatus with a few small upgrades, requiring a precise understanding of the spectrometer optics, validated models of Levchuk and radiative corrections and a careful examination of all contributions to the systematic uncertainty with an eye to minimizing each one. Key systematic errors under investigation are target polarization, DAQ dead time and accidental corrections and uncertainties arising from potential polarization differences between low and high current. I will discuss the plans to achieve this aggressive goal and the current status of those efforts.
