Electron Detectors for High Precision Compton Polarimetry in Parity Violating Electron Scattering using HVMAPS

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At Jefferson Laboratory, North America's premiere electron scattering laboratory, parity-violating electron scattering (PVES) experiments are measuring quantities with extreme precision in order to determine nuclear and nucleon properties and even to test our most basic understanding of matter - the Standard Model of Particles and Interactions. In order to make highly precise measurements you need to do two things - make many measurements of the same thing and make sure that the error on each measurement is small. The first is related to the statistical uncertainty of an experiment, the second to the systematic uncertainty. Advances in computing technology have made it possible for nuclear and particle physics experimenters to record and digitize their data, and to take many millions of samples. This allows us to measure quantities with such precision that we can make measurements of quantities on the order of parts per billion and smaller. One of the most important sources of systematic uncertainty for PVES measurements is the magnitude of the polarization of the electron beam. The polarization has to be measured very precisely and cross-checked with different methods. One method is to use a Compton polarimeter to measure the known asymmetry in Compton scattering of the polarized electron beam with polarized laser light. The benefit of doing this is that it is non-invasive - so few electrons interact with the laser light that the measurement can be made continuously without interfering with the electron beam that goes on to be used in the main experiment. There are also multiple ways that the polarization can be measured in this case - by measuring the Compton scattered electrons or photons. In order to keep up with the requirements of the experiments, the Compton polarimeter in Hall A of Jefferson Lab requires a major upgrade. It is getting upgrades to its laser, beamline, data acquisition, and its photon and electron detectors. Canadian physicists at the Universities of Manitoba and Winnipeg will be responsible for the electron detector, so that the Compton polarimeter will be able to meet the needs of the future PVES program at Jefferson Lab - forging the way into the Precision Frontier.