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Searching for TeV Scale Physics in Precision Electroweak Measurements

Mon., Nov. 4, 2019 3:30 p.m. - Mon., Nov. 4, 2019 4:30 p.m.

Location: LB 235

Abstract: In analogy to their electromagnetic charge, protons and electrons carry a weak charge that describes the strength of their interactions with electroweak Z bosons. Thanks to an accidental suppression in the Standard Model of Particle Physics, these weak charges are nearly zero and therefore sensitive to unsuppressed effects from physics beyond the Standard Model. Measuring these weak charges is all but easy: their effects in elastic electron scattering are at the level of parts per billion compared to the electromagnetic interaction. Over the past decades we have perfected techniques to access the tiny effect of Z boson exchange diagrams in parity-violating electron scattering. By scattering electron beams with alternating helicity from the proton or electrons in fixed targets at Jefferson Lab, we can measure the tiny helicity asymmetries which give us access to the weak charge. We rely on precise control of beam parameters, accurate understanding of background process, and fast integrating electronics. In 2018, the Qweak experiment made the first determination of the weak charge of the proton, in agreement with Standard Model predictions. Now we are developing the MOLLER experiment which will make an ultra-precise measurement of the weak charge of the electron.