[PAST EVENT] Joshua Hoskins, Physics - Oral Exam for the Ph.D.

June 4, 2015
9am - 11am
Small Hall, Room 122
300 Ukrop Way
Williamsburg, VA 23185Map this location
The Qweak experiment, which completed running in May of 2012 at Jefferson Laboratory, has measured the parity-violating asymmetry in elastic electron-proton scattering at four-momentum transfer Q2=0.025 (GeV/c)2 in order to provide the first direct measurement of the protons weak charge, Qpw. The Standard Model makes firm predictions for the weak charge; deviations from the predicted value would provide strong evidence of new physics beyond the Standard Model. Using an 89% polarized electron beam at 145 uA scattering from a 34.4 cm long liquid hydrogen target, scattered electrons were detected using an array of eight fused-silica detectors placed symmetrically about the beam axis. The parity-violating asymmetry was then measured by reversing the helicity of the incoming electrons and measuring the normalized difference in rate seen in the detectors. The low Q2 enables a theoretically clean measurement; the higher order hadronic corrections are constrained using previous parity-violating electron scattering world data. The experimental method will be discussed, application of the beam modulation system to correct helicity correlated beam systematics, as well as results of extraction of the protons weak charge.

Joshua Hoskins grew up in Manchester, Kentucky. He attended Eastern Kentucky University where he received his Bachelors degree in 2006. He then continued his physics education at the College of William & Mary where he was awarded his Masters degree in 2008. Since completion of his Masters he has worked in the Experimental Nuclear group under the advisory of Prof. David Armstrong. His Ph.D. thesis deals with the measurement of the protons weak-charge using parity-violating electron scattering at Jefferson Laboratory.