[PAST EVENT] Siyuan Yang, Physics - Oral Exam for the Ph.D.

May 6, 2016
1pm - 4pm
Small Hall, Room 122
300 Ukrop Way
Williamsburg, VA 23185Map this location
Abstract: The Standard Model of particle physics represents our present best understanding of the elementary particles and three of the four fundamental forces. One of the most important and challenging tasks of modern particle physics is to test, and perhaps, to find the evidence for new physics not contained in the Standard Model. One such test, the Qweak experiment, was conducted at JLab in Newport News, VA, from 2010 to 2012. The goal of the experiment is to measure the value of the weak charge of proton, Qweak to a 4% precision, which, if it confirms the Standard Model prediction, will provide tighter constraints on new physics; or, if it is in disagreement with that prediction, will provide clear evidence for new physics. In this experiment, an 85% polarized electron beam with 150 ?A current is used on a 35cm thick hydrogen target to make elastic electron-proton scattering happen at a four-momentum transfer Q2 = 0.03GeV /c2. To determine the weak charge, we must also precisely determine the kinematics of the scattering process, namely, the Q2. In order to reach this goal, the hardware, a particle tracking system and special analysis software, the Qweak Tracking Reconstruction software, are both needed. In this dissertation, a full description of the tracking software and the prelimary analysis of the Q2 and the first subset of production data will be given. The proton?s weak charge QP was measured to be 0.064 ? 0.012, which is consistent with the prediction of the Standard Model.

Bio: Siyuan Yang was born in Chongqing, China. He graduated from University of Science and Technology of China in Heifei, China, in June, 2006 with a Bachelor of Science degree in Physics. In August 2006, he started his Ph.D. education in the Physics Department of William & Mary under the supervision of Professor David Armstrong. His Ph.D. work focuses on the Qweak experiment carried out in JLab. Siyuan moved to Houston in August 2012 and worked as a seismic imager at CGG, a French geoscience company.