[PAST EVENT] Juan Carlos Cornejo, Physics - Oral Exam for the Ph.D.

August 14, 2015
10am - 12pm
Small Hall, Room 122
300 Ukrop Way
Williamsburg, VA 23185Map this location
The Standard Model has been a theory with the greatest success in describing the fundamental interactions of particles. As of the writing of this dissertation, the Standard Model has not been shown to make a false prediction. However, the limitations of the Standard Model have long been suspected by its lack of a description of gravity, nor dark matter. Its largest challenge to date, has been the observation of neutrino oscillations, and the implication that they may not be massless, as required by the Standard Model. The growing consensus is that the Standard Model is simply a lower energy effective field theory, and that new physics lies at much higher energies.

The Qweak Experiment is testing the Electroweak theory of the Standard Model by making a precise determination of the weak charge of the proton (Qwp). Any signs of "new physics" will appear as a deviation to the Standard Model prediction. The weak charge is determined via a precise measurement of the parity-violating asymmetry of the electron-proton interaction via elastic scattering of a longitudinally polarized electron beam of an un-polarized proton target.

The experiment required that the electron beam polarization be measured to an absolute uncertainty of 1%. At this level the electron beam polarization was projected to contribute the single largest experimental uncertainty to the parity-violating asymmetry measurement.

This thesis will detail the use of Compton scattering to determine the electron beam polarization via the detection of the scattered photon. I will conclude the remainder of the dissertation with an independent analysis of the blinded Qweak.

Juan Carlos Cornejo was born in Mexico and immigrated to the United States at a young age. While living in Los Angeles he attended the California State University at Los Angeles where he began his research in the field of medium energy experimental nuclear physics. He traveled to Jefferson Lab to conduct research throughout this time and graduated with a Bachelors of Science in 2005. In 2010 he started working with Dr. Wouter Deconinck on the Qweak Experiment which uses parity-violating electron scattering to perform precision tests of the Standard Model at low energies. His dissertation focuses on using Compton scattering to determine the polarization of the longitudinally polarized electron beam.