[PAST EVENT] Dun Zhang, Physics - Oral Exam for the Ph.D. Degree
Abstract: Neutrino interactions in the detectors of long baseline oscillation experiments are analyzed to determine the neutrino flavor and energy spectrum, allowing the neutrino mass ordering and mixing parameters to be determined. For neutrino interactions below the pion production threshold, the dominant reaction is charged current quasi-elastic (CCQE) scattering. Oscillation experiments are made of heavy nuclei so the QE process occurs on nucleons that are embedded in the nuclear environment. Predictions of the QE cross-section suffer from significant uncertainties due to our understanding of that nuclear environment and the way it is probed by the weak interaction. I have developed a new technique to reduce the inelastic background to CCQE process by identifying the "Michel electrons" produced by pions. Additionally an updated neutrino flux was used to extract the cross-section and estimates for some sources of systematic uncertainties have been improved. The measured cross-section is compared to several theoretical models and the effect that the signal definition ("CCQE" vs "CCQE-like") has on the measurement is also explored.
Bio: Dun Zhang was born in 1986 in Lianyungang, a beautiful city along the coastline of China. In 2003, he entered the University of Science and Technology of China in the neighbor province and majored in physics. He focused on the theoretical physics and enjoyed an undergraduate research project on the Quantum Game Theory. In 2007, he received his B.S. in physics and continued his graduate study in the physics Ph.D program of William & Mary. He joined the high energy research group in the summer of 2009 and conducted his research on MINERvA, a neutrino scattering experiment based at Fermilab. He developed and applied new techniques to improve the measurement on differential cross-sections to improve knowledge of neutrinos interaction processes.