A&S Graduate Studies
[PAST EVENT] Ji Liu, Physics - Oral Exam for Ph.D. Degree
Abstract: The NuMI Off-Axis Electron Neutrino Appearance (NOvA) experiment is a long baseline, off-axis neutrino oscillation experiment. It is designed to search for oscillations of muon neutrinos to electron neutrinos by comparing measurements of the NuMI beam composition in two detectors. These two detectors are functionally identical, nearly fully-active, liquid-scintillator tracking calorimeters and are located at two points along the beam line to observe the neutrinos. The Near Detector (ND), situated 1 km away from the proton target at Fermilab, measures neutrinos prior to oscillation. Then the Far Detector (FD), located 810 km away at Ash River, Minnesota, measures the neutrinos after they have traveled and potentially oscillated. The neutrino beam is generated at Fermi National Accelerator Laboratory in Batavia, Illinois by the Neutrinos at the Main Injector (NuMI) facility.
By observing the muon to electron neutrino oscillation, NOvA is capable of measuring the neutrino mass hierarchy, CP violation and the octant of mixing angle, theta_23. This thesis presents the first measurement of electron neutrino appearance in the NOvA detectors with 3.52 ? 10^20 protons-on-target (POT), data accumulated from February 2014 until May 2015. In this analysis the primary electron neutrino charged-current event selection, LID, observes 6 events in the far detector with a background prediction of 0.99 ? 0.11 (syst.), which corresponds to a 3.3 sigma excess over the no-oscillation hypothesis. This results disfavors 0.1*pi < delta_cp < 0.5*pi in the inverted mass hierarchy at 90% C.L with the reactor constraint on theta_13.
Bio: Ji Liu was born in Qiqihaer, China. She graduated from University of Science and Technology of China in Heifei, China, in June, 2009 with a Bachelor of Science degree in Physics. Later that year she started her Ph.D. education in the Physics Department of William & Mary under the supervision of Professor Patricia Vahle. Her PhD work focuses on the NOvA experiment carried out in Fermilab, Chicago. Ji moved to Houston in Spring 2016 and works as an Application Developer at Bank of America Merrill Lynch.