Electron Neutrino Appearance in the NO$\nu$A Experiment

Abstract

The NuMI Off-Axis $\nu_e$ Appearance (NO$\nu$A) experiment is a long baseline, off-axis neutrino oscillation experiment. It is designed to search for oscillations of $\nu_\mu$ to $\nu_e$ 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 located at two points along the beam line to observe the neutrinos. The Near Detector (ND), situated \unit[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 Nation al Accelerator Laboratory in Batavia, Illinois by the Neutrinos at the Main Injector (NuMI) facility. \\~ By observing the $\nu_\mu\to\nu_e$ oscillation, NO$\nu$A 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 $\nu_e$ appearance in the NO$\nu$A detectors with $3.52\times10^{20}$ protons-on-target (POT) data accumulated from February 2014 till May 2015. In this analysis the primary $\nu_e$ CC particle selection LID observes 6 $\nu_e$ like events in the far detector with a background prediction of $0.99\pm0.11$ (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 constrain on $\theta_{13}$.