Constraints on neutrino oscillation parameters with the NOvA experiment

Abstract

NOvA is a long-baseline neutrino oscillation experiment, which consists of two finely-segmented liquid-scintillator detectors operating 14 mrad off-axis from the NuMI muon neutrino beam. With an 810 km baseline, the combined measurements of muon neutrino disappearance and electron neutrino appearance allow the determination of neutrino oscillation unknowns, namely the mass hierarchy, the octant of the largest neutrino mixing angle, and the CP violating phase. In this dissertation I present the joint analysis of ν µ → ν µ and ν µ → ν e oscillation data with an exposure of 8.85 × 10 20 protons on target on the 14 kton detector. It includes the estimation of neutrino energy distributions in the far detector using near detector data constraints, details of the implementation of the simultaneous fit of ν µ and ν e samples, and the effect of systematic uncertainties on the measurement of oscillation parameters. I also discuss NOvA's projected sensitivity to determine the mass hierarchy and discover CP violation in future analyses with increased exposure and the addition of antineutrino datasets. With 66 electron neutrino and 126 muon neutrino candidates, the best fit to the data corresponds to the normal mass hierarchy, ∆m 2 32 =2.44×10 −3 eV 2 /c 4 , sin 2 θ 23 = 0.56, and δ CP = 1.21π, with the allowed regions ∆m 2 32 ∈ [2.37, 2.52] × 10 −3 eV 2 /c 4 , sin 2 θ 23 ∈ [0.43, 0.51] ∪ [0.52, 0.60] and δ CP ∈ [0, 0.12π] ∪ [0.91π, 2π] at the 68.3% C.L. Our data disfavor maximal mixing by 0.8σ, δ CP = π/2 in the inverted hierarchy at higher than 3σ, and the entire inverted mass hierarchy at the 95% confidence level. By increasing the size of the samples and adding anti-neutrino data, NOvA can potentially resolve the neutrino mass hierarchy at 4σ C.L. or higher for some combinations of oscillation parameters. Improvements to the sensitivity to the determination of the mass hierarchy and CP violation in the neutrino sector can be achieved through gains in the NuMI beam intensity, the inclusion of external data, and refinements in the analysis methodology.

Toward A Precision Era Of Neutrino Oscillation Physics: Liquid Argon Scintillation Detector Development for DUNE and Neutrino Oscillation Studies with NOvA

“…The contributors to the intrinsic beam ν e (ν e ) background at the FD is shown on the bottom left, where it is noted that both pion-and kaon-produced electron (anti-)neutrinos contribute to the signal between 1 and 4GeV [58]. This decomposition method has been discussed elsewhere, for example Reference [56]. Further, the spectrum of identified Michel electrons in data and simulation is given in the bottom right [59].…”

“…Contained and uncontained muon neutrino candidates in the ND are used to constrain the flux based on its parent (π, K, etc. )[56]. Electron(anti-)neutrinos in the beam from both pion and kaon parents are important.…”

Measurement of Long Baseline Neutrino Oscillations and Improvements from Deep Learning

“…This method uses truth information from ND selected ν µ CC events, specifically, whether they come from kaon or pion decay, in order to estimate the ν e backgrounds coming from the NuMI beam [93].…”

Measurement of the Kaon Production Normalization in the NuMI Target Using Uncontained Charged-Current Muon Neutrino Interactions in the NOvA Far Detector

“…In an even smaller fraction are the backgrounds due to tau charged-current interactions and muon antineutrinos. The total background selected in the Near Detector is broken down into NC, beam ν e CC, and ν µ CC components, using a data driven approach [50]. They are broken independently since each of them gets affected differently by oscillations.…”

“…By measuring the data/MC ratio of the selected uncontained events at the Far Detector we expect to have a constraint in the uncertainty of the kaon normalization scale. Previous works used Near Detector data [110,50,172] to give an estimate of the kaon component for the ν e -appearance analysis. But the nalysis here described uses Far Detector data for the first time.…”