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Title: Measurement of Muon Neutrino Disappearance with the NOvA Experiment

Abstract

The NOvA experiment consists of two functionally identical tracking calorimeter detectors which measure the neutrino energy and flavour composition of the NuMI beam at baselines of 1~km and 810~km. Measurements of neutrino oscillation parameters are extracted by comparing the neutrino energy spectrum in the far detector with predictions of the oscillated neutrino energy spectra that are made using information extracted from the near detector. Observation of muon neutrino disappearance allows NOvA to make measurements of the mass squared splitting $$\Delta m^2_{32}$$ and the mixing angle $$\theta_{23}$$. The measurement of $$\theta_{23}$$ will provide insight into the make-up of the third mass eigenstate and probe the muon-tau symmetry hypothesis that requires $$\theta_{23} = \pi/4$$. This thesis introduces three methods to improve the sensitivity of NOvA's muon neutrino disappearance analysis. First, neutrino events are separated according to an estimate of their energy resolution to distinguish well resolved events from events that are not so well resolved. Second, an optimised neutrino energy binning is implemented that uses finer binning in the region of maximum muon neutrino disappearance. Third, a hybrid selection is introduced that selects muon neutrino events with greater efficiency and purity. The combination of these improvements produces an increase in the sensitivity of the analysis equivalent to collecting 40-100\% more data across the range of possible values of $$\Delta m^2_{32}$$ and $$\sin^2\theta_{23}$$. This thesis presents new results using a 14~ktonne detector equivalent exposure of $$6.05\times 10^{20}$$~protons~on~target. A fit to the far detector data, assuming normal hierarchy, produces $$\Delta m^2_{32}=2.45^{+0.087}_{-0.079}\times10^{-3}~\text{eV}^2$$ and $$\sin^2\theta_{23}$$ in the range 0.429~-~0.593 with two statistically degenerate best fit points at 0.481 and 0.547. This measurement is consistent with maximal mixing where $$\theta_{ 23} = \pi/4$$. The data used for this thesis is 1/6 of the to! tal data that NOvA expects to collect.

Authors:
 [1]
  1. Sussex U.
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1423216
Report Number(s):
FERMILAB-THESIS-2018-05
1657884
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Vinton, Luke. Measurement of Muon Neutrino Disappearance with the NOvA Experiment. United States: N. p., 2018. Web. doi:10.2172/1423216.
Vinton, Luke. Measurement of Muon Neutrino Disappearance with the NOvA Experiment. United States. doi:10.2172/1423216.
Vinton, Luke. Mon . "Measurement of Muon Neutrino Disappearance with the NOvA Experiment". United States. doi:10.2172/1423216. https://www.osti.gov/servlets/purl/1423216.
@article{osti_1423216,
title = {Measurement of Muon Neutrino Disappearance with the NOvA Experiment},
author = {Vinton, Luke},
abstractNote = {The NOvA experiment consists of two functionally identical tracking calorimeter detectors which measure the neutrino energy and flavour composition of the NuMI beam at baselines of 1~km and 810~km. Measurements of neutrino oscillation parameters are extracted by comparing the neutrino energy spectrum in the far detector with predictions of the oscillated neutrino energy spectra that are made using information extracted from the near detector. Observation of muon neutrino disappearance allows NOvA to make measurements of the mass squared splitting $\Delta m^2_{32}$ and the mixing angle $\theta_{23}$. The measurement of $\theta_{23}$ will provide insight into the make-up of the third mass eigenstate and probe the muon-tau symmetry hypothesis that requires $\theta_{23} = \pi/4$. This thesis introduces three methods to improve the sensitivity of NOvA's muon neutrino disappearance analysis. First, neutrino events are separated according to an estimate of their energy resolution to distinguish well resolved events from events that are not so well resolved. Second, an optimised neutrino energy binning is implemented that uses finer binning in the region of maximum muon neutrino disappearance. Third, a hybrid selection is introduced that selects muon neutrino events with greater efficiency and purity. The combination of these improvements produces an increase in the sensitivity of the analysis equivalent to collecting 40-100\% more data across the range of possible values of $\Delta m^2_{32}$ and $\sin^2\theta_{23}$. This thesis presents new results using a 14~ktonne detector equivalent exposure of $6.05\times 10^{20}$~protons~on~target. A fit to the far detector data, assuming normal hierarchy, produces $\Delta m^2_{32}=2.45^{+0.087}_{-0.079}\times10^{-3}~\text{eV}^2$ and $\sin^2\theta_{23}$ in the range 0.429~-~0.593 with two statistically degenerate best fit points at 0.481 and 0.547. This measurement is consistent with maximal mixing where $\theta_{ 23} = \pi/4$. The data used for this thesis is 1/6 of the to! tal data that NOvA expects to collect.},
doi = {10.2172/1423216},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2018},
month = {Mon Jan 01 00:00:00 EST 2018}
}

Thesis/Dissertation:
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