Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
2 results
Search Results
Item Measurement of Atmospheric Neutrino Oscillation Parameters Using Three Years of IceCube-DeepCore Data(2018) Cheung, Yee Lam Elim Elim; Sullivan, Gregory; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The story of neutrinos began in 1930 when Pauli proposed a hypothesized particle as a ``desperate remedy" to rescue quantum theory. Although Pauli was pessimistic about the detectability of his new particle, Reins and Cowan first discovered (anti) neutrinos in 1956. Soon after, neutrinos became a puzzle for particle physicists due to a persistent deficit in observed rates by multiple experiments. This mystery was partly answered by Pontecorvo who first proposed the idea of neutrino oscillations in 1957. In 1998, the Super-Kamiokande (SK) collaboration provided the first definitive evidence of neutrino oscillations, for which both the SK and the Sudbury Neutrino Observatory (SNO) collaborations were awarded the Nobel Prize in Physics 2015. While measuring oscillation parameters has long been a focus for numerous neutrino experiments, the IceCube Neutrino Observatory with DeepCore provides a unique window to measure atmospheric oscillation parameters. With an effective volume $\sim$ 300 times larger than SK, DeepCore can detect atmospheric neutrinos between a few and 100 GeV. In addition, IceCube acts as a thick veto shield for DeepCore to better identify atmospheric muon backgrounds. Given that the amplitude of atmospheric neutrino oscillations is expected to be maximal at $\sim$ 25 GeV, IceCube-DeepCore is well suited for studying atmospheric neutrino oscillations by probing this energy window for the first time. Using three years of IceCube-DeepCore data from 2012 to 2014, this work measures atmospheric neutrino oscillation parameters from the disappearance of muon neutrinos. The standard three neutrino mixing and matter effect due to Earth are considered. Under the assumption of a unitary mixing matrix, a binned analysis using a modified $\chi^2$ is performed, and sixteen systematics are taken into account. Preferring a normal neutrino mass ordering, this analysis measures the mass squared difference, $\Delta$m$^2_{23} = 2.55^{+0.12}_{-0.11} \times 10^{-3}$ eV$^2$, and the mixing angle, sin$^2 \theta_{23} = 0.58^{+0.04}_{-0.13}$. The measurement from this work is comparable to the latest measurements from other long baseline neutrino experiments.Item Search for Quantum Gravity with IceCube and High Energy Atmospheric Neutrinos(2010) Huelsnitz, Warren; Hoffman, Kara; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)IceCube is a cubic-kilometer neutrino telescope nearing completion in the South Pole Ice. Designed to detect astrophysical neutrinos from 100 GeV to about an EeV, it will contribute to the fields of high energy astrophysics, particle physics, and neutrino physics. This analysis looks at the flux of atmospheric neutrinos detected by IceCube while it operated in a partially-completed, 40-string configuration, from April 2008 to May 2009. From this data set, a sample of about 20,000 up-going atmospheric muon neutrino events with negligible background was extracted using Boosted Decision Trees. A discrete Fourier transform method was used to constrain a directional asymmetry in right ascension. Constraints on certain interaction coefficients from the Standard Model Extension were improved by three orders of magnitude, relative to prior experiments. The event sample was also used to unfold the atmospheric neutrino spectrum at its point of origin, and seasonal and systematic variations in the atmospheric muon neutrino flux were studied. A likelihood method was developed to constrain perturbations to the energy and zenith angle dependence of the atmospheric muon neutrino flux that could be due to Lorentz-violating oscillations or decoherence of neutrino flavor. Such deviations could be a signature of quantum gravity in the neutrino sector. The impact of systematic uncertainties in the neutrino flux and in the detector response on such a likelihood analysis were examined. Systematic uncertainties that need to be reduced in order to use a two-dimensional likelihood analysis to constrain phenomenological models for Lorentz or CPT violating neutrino oscillations were identified.