Light, Unstable Sterile Neutrinos: Phenomenology, a Search in the IceCube Experiment, and a Global Picture
Name
moulai-marjon-phd-phys-2021-thesis.pdf
Description
Thesis PDF
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14.66 MB
Format
Adobe PDF
Checksum (MD5)
220681b98ee4751c8d5bc3e3132fed23
Author(s)
Moulai, Marjon H.
Advisor(s)
Conrad, Janet M.
Date Issued
June 2021
Publisher
Massachusetts Institute of Technology
Abstract
Longstanding anomalies in neutrino oscillation experiments point to the existence of a fourth, hypothetical neutrino: the sterile neutrino. Global fits to a sterile neutrino model find a strong preference for such a model over the massive neutrino Standard Model. However, the fit results suffer from inconsistencies between datasets, referred to as tension. This motivates more complicated models for new physics. This thesis considers a model of unstable sterile neutrinos, where the heaviest mass state can decay. First, the phenomenology of unstable sterile neutrinos is explored in the IceCube experiment, a gigaton neutrino detector located at the South Pole. Second, global fits to traditional and unstable sterile neutrino models are combined with one year of data from IceCube. A preference for the unstable sterile neutrino model is found, as well as a reduction in tension. Lastly, a high statistics search for unstable sterile neutrinos is performed in IceCube. The Standard Model is rejected with a ๐-value of 2.8% and the traditional sterile neutrino model is rejected with a ๐-value of 4.9%. The best-fit point is [formula] , [formula], and ๐ยฒ = 2.5๐ ยฑ 1.5๐, where ๐ is the coupling that mediates the neutrino decay. The best-fit corresponds to a lifetime of the heaviest neutrino of ๐โ/๐โ = 6 ร 10โปยนโถ s/eV. A Bayesian analysis finds a best model with similar sterile parameters.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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