Searching for Ultra-high Energy Neutrinos with Data from a Prototype Station of the Askaryan Radio Array

2014
164 pages
Supervisor:
Thesis: PhD
  • The Ohio State University
(2014)
  • Published: 2014

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Abstract: (OhioLink)
The observed GZK cutoff in the cosmic ray spectrum has led to a strongly motivated expectation of an ultra-high energy (UHE) neutrino flux arising from the interactions between the highest energy cosmic rays and cosmic microwave background photons. Aside from these diffuse neutrinos, UHE neutrinos are also expected to be produced in the same astrophysics sources producing the UHE cosmic rays such as Gamma-Ray Bursts (GRB) and AGNs. Here, we discuss two UHE neutrino searches using data from the Askaryan Radio Array (ARA) prototype Testbed station: one search for a diffuse neutrino flux and another for neutrinos from GRBs. Testbed data from 2011 to 2012 are used for the searches in the thesis. We discuss how we define the analysis cuts, optimize the analysis cut parameters for maximum sensitivity to UHE neutrinos, estimate the number of background and neutrino events, and set neutrino flux constraints in the UHE region (>10^17eV). We use an optimistic flux model from Kotera et. al. 2010 as our baseline model and optimize our analysis cuts for this model. The GRB neutrino search follows the same analysis technique as the diffuse neutrino flux search with some modifications. A timing constraint for each GRB reduces the estimated background dramatically and therefore we can loosen some of our analysis cuts for the GRB neutrino search. We also present detailed descriptions about tools that are used for the searches such as AraSim, a Monte-Carlo simulation that we developed, and RaySolver, a code to carry out ray tracing in ice with a depth-dependent index of refraction model. We present constraints on the neutrino flux from the ARA Testbed for diffuse neutrinos and GRB neutrinos separately. These neutrino flux constraints and analysis techniques from the Testbed will provide a benchmark for the future deep ARA stations' analyses which are expected to improve neutrino flux constraints by a factor of three or more due to differences in the design of the stations.
  • neutrino: flux
  • neutrino: interaction
  • gamma ray: burst
  • neutrino: UHE
  • cosmic radiation: UHE
  • numerical calculations: Monte Carlo
  • cosmic radiation: energy
  • cosmic radiation: spectrum
  • cosmic radiation: energy spectrum
  • background