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Stafford, Samuel JA Search for Ultra-high Energy Cosmic Neutrinos: Data Analysis of the Antarctic Impulsive Transient Antenna, Third Flight
Doctor of Philosophy, The Ohio State University, 2017, Physics
Ultra-high Energy (UHE) neutrinos represent an increasingly important messenger in astronomy and astrophysics. The Antarctic Impulsive Transient Antenna (ANITA) experiment campaign utilizes a balloon-borne phased antenna array to detect coherent Cherenkov radio-frequency pulses induced by UHE neutrinos interacting with the Antarctic ice. We analyzed the data from the third ANITA flight (ANITA-III) for evidence of Ultra-high energy neutrinos by augmenting interferometric methods used in analyses of previous ANITA flights. Continuous wave (CW) radio content from ground-based Antarctic habitations and orbiting geostationary communications satellites interferes with the detection and analysis of neutrino-induced radio signals; we developed circular polarization analysis methods to facilitate improved rejection of false positives induced by satellite CW. We also developed new methods of calculating signal-to-noise ratio (SNR) of event waveforms, and enhanced event localization by applying a probability distribution function (PDF) based on the measured resolution of our interferometry. We developed a final linear discriminant cut for rejecting thermal and anthropogenic signals by dividing the continent into equal-area bins and optimizing the cut to each individual bin, so as to obtain the strongest possible the upper limit on cosmic neutrino flux.

Committee:

James Beatty, PhD (Advisor); John Beacom, PhD (Committee Member); Amy Connolly, PhD (Committee Member); Richard Kass, PhD (Committee Member)

Subjects:

Astrophysics; Physics

Keywords:

neutrinos; interferometry; radio; antarctica; ANITA; antarctic impulsive transient antenna; ultra high energy neutrinos; astroparticle physics; askaryan;

Dailey, Brian TAnalysis of the second flight of the ANtarctic Impulsive Transient Antenna with a focus on filtering techniques
Doctor of Philosophy, The Ohio State University, 2017, Physics
The observed cutoff in the cosmic ray spectrum leads to a highly motivated expectation of an ultra-high energy (UHE) neutrino flux, coming from interactions between the cosmic rays and cosmic microwave background photons. Although no UHE neutrinos have yet been detected; better background separation and removal will help accelerate the search. Past flights of the ANtarctic Impulsive Transient Antenna (ANITA) experiment have set the strongest limits on the UHE neutrino flux above 10^{19} eV. Due to the advanced sensitivity of future flights to both signal and anthropogenic backgrounds, the techniques used in the past analyses may not be sufficient to remove backgrounds. Here, we discuss processes developed for this analysis. First, we discuss newly techniques to filter event waveforms in both the amplitude and phase spectra. These new techniques were applied to the ANITA-2 experiment data set. We discuss a new technique developed that uses equal area bins of ice on the Antarctic continent. Further, we define a set of analysis cuts, how the analysis cuts were optimized for maximum sensitivity for UHE neutrinos, how the number of background and neutrino events were estimated. For our search, we used the maximal Kotera et. al. 2010 flux model and optimized based on this model. After optimization, we found zero events from the 10% sample passing all cuts. These techniques will prove useful for future flights of ANITA as the sensitivity of the instrument increases. The optimization procedure can also provide a starting point for future analysis. The filtering technique shown here decreased mis-reconstruction in pointing of events. The HealPix method, while requiring further refinement, shows promise by retaining valuable areas of ice that may have been removed from previous analyses.

Committee:

Amy Connolly (Advisor); John Beacom (Committee Member); Klaus Honscheid (Committee Member); Andrew Heckler (Committee Member)

Subjects:

Physics

Keywords:

ANITA; Ultra High Energy Neutrinos; HealPix; ANITA-2 analysis; amplitude filtering; phase filtering;