Probing Cosmic Ray Anisotropy with Atmospheric Neutrinos
In the hundred years that have followed the discovery of cosmic rays, more about them remains unknown than known. Many concerted efforts are currently underway to detect cosmic rays using a variety of detection methods in space, on the surface of Earth, and deep underground. Of the many remaining my...
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| Language: | English |
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Drexel University
2020
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| Online Access: | https://dx.doi.org/10.17918/d8vq1s https://na04.alma.exlibrisgroup.com/discovery/fulldisplay/alma991014632194504721/01DRXU_INST:ResearchRepository |
| Summary: | In the hundred years that have followed the discovery of cosmic rays, more about them remains unknown than known. Many concerted efforts are currently underway to detect cosmic rays using a variety of detection methods in space, on the surface of Earth, and deep underground. Of the many remaining mysteries, the one addressed in this work is the anisotropy in arrival directions of the cosmic rays incident on the atmosphere. This behaviour has been observed in both hemispheres of the planet, at high significance, from 1 TeV - 1 EeV energy ranges, at angular scales from 5 degrees to 180 degrees, and displays no time variation. It is measured consistently as a 0.1% over- and under-fluctuation. This work presents the first neutrino analysis of cosmic ray arrival directions so far, specifically, in the northern hemisphere. The analysis is done with an atmospheric neutrino dataset which was specifically designed for this analysis and composed of neutrinos detected by the IceCube South Pole Neutrino Observatory from 2011-2016. The goal of the search was to detect cosmic ray anisotropy as observed in atmospheric muons, but this time, in atmospheric neutrinos. To this end, a new atmospheric neutrino dataset was created using machine learning, aiming to increase data acceptance rates by optimizing sacrifices in purity and angular acceptance. The standard analysis techniques were carried out, along with a new log-likelihood method developed to improve sensitivity in a lower-statistics realm. While no signal was detected in this analysis, the analysis methodology has been developed and tested. We project that with a total of twelve years of IceCube data will be required to be sensitive to a dipole anisotropy at the level previously reported by the Tibet-ASĪ³ Collaboration. Detection of cosmic ray anisotropy in the neutrino channel would allow for verification of known cosmic ray shower physics, and particle propagation. The neutrinos could allow us to probe the anisotropy in a new way. If the signal deviates, there could be new physics to discover. The method and data selection are developed, and in several years, new developments will be made towards unraveling the mystery of cosmic ray anisotropy with neutrinos. |
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