Search for the sources of the astrophysical high-energy muon-neutrino flux with the IceCube neutrino observatory
- Publikationstyp:
- Dissertation
- Metadaten:
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- Abstract
- Cosmic rays have been measured for more than a century, however, their sources and their acceleration process are still a major open questions in astroparticle physics. Ideal messenger particles and a smoking gun signal for this hadronic acceleration are neutrinos. With the observation of an high-energy astrophysical neutrino flux in 2013 and the confirmation in the independent detection channel of high-energy through-going muon-neutrinos, the IceCube Neutrino Observatory opened a new window to the non-thermal universe. In this thesis we search for point-like sources of the observed astrophysical high-energy muon-neutrino flux. The search is based on a high statistic and high purity data sample taken by the IceCube Neutrino Observatory and contains data from eight years of livetime. The event selection focus on well-reconstructed, up- and through-going muon neutrino events, which are reconstructed with a median angular resolution of ∼1∘ at 1 TeV energy and ∼0.3∘ at 1 PeV energy. An unbinned likelihood method is used to test celestial positions for the existence of a point-like source. The likelihood method is optimized to sources showing similar characteristics as the observed astrophysical high-energy muon-neutrino flux. The sensitivity on the muon-neutrino flux of a point-like source with an E−2 spectrum is of the order of E2dN/dE=3⋅10−13TeVcm−2s−1 and improves by about ∼35% compared to previous published analyses. We perform a scan of the full Northern Hemisphere to search for a point-like source any where in the sky. As this test suffers from the large number of tested positions, in addition, sky positions from a pre-defined source list, motivated by gamma-ray observations, are tested to reduce the number of trials. Both test results are non significant and compatible with only background. We also test for neutrino emission from the source position of the blazar TXS 0506+056 for which a gamma-ray flare has been found in spatial and temporal coincidence with a extreme-high-energy neutrino alert by IceCube. This test results in a p-value of 2.93% and thus is still compatible with only background. As no test for a single point-like source shows a significant deviation from background only, we also test for the existence of a population of sub-threshold sources, both using the results from the northern sky scan and the source list. Therefore, we set up a population analysis, which tests for an excess of small but non significant p-values. Also these tests for populations of sources show no significant excess above only background. Thus, exclusion limits are calculated on the flux normalisation for sources following a baseline E−2 spectrum and source spectra found in the literature. In addition, also exclusion limits are calculated on populations of neutrino sources in dependence of their effective neutrino luminosity and effective source density. We conclude that rare but strong sources, such as BL Lacs and FSRQs, are challenged by the non observation as a significant excess in the population analysis.
- Autoren
- René Reimann
- Presented at
- RWTH Aachen University
- Datum der Veröffentlichung
- 2019
- Herausgeber URL
- https://publications.rwth-aachen.de/record/773297
- Datum der Datenerfassung
- 2020
- Thesis type
- PhD Thesis
- Titel
- Search for the sources of the astrophysical high-energy muon-neutrino flux with the IceCube neutrino observatory
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