Search for astrophysical neutrino sources using IceCube low-energy neutrinos

• Main Author: Chen, Chujie
• Other Authors: Taboada, Ignacio, Otte, A. Nepomuk, Li, Gongjie, Bogdanović, Tamara, Vandenbroucke, Justin, Physics
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Georgia Institute of Technology 2022
• Subjects: Particle astrophysics; Neutrino astronomy; Gamma-ray bursts; Antarctic; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/1853/67285

Astrophysical neutrinos can escape from radiation-opaque regions and act as messengers, allowing us to explore some of the most extreme environments in the universe. The IceCube Neutrino Observatory is designed to observe the universe via neutrinos from deep within the Antarctic ice. More than 300 people from 56 institutions in 14 countries have formed the IceCube collaboration to work on different aspects of research using the detector. Much of the work in this thesis can be attributed to collaborators in IceCube. My original work focuses on data analysis after event selection. DeepCore, a densely instrumented sub-detector of IceCube, extends IceCube’s energy reach down to about 10 GeV, enabling the search for astrophysical transient neutrino sources. I aim to utilize a newly developed event selection and dataset for both a triggered and an untriggered all-sky search for potential astrophysical neutrino origins. For the first analysis presented in this thesis, gamma-ray bursts (GRBs) are proposed as neutrino emitters. Despite predictions for multi-GeV neutrino emission from collisions of drifting neutrons in sub-photospheric GRB emissions or particle acceleration in internal shocks, the energy range studied in this study had received little attention. I present the results of a search for tens of GeV neutrinos in coincidence with GRBs using IceCube-DeepCore. This analysis was conducted on eight years of IceCube-DeepCore data and in coincidence with 2,268 GRBs. I first look for correlations between neutrino events and GRBs using six overlapping time windows centered on the prompt phase of each GRB. These time windows range from $\pm 5$ s to $\pm 250$ s. Individual $p$-values are combined using a binomial test to look for a potential subgroup of GRBs that could be neutrino sources by identifying an excess of GRBs with $p$-values less than a certain threshold. There is no evidence of neutrino emission in either search. Fermi GBM bn140807500 is the most significant individual burst, with a $p$-value of 0.01 ...