Precision measurements of the astrophysical neutrino flux

Author / Creator

Schneider, Austin William, author

Available as

Online

Physical

Summary

The IceCube neutrino observatory has established the existence of a high-energy all-sky neutrino flux of astrophysical origin. This discovery was made using events interacting within a fiducial reg...

The IceCube neutrino observatory has established the existence of a high-energy all-sky neutrino flux of astrophysical origin. This discovery was made using events interacting within a fiducial region of the detector surrounded by an active veto with reconstructed energy above 60 TeV, commonly known as the high-energy starting event sample or HESE. This work revisits the HESE sample analysis with an additional 4.5 years of data, newer glacial ice models, and improved systematics treatment. In addition to updating the data, this analysis seeks to validate previous measurements and explore all possible avenues that may have been overlooked. This work reports on the latest astrophysical neutrino flux measurements and presents a source search for astrophysical neutrinos. The compatibility of these observations with specific isotropic flux models proposed in the literature and generic power-law-like scenarios are explored. It is found that the astrophysical neutrino spectrum, when assumed equal for neutrinos and anti-neutrinos and among neutrino flavors, is compatible with an unbroken power law, with a preferred spectral index of 2.87[+0.20][-0.19] for the 68.3 % confidence interval. The techniques developed here will prove useful in the next generation of analyses, as more data is incorporated. These include a new approach to accounting for simulation statistical uncertainties in counting experiments and an improved method of computing the veto suppression effects on atmospheric neutrinos.

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