AMANDA 7-Year Multipole Analysis

TL;DR

This paper presents a multipole spherical harmonics analysis of neutrino arrival directions in AMANDA-II to identify potential astrophysical signals and assess detector systematics over a 7-year period.

Contribution

It introduces a novel multipole expansion method for analyzing neutrino data and applies it to a large dataset to search for extraterrestrial neutrino sources.

Findings

No significant deviation from atmospheric neutrino background detected

Simulated astrophysical signals influence the expansion coefficients in characteristic ways

Method provides a new approach to identify potential neutrino sources

Abstract

The multipole analysis investigates the arrival directions of registered neutrino events in AMANDA-II by a spherical harmonics expansion. The expansion of the expected atmospheric neutrino distribution returns a characteristic set of expansion coefficients. This characteristic spectrum of expansion coefficients can be compared with the expansion coefficients of the experimental data. As atmospheric neutrinos are the dominant background of the search for extraterrestrial neutrinos, the agreement of experimental data and the atmospheric prediction can give evidence for physical neutrino sources or systematic uncertainties of the detector. Astrophysical neutrino signals were simulated and it was shown that they influence the expansion coefficients in a characteristic way. Those simulations are used to analyze deviations between experimental data and Monte Carlo simulations with regard to potential physical reasons. The analysis method was applied on the AMANDA-II neutrino sample measured between 2000 and 2006 and results are presented.