Multi-year search for a diffuse flux of muon neutrinos with AMANDA-II

TL;DR

This study used AMANDA-II data from 2000-2003 to search for diffuse extraterrestrial muon neutrino fluxes in the TeV-PeV range, setting the most sensitive upper limits to date without detecting a significant excess.

Contribution

It provides the first multi-year search for diffuse muon neutrinos with AMANDA-II, establishing the most stringent upper limits on the flux in the 16 TeV to 2.5 PeV range.

Findings

No excess events detected over background.

Set upper limit of 7.4 x 10^{-8} GeV cm^{-2} s^{-1} sr^{-1} for E^{-2} spectrum.

Established upper limits for various astrophysical neutrino models.

Abstract

A search for TeV - PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent livetime of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with non-thermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E^{2}\Phi_{90% C.L.} < 7.4 x 10^{-8} GeV cm^{-2} s^{-1} sr^{-1} is placed on the diffuse flux of muon neutrinos with a \Phi \propto E^{-2} spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive \Phi \propto E^{-2} diffuse astrophysical neutrino limit. We also set upper limits for astrophysical and prompt neutrino models, all of which have spectra different than \Phi \propto E^{-2}.