Search for Sources of Astrophysical Neutrinos Using Seven Years of IceCube Cascade Events

Abstract

Low-background searches for astrophysical neutrino sources anywhere in the sky can be performed using cascade events induced by neutrinos of all flavors interacting in IceCube with energies as low as ∼1 TeV. Previously we showed that, even with just two years of data, the resulting sensitivity to sources in the southern sky is competitive with IceCube and ANTARES analyses using muon tracks induced by charge current muon neutrino interactionsespecially if the neutrino emission follows a soft energy spectrum or originates from an extended angular region.Here, we extend that work by adding five more years of data, significantly improving the cascade angular resolution, and including tests for point-like or diffuse Galactic emission to which this data set is particularly well suited. For many of the signal candidates considered, this analysis is the most sensitive of any experiment to date. No significant clustering was observed, and thus many of the resulting constraints are the most stringent to date. In this paper we will describe the improvements introduced in this analysis and discuss our results in the context of other recent work in neutrino astronomy.

Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube Neutrino Telescope

“…The observed zenith angle can be taken as the true zenith angle, θ reco z ¼ θ z , for practical purposes, since within our angular bins the difference in zenith angle between the reconstructed muon track and the MC truth is negligible (<1°, discussed in more detail in Ref. [161]).…”

Characteristics of the Diffuse Astrophysical Electron and Tau Neutrino Flux with Six Years of IceCube High Energy Cascade Data

“…The main goal of astrophysical neutrino flux measurements is a characterization of its energy dependence in a flavor dependent way and in a wide energy range [25][26][27][28][29][30][31][32], relevant for ultrahigh energy cosmic rays and QCD physics. Since the diffuse Galactic emission component, based on models of galactic particle propagation and interactions [33], is subdominant [34,35], of particular interest is the energy range ∼10-100 TeV. In this energy region, hardly accessible to muon neutrinos, several source models, including AGN cores [36,37], predict a sizable energy dependent flux.…”

“…Single cascades are electromagnetic and/or hadronic particle showers produced by (i) electron or low energy tau neutrinos scattering inelastically off target nucleons through a W boson, (ii) neutrinos of all flavors scattering inelastically off target nucleons through a Z boson, or (iii) electron antineutrinos interacting with atomic electrons to form a W − boson, the Glashow resonance [39]. Although the angular resolution of cascades is limited (> 8°) [35], their energy resolution (∼15%) [40] as well as their low atmospheric neutrino background make the cascade channel particularly well suited for measuring and characterizing the energy dependent astrophysical neutrino flux [41].…”

Zee-Burst: A New Probe of Neutrino Nonstandard Interactions at IceCube

“…For instance, the future data in all the bins may not scale proportionately to the current data and may turn out to be in better agreement with the SM prediction, thus restricting even further any room for new physics contribution. Similarly, the energy-dependent acceptance rate might improve in the future (as it did by 67% from two to seven years of data [43]), thereby increasing the effective area, and hence, the 'effective' exposure time defined here at a rate faster than linear. Finally, IceCube-Gen2 with 10 km 3 detection volume [56] is expected to go online at some point in the foreseeable future, thus increasing the total effective exposure by an order of magnitude.…”

“…For the SM interactions only, we use the publicly available flavor-dependent effective area integrated over solid angle from Ref. [5] (for 2078 days of IceCube data), along with a 67% increase in the acceptance (for 2653 days of data) [43]. In presence of non-SM interactions as in Eq.…”