Observation of Seven Astrophysical Tau Neutrino Candidates with IceCube

Abstract

We report on a measurement of astrophysical tau neutrinos with 9.7 years of IceCube data. Using convolutional neural networks trained on images derived from simulated events, seven candidate ${\nu }_{\tau }$ events were found with visible energies ranging from roughly 20 TeV to 1 PeV and a median expected parent ${\nu }_{\tau }$ energy of about 200 TeV. Considering backgrounds from astrophysical and atmospheric neutrinos, and muons from ${\pi }^{\pm }/K^{\pm }$ decays in atmospheric air showers, we obtain a total estimated background of about 0.5 events, dominated by non-${\nu }_{\tau }$ astrophysical neutrinos. Thus, we rule out the absence of astrophysical ${\nu }_{\tau }$ at the $5\sigma$ level. The measured astrophysical ${\nu }_{\tau }$ flux is consistent with expectations based on previously published IceCube astrophysical neutrino flux measurements and neutrino oscillations.

Accepted for publication in Physical Review Letters. This version includes full author list metadata

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