  The IceCube Neutrino Observatory has observed a diffuse flux of astrophysical
neutrinos with energies from TeV to a few PeV. Recent IceCube analyses have
limited sensitivity to PeV neutrinos because upward-going neutrino fluxes are
attenuated by the Earth while the Extremely High Energy (EHE) result targets
cosmogenic neutrinos only above 10 PeV. In this work, we present a new event
selection that fills the gap between 1 PeV and 10 PeV. This sample is obtained
by selecting high-energy down-going through-going tracks from 8 years of data.
To reduce the atmospheric muon backgrounds and achieve a high
signal-to-background ratio, we combine two techniques. The first technique
selects events with high stochasticity because single muons created by
neutrinos lose energy more stochastically than atmospheric muon bundles whose
energy losses are smoothened due to large muon multiplicities. The second
technique uses the IceTop surface array as a veto of atmospheric background
events. To characterize the astrophysical neutrino flux and test the existence
of a cut-off in the neutrino energy spectrum at a few PeV, a global fit will be
performed by combining this sample with results from the 7-year High Energy
Starting Events (HESE) analysis.
