Constraints on ultra-high-energy cosmic ray sources from a search for neutrinos above 10 PeV with IceCube

Understand

We report constraints on the sources of ultra-high-energy cosmic ray (UHECR) above $10^{9}$ GeV, based on an analysis of seven years of IceCube data.

• This analysis efficiently selects very high energy neutrino-induced events which have deposited energies from $\sim 10^6$ GeV to above $10^{11}$ GeV.
• Two neutrino-induced events with an estimated deposited energy of $(2.6 \pm 0.3) \times 10^6$ GeV, the highest neutrino energies observed so far, and $(7.7 \pm 2.0) \times 10^5$ GeV were detected.
• The atmospheric background-only hypothesis of detecting these events is rejected at 3.6$\sigma$.