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# First observation of PeV-energy neutrinos with IceCube

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### Abstract

We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04 $$\pm$$ 0.16 and 1.14 $$\pm$$ 0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current $$\nu_{e,\mu,\tau}$$ ($$\bar\nu_{e,\mu,\tau}$$) or charged-current $$\nu_{e}$$ ($$\bar\nu_{e}$$) interactions within the IceCube detector. The events were discovered in a search for ultra-high energy neutrinos using data corresponding to 615.9 days effective livetime. The expected number of atmospheric background is $$0.082 \pm 0.004 \text{(stat)}^{+0.041}_{-0.057} \text{(syst)}$$. The probability to observe two or more candidate events under the atmospheric background-only hypothesis is $$2.9\times10^{-3}$$ ($$2.8\sigma$$) taking into account the uncertainty on the expected number of background events. These two events could be a first indication of an astrophysical neutrino flux, the moderate significance, however, does not permit a definitive conclusion at this time.

### Author and article information

###### Journal
19 April 2013
2013-06-12
1304.5356 10.1103/PhysRevLett.111.021103