Ultra-high energy neutrinos with IceCube

We report on a search for ultra-high energy neutrinos with energy greater than 106GeV using the data taken with the IceCube detector at the South Pole. The data was collected between June 2010 and May 2011 when 90% of the IceCube detector was in operation and from May 2011 to May 2012 which corresponds to the first physics run with the fully completed IceCube detector. Two signal neutrino candidate events are observed in the sample of 670.1 days of livetime over expected background rates of 0.06 events. These events are consistent with the cascade-like events induced by νe charged current or νe,μ,τ neutral current interaction within the IceCube detector volume. Preliminary p-values for a background-only hypothesis are 1.6×10−3(2.9σ) without a prompt atmospheric neutrino contribution and 1.5×10−2(2.2σ) with a default perturbative QCD-based prompt neutrino contribution.