Standard model explanation of the ultrahigh energy neutrino events at IceCube

The recent observation of two PeV events at IceCube, followed by an additional 26 events between 30 and 300 TeV, has generated considerable speculations on its origin, and many exotic new physics explanations have been invoked. For a reliable interpretation, it is, however, important to first scrutinize the Standard Model (SM) expectations carefully, including the theoretical uncertainties, mainly due to the parton distribution functions. Assuming a new isotropic cosmic neutrino flux with a simple unbroken power-law spectrum, Φâ̂ E-s for the entire energy range of interest, we find that with s=1.5-2, the SM neutrino-nucleon interactions are sufficient to explain all the observed events so far, without the need for any beyond the SM explanation. With more statistics, this powerful detector could provide a unique test of the SM up to the PeV scale and lead to important clues of new physics.