Determination of the Source Flavor Ratio of Ultrahigh Energy Neutrinos

Abstract

We discuss the reconstruction of neutrino flavor neutrino at a distant source in the very high en- ergy regime. This reconstruction procedure is relevant to the confirmation of detecting cosmogenic neutrinos, for example. To facilitate such a reconstruction, it is imperative to achieve effective flavor discriminations in terrestrial neutrino telescopes. We note that, for energies beyond few tens of PeV, a tau-lepton behaves like a track similar to a muon. Hence, while it is rather challenging to separate {\nu}{\mu} from {\nu}{\tau} in this case, one can expect to isolate {\nu}e from the rest by a distinctive shower signature. We present the result of flavor ratio reconstruction given the anticipated accuracies of flavor measurement in neutrino telescopes and current uncertainties of neutrino mixing parame- ters. It is shown that the further separation between {\nu}{\mu} and {\nu}{\tau} events does not improve the flavor reconstruction due to the approximate {\nu}{\mu} - {\nu}{\tau} symmetry.

Comments: 4 pages, 10 figures. Paper reorganized with a new title