Towards Determination of the Initial Flavor Composition of Ultrahigh-energy Neutrino Fluxes with Neutrino Telescopes

Abstract

We propose a simple but useful parametrization of the flavor composition of ultrahigh-energy neutrino fluxes produced from distant astrophysical sources: ${\varphi }_e^{}:{\varphi }_{\mu }^{}:{\varphi }_{\tau }^{}={\sin }^2\xi {\cos }^2\zeta :{\cos }^2\xi {\cos }^2\zeta :{\sin }^2\zeta$. We show that it is possible to determine or constrain $\xi$ and $\zeta$ by observing two independent neutrino flux ratios at the second-generation neutrino telescopes, provided three neutrino mixing angles and the Dirac CP-violating phase have been well measured in neutrino oscillations. Any deviation of $\zeta$ from zero will signify the existence of cosmic ${\nu }_{\tau }^{}$ and ${\bar{\nu }}_{\tau }^{}$ neutrinos at the source, and an accurate value of $\xi$ can be used to test both the conventional mechanism and the postulated scenarios for cosmic neutrino production.

Comments: RevTex 14 pages, 4 PS figures, version to appear in Phys. Rev. D