Probing neutrino flavor transition mechanism with ultrahigh energy astrophysical neutrinos

Abstract

Observation of ultrahigh energy astrophysical neutrinos and identification of their flavors have been proposed for future neutrino telescopes. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. The flavor transition mechanisms are well classified with our model-independent parametrization. We find that a new parameter $R\ensuremath{\equiv}{\ensuremath{\phi}}_{e}/({\ensuremath{\phi}}_{\ensuremath{\mu}}+{\ensuremath{\phi}}_{\ensuremath{\tau}})$ can probe directly the flavor transition in the framework of our model-independent parametrization, without the assumption of the ${\ensuremath{\nu}}_{\ensuremath{\mu}}\text{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ symmetry. A few flavor-transition models are employed to test our parametrization with this new observable. The observational constraints on flavor transition mechanisms by the new observable are discussed through our model-independent parametrization.