Energy and angular distribution of upward ultrahigh-energy neutrinos and signals of low scale gravity: Role of tau decay

Abstract

We present extensive results and analysis of energy and angular distributions of diffuse UHE $\nu_{e}$, $\nu_{\mu}$, and $\nu_{\tau}$ fluxes propagated through earth, with and without augmentation of the standard model interactions by low scale gravity. With propagated fluxes in hand we estimate event rates in a $1km^{3}$ detector in ice with characteristics of ICECUBE. We determine that, at 0.5PeV energy threshold, there is a significant difference in the ratios of down shower events to upward muon events between the standard model and the low scale gravity cases with 1TeV and 2TeV mass scales. The same is true for energy threshold at 5PeV. Though the difference is large in all flux models, statistical significance of this difference depends on the flux models, especially at 5PeV and above. Both flavor assumptions, $\nu_{e}$, $\nu_{\mu}$, $\nu_{\tau}::1$, 2, 0 and $% \nu_{e}$, $\nu_{\mu}$, $\nu_{\tau}::1$, 1, 1, and all flux models show large differences. Though rates of tagged events are low, we find that $\nu_{\tau}$ regeneration by $\tau $ decay may play an important role in disclosing deviations from standard model predictions at energies in the neighborhood of 1 PeV for 1TeV-scale gravity, for example. We emphasize those analyses whose sensitivity to new physics is independent of the flux model assumed.