Cosmic UHE Neutrino Signatures

Abstract

Utilizing the unique and reliable ultrasmall--$x$ predictions of the dynamical (radiative) parton model, nominal event rates and their detailed energy dependence caused by a variety of cosmic UHE neutrino fluxes are calculated and analyzed. In addition, maximal Regge--model inspired small--$x$ structure functions are employed for obtaining optimal rates which do not necessarily require `new' physics interpretations. Upward $\mu^+ +\mu^-$ event rates are estimated by taking into account total and nadir--angle dependent regeneration effects due to neutral current interactions. For exploring extragalactic neutrino sources at highest energies (\raisebox{-0.1cm}{$\stackrel{>}{\sim}$} $10^8$ GeV) with modern (future) ground--level telescopes, we analyze horizontal air shower event rates and shower events caused by Earth--skimming tau--neutrinos, in particular their detailed shower-- and cosmic neutrino--energy dependence. As an illustration of `new physics' implications we estimate the relevant horizontal air shower event rates due to spin--2 Kaluza--Klein `graviton' exchanges in neutral current neutrino--quark and neutrino--gluon interactions at low TeV--scales.