Penetration of the Earth by ultrahigh energy neutrinos predicted by lowxQCD

We calculate the cross sections for neutrino interactions with (isoscalar) nuclear targets in the energy domain all the way up to ${10}^{12}\hspace{0.5em}\mathrm{GeV}$. Small x QCD effects are included by using a unified BFKL-DGLAP formalism which embodies non-leading $\log 1/x$ contributions. The few free parameters which specify the input parton distributions are determined by fitting to DESY HERA deep inelastic data. The attenuation of neutrinos transversing the Earth at different nadir angles is calculated for a variety of energy spectra for neutrinos originating from different sources (from active galactic nuclei, gamma ray bursts, top-down models), as well as for atmospheric neutrinos. For this purpose we solve the transport equation which includes regeneration due to neutral current neutrino interactions, in addition to attenuation.