Ultrahigh-Energy Neutrino Interactions

TL;DR

This work reframes ultrahigh-energy neutrino interactions through updated nucleon structure information, showing that modern parton distributions significantly raise νN cross sections at the highest energies and introduce substantial small-x uncertainties. It systematically evaluates νN and νe–electron interactions, Earth attenuation, atmospheric effects, and shadowing by celestial bodies, then translates these into predicted event rates for large-scale detectors under several astrophysical flux models. Key findings include a ~2.4× increase in the nominal νN cross section at 10^20 eV relative to older estimates and an overall uncertainty of a factor of ~2 due to small-x extrapolations, with downward-going events offering the best prospects for detecting extragalactic neutrinos in the near term. The results inform design and expected yields for km^3-scale neutrino telescopes and highlight the potential to probe AGN and cosmogenic neutrino fluxes, as well as W− resonance phenomena in ¯νe e scattering.

Abstract

Cross sections for the interactions of ultrahigh-energy neutrinos with nucleons are evaluated in light of new information about nucleon structure functions. For $10^{20}$--eV neutrinos, the cross section is about 2.4 times previous estimates. We also review the cross sections for neutrino interactions with atomic electrons. Some consequences for interaction rates in the Earth and for event rates from generic astrophysical sources in large-scale detectors are noted.

Figures (22)

• Figure 1: Comparison of the light-quark sea at $Q^{2}=M_{W}^{2}$ for various parton distributions. Of the MRS distributions, D_ (A') is the most (least) singular.
• Figure 2: Components of the $\nu N$ charged-current cross section as functions of the neutrino energy for the CTEQ3 distributions.
• Figure 3: Integral cross section $(1/\sigma)\int_{0}^{x^{\mathrm{max}}}dx\:d\sigma/dx$ for the charged-current reaction $\nu_{\mu}N \rightarrow \mu^{-}+\hbox{anything}$ at $E_{\nu}= 10^{5}, 10^{7},\hbox{and}10^{9}\hbox{GeV}$. As the neutrino energy increases, the dominant contributions come from smaller values of $x$.
• Figure 4: Energy dependence of the $\nu N$ and $\bar{\nu}N$ charged-current cross sections according to the CTEQ3 parton distributions. The EHLQ-DLA prediction QRW for the $\nu N$ cross section is also shown, together with the $\nu N$ cross section based on the unevolved EHLQ structure functions with $Q^{2}$ fixed at $Q_{0}^{2}=5\hbox{GeV}^{2}$.
• Figure 5: The charged-current cross section for $\nu_{\mu}$ interactions with an isoscalar nucleon. The parametrization of Frichter, FMcKR is shown for $5 \times 10^{4}\hbox{GeV} < E_{\nu} < 5\times 10^{7}\hbox{GeV}$. The data point is an average of measurements by the ZEUS and H1 Collaborations at HERA h1b.