ULTRAHIGH-ENERGY NEUTRINO-NUCLEON CROSS-SECTION AND RADIATIVE-CORRECTIONS

Several proposals exist to detect cosmic neutrinos of energy from tens of GeV up to the highest energies observed for cosmic rays, similar t o 10(20) eV, or possibly even beyond. Detection efficiencies depend cr ucially on the neutrino-nucleon cross section at these energies at whi ch radiative corrections beyond the lowest order approximation could b ecome non-negligible. The differential cross sections can be modified by more than 50% in some regions of phase space. Estimates of correcti ons to the quantities most relevant for neutrino detection at these en ergies give, however, less dramatic effects: The average inelasticity in the outgoing lepton is increased from similar or equal to 0.19 to s imilar or equal to 0.24. The inclusive cross section is reduced by rou ghly half a percent. The dominant uncertainty of the standard model ul trahigh energy neutrino-nucleon cross section therefore still comes fr om uncertainties of the parton distributions in the nucleon at very lo w momentum fractions.