Ultrahigh energy neutrino scattering: an update

We update our estimates of charged and neutral current neutrino total cross sections on isoscalar nucleons at ultrahigh energies using a global (x, Q) fit, motivated by the Froissart bound [1], to the F2 (electron-proton) structure function utilizing the most recent analysis [2] of the complete ZEUS and H1 data sets from HERA I. Using the large Q, small Bjorken-x limits of the “wee” parton model, we connect the ultrahigh energy neutrino cross sections directly to the large Q, small x extrapolation of our new fit, which we assume saturates the Froissart bound [1]. We compare both to our previous work [3], which utilized only the smaller ZEUS [4] data set, as well as to recent results [5] of a calculation using the ZEUS-S based global perturbative QCD parton distributions using the combined HERA I results as input. Our new results substantiate our previous conclusions [3], again predicting significantly smaller cross sections than those predicted by extrapolating pQCD calculations to neutrino energies above 10 GeV.