Ultra High Energy Neutrino-Nucleon Scattering*

We study the scattering of ultra high energy neutrinos ($10^{16}-10^{22} eV$) on nucleons. The cross section is dominated by small $x$ gluons in the nucleon. We use the color glass condensate formulation of small $x$ QCD to calculate the neutrino-nucleon cross section and compare the results with those from the various DGLAP based parameterizations of the gluon distribution function. We finally examine the contribution of very small $x (\leq 10^{-7})$ gluons to the cross section.