Neutrino probe of cosmic ray astrophysics and new physics at sub-fermi distances

We show that if the evolution of cosmic ray sources follows that of active galactic nuclei, the upper limit on the diffuse flux of tau neutrinos from the Pierre Auger Observatory marginally constrains the proton fraction at the end of the energy spectrum. We also discuss prospects to uncover new physics leptophobic interactions using future Auger data.Comment: Talk given at SUSY09, the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions, Boston 2009. To be published in the Conference Proceeding