  Searches for physics beyond the Standard Model of particle physics are
performed at accelerators worldwide. Although having poorer detection
capabilities and large beam uncertainties, ultra high energy cosmic ray (UHECR)
experiments present a unique opportunity to look for new physics far beyond the
TeV. Nearly horizontal energetic neutrinos, seeing a large atmospheric target
volume and with negligible background from "ordinary" cosmic rays, are ideal to
explore rare processes.
  The sensitivity of present and planned experiments to different new physics
scenarios is estimated, including mini black-holes, excited leptons and
leptoquarks.
