  Cubic kilometer neutrino telescopes are capable of probing fundamental
questions of ultra-high energy neutrino interactions. There is currently great
interest in neutrino interactions caused by low-scale, extra dimension models.
Above 1 PeV the cross section in low scale gravity models rises well above the
total Standard Model cross section. We assess the observability of this effect
in the 1 PeV - 100 PeV energy range of kilometer-scale detectors with several
new points of emphasis that hinge on enhanced neutral current cross sections. A
major point is the importance of ``feed-down'' regeneration of upward neutrino
flux, driven by new-physics neutral current interactions in the flux evolution
equations. Feed-down is far from negligible, and it is essential to include its
effect. We then find that the angular distribution of events has high
discriminating value in separating models. In particular the ``up-to-down''
ratio between upward and downward-moving neutrino fluxes is a practical
diagnostic tool which can discriminate between models in the near future. The
slope of the angular distribution, in the region of maximum detected flux, is
also substantially different in low-scale gravity and the Standard Model. These
observables are only weakly dependent on astrophysical flux uncertainties. We
conclude that angular distributions can reveal a breakdown of the Standard
Model and probe the new physics beyond, as soon as data become available.
