Identifying Neutrino Mass Hierarchy at Extremely Small θ13 through Earth Matter Effects in a Supernova Signal

Collective neutrino flavor transformations deep inside a supernova are sensitive to the neutrino mass hierarchy even at extremely small values of theta(13). Exploiting this effect, we show that comparison of the antineutrino signals from a galactic supernova in two megaton class water Cherenkov detectors, one of which is shadowed by Earth, will enable us to distinguish between the hierarchies if sin(2)theta(13) less than or similar to 10(-5), where long baseline neutrino experiments would be ineffectual.