30TH INTERNATIONAL COSMIC RAY CONFERENCE An upper limit on the electron-neutrino flux from the HiRes instrument

Air-fluorescence detectors such as the High Resolution Fly’s Eye (HiRes) instrument are very sensitive to upward-going, Earth-skimming ultrahigh energy electron-neutrino-induced showers. This is due to the relatively large interaction cross sections of these high-energy neutrinos and to the LandauPomeranchuk-Migdal (LPM) effect. The LPM effect is responsible for a significant decrease in the cross sections for bremsstrahlung and pair production, rendering charged-current electron-neutrino-induced showers occurring deep in the Earth’s crust detectable as they exit the Earth into the atmosphere. A search for upward-going neutrino-induced showers in the entire HiRes-II monocular dataset has yielded a null result. From an LPM calculation of the energy spectrum of charged particles as a function of primary energy and depth for electron-induced showers in rock, we calculate the shape of the resulting profile of these showers in air. A full detector Monte Carlo simulation to determine the detector response to upwardgoing electron-neutrino-induced cascades is described and an upper limit on the flux of electron-neutrinos is given.