| Summary: | The Antarctic Muon and Neutrino Detector Array (AMANDA) is designed to detect high energy neutrinos using the three kilometer thick ice cap covering the South Pole as a target and Cherenkov medium. Neutrinos that undergo charged current interactions with nucleons in the ice will produce ultrarelativistic charged leptons, which are detected through their Cherenkov and stochastic radiation by a three dimensional array of phototubes embedded in the ice cap at depths of 1500 to 2000 meters. The background to the observation of neutrinos is the flux of penetrating muons produced in cosmic ray showers in the atmosphere. This flux is approximately one million times the neutrino flux. To reject this background, we look downward, using the Earth to filter out all particles except neutrinos. To demonstrate the correct operation of the detector, we observe atmospheric neutrinos, which are produced in cosmic ray showers in the Northern Hemisphere. The flux, energy spectrum, and angular distribution of these neutrinos are relatively well known, making them a convenient calibration source. This work describes algorithms that have been developed to reconstruct and identify upgoing neutrinos in data recorded during the austral winter of 1997. A total of 204 neutrino candidates are identified, containing less than 10% background from misreconstructed downgoing muons. The neutrinos observed are found to agree with theoretical predictions of the atmospheric flux within the estimated systematic uncertainties. Limits are placed on high energy neutrino emission from known astronomical sources of very high energy gamma rays.
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