Measurement of atmospheric neutrino flux consistent with tau neutrino appearance

Abstract

A search for the appearance of tau neutrinos from nu(mu)<->nu(tau) oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138 +/- 48(stat)+15/-32(syst) events is obtained with an expectation of 78 +/- 26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma.