A study of atmospheric neutrino oscillations in the Fréjus experiment

Abstract Atmospheric neutrino interactions have been studied with the Frejus proton decay detector using a total fiducial sensitivity of 1.56 kT yr. The atmospheric neutrino interaction sample has been compared to a Monte Carlo simulation which includes neutrino oscillations. The v e ( v e ) ∌v μ , ( v μ ), v e ( v e ) ∌v τ v μ ( v μ ) ∌v τ ( v τ) oscillations channels have been studied using the ratio of electron to muon charged current events. Three independent analyses have been performed and no evidence for neutrino oscillations has been found. The resulting limits on Δm 2 for maximal mixing are more restrictive by more than one order of magnitude with respect to earlier measurements.