Measurement of theL/Edistributions of atmosphericνin Soudan 2 and their interpretation as neutrino oscillations

A deficit of atmospheric ${\nu }_{\mu }$ events, consistent with the hypothesis of neutrino oscillations, is observed in the 5.90 kiloton-year fiducial exposure of the Soudan 2 detector. An unbinned maximum likelihood analysis of the neutrino $L/E$ distribution has been carried out using the Feldman-Cousins prescription. The probability of the no oscillation hypothesis is $5.8\times {10}^{-4}.$ The 90% confidence allowed region in the ${\sin }^{2}2\theta ,\Delta m^2$ plane is presented. The region includes the 90% confidence allowed region of the Super-K experiment.