New results on atmospheric neutrinos from Soudan 2

Neutrino interactions recorded in a 5.1 fiducial kiloton-year exposure of the Soudan-2 iron tracking calorimeter are analyzed for effects of neutrino oscillations. Using contained single track and single shower events, we update our measurement of the atmospheric nu (mu)/nu (e) ratio-of-ratios and find R = 0.68 +/- 0.11 +/- 0.06. Assuming this anomalously low R-value is the result of nu (mu) flavor disappearance via nu (mu) to nu (tau) oscillation, we select samples of charged current events which offer good resolution, event-by-event, for LIE, reconstruction. Oscillation-weighted Monte Carlo events are fitted to these data events using a chi (2) function summed over bins of log(L/E-nu). The region allowed in the (sin(2) 2 theta, Deltam(2)) plane at 90% CL is obtained using the Feldman-Cousins procedure: 0.46 < sin(2) 2<theta> less than or equal to 1.0 and 2.2 x 10(-4) < <Delta>m(2) ( 2.2 x 10(-2)eV(2). A small but relatively energetic sample of partially contained nu (mu) events has also been isolated. Their distribution in log(L/E-vis) relative to null oscillation Monte Carlo is compatible with nu (mu) to nu (tau) oscillation scenarios within the parameters region allowed by our contained events.