Measurements of atmospheric neutrinos and antineutrinos in the MINOS far detector
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This paper reports measurements of atmospheric neutrino and antineutrino interactions in the MINOS Far Detector, based on 2553 live-days (37.9kton-years) of data. A total of 2072 candidate events are observed. These are separated into 905 contained-vertex muons and 466 neutrino-induced rock-muons, both produced by charged-current and interactions, and 701 contained-vertex showers, composed mainly of charged-current e and e interactions and neutral-current interactions. The curvature of muon tracks in the magnetic field of the MINOS Far Detector is used to select separate samples of and events. The observed ratio of to events is compared with the MonteCarlo (MC) simulation, giving a double ratio of R/data/ R/MC=1.030.08(stat)0.08(syst). The and data are separated into bins of L/E resolution, based on the reconstructed energy and direction of each event, and a maximum likelihood fit to the observed L/E distributions is used to determine the atmospheric neutrino oscillation parameters. This fit returns 90% confidence limits of |m2|=(1.90.4)10 -3eV2 and sin22>0.86. The fit is extended to incorporate separate and oscillation parameters, returning 90% confidence limits of |m2|-|m 2|=0.6- 0.8+2.410 -3eV2 on the difference between the squared-mass splittings for neutrinos and antineutrinos. 2012 American Physical Society.