Sterile neutrino oscillations in MINOS and hadron production in pC collisions

Abstract

MINOS is a long baseline neutrino oscillation experiment, starting with a muon-neutrino beam, for the precise measurement of the atmospheric neutrino oscillation parameters |Δm2| and θ23. The Near Detector measures the neutrino flux and spectra before oscillations. The beam propagates for 735 km to the Far Detector, which measures the depleted spectrum after oscillations. The depletion can be interpreted as vμ → vτ oscillations. Subdominant vμ → ve oscillations may be allowed if the mixing angle θ13 ≠ 0. The two detectors are functionally identical in order to cancel systematic errors when using the Near Detector data to constrain the Far Detector prediction. A crucial part of the analysis is the relative calibration between the two detectors, which is known at the 2% level. A calibration procedure to remove the time and temperature dependence of the detector response using through-going cosmic muons is presented here. Although the two-detector approach reduces the systematic uncertainties related to the neutrino flux, a cross check on the neutrino parent meson ratios is performed in this thesis. The cross sections of mesons produced in proton-carbon interactions from the NA49 experiment have been measured and the results have been compared to the MINOS expectations. A neutrino oscillation analysis allowing mixing to a sterile neutrino is performed, under the assumption that the additional mass splitting is Ο(1 eV2). The analysis uses the energy spectrum of the neutral current interaction products, as neutral current interactions are sensitive to sterile neutrino mixing but not to the active flavour neutrino mixing. The neutrino oscillation parameters have been found to be: |Δm2| = 2.43-0.18+0.21 x 10-3 eV2, θ23 = 40.27°-5.17+14.64, θ24 = 0.00°+5.99 and θ34 = 0.00°+24.57 under the assumption that θ13 = 12° (limited by the CHOOZ experiment) or |Δm2| = 2.43-0.18+0.20 x 10-3 eV2, θ23 = 39.09°-4.89+16.71, θ24 = 0.00°+4.79 and θ34 = 0.00°+17.39 if θ13 is assumed to be zero.