Professor Dr.rer.nat. Dipl.Phys. Alfons Weber FInstP, MA Ox

Abstract:

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 ν μ and ν ̄μ interactions, and 701 contained-vertex showers, composed mainly of charged-current ν e and ν ̄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 ν μ and ν ̄μ events. The observed ratio of ν ̄μ to ν μ events is compared with the MonteCarlo (MC) simulation, giving a double ratio of Rν̄/νdata/ Rν̄/νMC=1.03±0.08(stat)±0.08(syst). The ν μ and ν ̄μ 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 |Δm2|=(1.9±0.4)×10 -3eV2 and sin22θ>0.86. The fit is extended to incorporate separate ν μ and ν ̄μ oscillation parameters, returning 90% confidence limits of |Δm2|-|Δm ̄2|=0.6- 0.8+2.4×10 -3eV2 on the difference between the squared-mass splittings for neutrinos and antineutrinos. © 2012 American Physical Society.

Abstract:

The pi-zero detector (POD) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the POD is to measure the relevant cross-sections for neutrino interactions that generate π0s, especially the cross-section for neutral current π0 interactions, which are one of the dominant sources of background to the νμ→ νe appearance signal in T2K. The POD is composed of layers of plastic scintillator alternating with water bags and brass sheets or lead sheets and is one of the first detectors to use Multi-Pixel Photon Counters (MPPCs) on a large scale. © 2012 Elsevier B.V. All rights reserved.

Abstract:

In this paper we describe how two or more experimental results can be combined within the procedure of Feldman and Cousins, to provide combined confidence limits on the physical parameters of interest. We demonstrate the technique by combining the recent electron neutrino appearance results from T2K and MINOS. Our best fit point is sin 2 2θ 13 = 0.08 (0.11) and δ = 1.1 (2.0)π; in addition we exclude sin2 2θ 13 = 0 at 2.7σ (2.8σ) for the normal (inverted) neutrino mass hierarchy. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.