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Abstract:

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of νμ and ν̄μ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving Rup/downdata/Rup/downMC=0.62-0.14+0.19(stat.) ±0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field νμ and ν̄μ interactions are separated. The ratio of ν̄μ to νμ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving Rν̄μ/νμdata/Rν̄μ/νμMC=0.96-0. 27+0.38(stat.)±0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for νμ and ν̄μ. © 2006 The American Physical Society.

Abstract:

Data on low-energy hadron production in collisions of nucleons, pions and kaons with light nuclei are needed for many astrophysical and accelerator applications. Modern simulations have reached a level of accuracy that the lack of detailed understanding of hadron production processes has become one of the most important limitations to further improvements. After giving some examples of hadro-production processes in astrophysics and neutrino experiments we briefly review existing fixed-target data on light nuclei. Preliminary results and prospects of current CERN measurements (HARP, NA49) are discussed.