A measurement of the neutrino -induced muon flux at the MACRO detector.

Data from the MACRO detector was utilized to perform a measurement of the neutrino-induced muon flux in the high energy range ⟨E nu⟩ ∼ 100 GeV. This measurement comprises a large sample (403.6 events after all fidelity cuts and background subtraction) from an exposure time of 4 years. This is contrasted with an expected event rate of 540 upward muons from a detailed Monte Carlo simulation of MACRO using as input the atmospheric neutrino flux of the Bartol group. This gives a ratio of 0.76 +/- 0.04(stat.) +/- 0.16(syst.) measured versus expected. Recent results from other experiments worldwide, most notably the Super-Kamioka collaboration in Japan, have exposed similar discrepancies in the measured versus expected fluxes of underground muons. A consistent explanation of these effects is that the neutrino flux undergoes flavor oscillations between source and detector. For simple two-flavor mixing, a mixing angle of sin2 2theta ≈ 1 and a mass-squared difference in the range 0.001 m2 eV2 best fits the observed muon neutrino flux.Ph.D.AstronomyHigh energy physicsPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132362/2/9963794.pd