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

Design and initial performance of the Askaryan Radio Array prototype EeV neutrino detector at the South Pole

We report on studies of the viability and sensitivity of the Askaryan Radio Array (ARA), a new initiative to develop a Teraton-scale ultra-high energy neutrino detector in deep, radio-transparent ice near Amundsen-Scott station at the South Pole. An initial prototype ARA detector system was installed in January 2011, and has been operating continuously since then. We describe measurements of the background radio noise levels, the radio clarity of the ice, and the estimated sensitivity of the planned ARA array given these results, based on the first five months of operation. Anthropogenic radio interference in the vicinity of the South Pole currently leads to a few-percent loss of data, but no overall effect on the background noise levels, which are dominated by the thermal noise floor of the cold polar ice, and galactic noise at lower frequencies. We have also successfully detected signals originating from a 2.5 km deep impulse generator at a distance of over 3 km from our prototype detector, confirming prior estimates of kilometer-scale attenuation lengths for cold polar ice. These are also the first such measurements for propagation over such large slant distances in ice. Based on these data, ARA-37, the ˜200 km2 array now in its initial construction phase, will achieve the highest sensitivity of any planned or existing neutrino detector in the 1016-1019 eV energy range.SCOPUS: ar.jinfo:eu-repo/semantics/publishe