University of Pennsylvania
Department of Physics and Astronomy
High Energy Physics Seminar

Abstract

Data from the MACRO detector was utilized to perform a measurement of the neutrino-induced muon flux in the energy range of several hundred 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, the data is most compatible with a neutrino mass-squared difference in the range 0.001 < Dm^2 < 0.01 eV^2.