Measurement of the atmospheric neutrino-induced upgoing muon flux using MACRO

Abstract

We present a measurement of the flux of neutrino-induced upgoing muons (<Eν >∼ 100 GeV) using the MACRO detector. The ratio of the number of observed to expected events integrated over all zenith angles is 0.74 ±0.036(stat) ±0.046(systematic) ±0.13(theoretical). The observed zenith distribution for −1.0 ≤ cos θ ≤ −0.1 does not fit well with the no oscillation expectation, giving a maximum probability for χ 2 of 0.1%. The acceptance of the detector has been extensively studied using downgoing muons, independent analyses and Monte-Carlo simulations. The other systematic uncertainties cannot be the source of the discrepancies between the data and expectations.We have investigated whether the observed number of events and the shape of the zenith dis-1

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