Atmospheric neutrino induced muons in the MACRO detector

TL;DR

This paper reports on the measurement of neutrino-induced muons in the MACRO detector, revealing a deficit in upward-going muons consistent with neutrino oscillations and suggesting maximum mixing with specific mass-squared differences.

Contribution

First measurement of neutrino-induced muon flux in MACRO showing evidence for neutrino oscillations with maximum mixing and specific mass-squared differences.

Findings

Observed upward-throughgoing muons are 26% fewer than expected.

Zenith angle distribution does not match expectations without oscillations.

Data consistent with neutrino oscillations with maximum mixing and Dm2 of a few times 10^-3 eV^2.

Abstract

A measurement of the flux of neutrino-induced muons using the MACRO detector is presented. Different event topologies, corresponding to different neutrino parent energies can be detected. The upward throughgoing muon sample is the larger event sample. The observed upward-throughgoing muons are 26% fewer than expected and the zenith angle distribution does not fit with the expected one. Assuming neutrino oscillations, both measurements suggest maximum mixing and Dm2 of a few times 10-3 eV2. The other samples are due to the internally produced events and to upward-going stopping muons. These data show a regular deficit of observed events in each angular bin, as expected assuming neutrino oscillations with maximum mixing, in agreement with the analysis of the upward-throughgoing muon sample.