## Abstract

A total of 137 upward stopping muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 516 detector live days. The measured muon flux is 0.39 ± 0.04(stat.) ± 0.02(syst.) × 10^{-13} cm^{-2}s^{-1}sr^{-1} compared to an expected flux of 0.73 ± 0.16(theo.) × 10^{-13} cm^{-2}s^{-1}sr^{-1}. Using our previously-published measurement of the upward through-going muon flux, we calculate the stopping/through-going flux ratio ℛ, which has less theoretical uncertainty. The measured value of ℛ = 0.22 ± 0.02(stat.) ± 0.01(syst.) is significantly smaller than the value 0.37_{-0.04}^{+0.05}(theo.) expected using the best theoretical information (the probability that the measured ℛ is a statistical fluctuation below the expected value is 0.39%). A simultaneous fitting to zenith angle distributions of upward stopping and through-going muons gives a result which is consistent with the hypothesis of neutrino oscillations with the parameters sin^{2}2θ > 0.7 and 1.5 × 10^{-3} < Δm^{2} < 1.5 × 10^{-2} eV^{2} at 90% confidence level, providing a confirmation of the observation of neutrino oscillations by Super-Kamiokande using the contained atmospheric neutrino events.

Original language | English |
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Pages (from-to) | 185-193 |

Number of pages | 9 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 467 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - 1999 |

## Keywords

- Atmospheric muon neutrinos
- Cosmic rays
- Neutrino oscillations
- Super-Kamiokande
- Upward stopping muons
- Upward throughgoing muons

## ASJC Scopus subject areas

- Nuclear and High Energy Physics