Low energy atmospheric muon neutrinos in MACRO

TL;DR

This study analyzes low energy atmospheric muon neutrinos using the MACRO detector, observing a flux deficit consistent with neutrino oscillations, and compares results with higher energy neutrino data.

Contribution

First analysis of low energy atmospheric muon neutrinos in MACRO, providing evidence for neutrino oscillations at energies around 4 GeV.

Findings

Observed a flux deficit of muon neutrinos from below

Results support neutrino oscillation hypothesis

Data consistent with Monte Carlo predictions for above neutrinos

Abstract

The flux of low energy neutrinos (<E_nu>~ 4 GeV) has been studied with the MACRO detector at Gran Sasso via the detection of muon neutrinos interactions inside the apparatus, and of upward-going stopping muons. Data collected in ~3 y with the full apparatus were analyzed. The results are compatible with a deficit of the flux of atmospheric muon neutrinos from below, and no reduction from above, with respect to Monte Carlo predictions. The deficit and the angular distributions are interpreted in terms of neutrino oscillations, and compared with the MACRO results on the upward throughgoing muons (<E_nu>~ 100 GeV).