Neutrino Oscillation Effects in Soudan-2 Upward-stopping muons

TL;DR

This paper reports on the analysis of upward-stopping and downward-going muons in the Soudan-2 detector, providing evidence for neutrino oscillations by comparing observed muon fluxes with atmospheric neutrino flux predictions.

Contribution

It presents a detailed analysis of upward-stopping muons and their impact on constraining neutrino oscillation parameters using Soudan-2 data.

Findings

Upward-going muon sample shows a significant depletion compared to predictions.

Inclusion of both samples tightens constraints on oscillation parameters.

Results support the neutrino oscillation hypothesis over no-oscillation.

Abstract

Upward-going stopping muons initiated by atmospheric \numu and \anumu interactions in the rock below the Soudan 2 detector have been isolated, together with a companion sample of neutrino-induced single muons, created within the detector, which travel downwards and exit. The downward-going sample is consistent with the atmospheric-neutrino flux prediction, but the upward-going sample exhibits a sizeable depletion. Both are consistent with previously reported Soudan-2 neutrino-oscillation results. Inclusion of the two samples in an all-event likelihood analysis, using recent 3D-atmospheric-neutrino-flux calculations, reduces both the allowed oscillation parameter region and the probability of the no-oscillation hypothesis.