Counting muons to probe the neutrino mass spectrum

TL;DR

This paper proposes a long baseline experiment using muon neutrino beams and large detectors to determine the neutrino mass spectrum by counting muon events, leveraging recent insights into neutrino mixing angles.

Contribution

It introduces a feasible experimental setup with specific parameters to identify the neutrino mass hierarchy through muon counting, utilizing existing technology and large-scale detectors.

Findings

Expected about 1000 muon events in the experiment.

A 30% difference in spectra can distinguish the mass hierarchy.

Optimal detection occurs between 4 and 10 GeV energy range.

Abstract

The experimental evidence that \theta_{13} is large opens new opportunities to identify the neutrino mass spectrum. We outline a possibility to investigate this issue by means of conventional technology. The ideal setup turns out to be long baseline experiment: the muon neutrino beam, with 10^{20} protons on target, has an average energy of 6 (8) GeV; the neutrinos, after propagating 6000 (8000) km, are observed by a muon detector of 1 Mton and with a muon energy threshold of 2 GeV. The expected number of muon events is about 1000, and the difference between the two neutrino spectra is sizeable, about 30%. This allows the identification of the mass spectrum just counting muon tracks. The signal events are well characterized experimentally by their time and direction of arrival, and 2/3 of them are in a region with little atmospheric neutrino background, namely, between 4 GeV and 10 GeV. The distances from CERN to Baikal Lake and from Fermilab to KM3NET, or ANTARES, fit in the ideal range.