Abstract

This letter presents a combined measurement of the energy spectra of atmospheric νe and νμ in the energy range between ∼100 GeV and ∼50 TeV with the ANTARES neutrino telescope. The analysis uses 3012 days of detector livetime in the period 2007–2017, and selects 1016 neutrinos interacting in (or close to) the instrumented volume of the detector, yielding shower-like events (mainly from νe+ν‾e charged current plus all neutrino neutral current interactions) and starting track events (mainly from νμ+ν‾μ charged current interactions). The contamination by atmospheric muons in the final sample is suppressed at the level of a few per mill by different steps in the selection analysis, including a Boosted Decision Tree classifier. The distribution of reconstructed events is unfolded in terms of electron and muon neutrino fluxes. The derived energy spectra are compared with previous measurements that, above 100 GeV, are limited to experiments in polar ice and, for νμ, to Super-Kamiokande.

Highlights

  • This letter presents a combined measurement of the energy spectra of atmospheric νe and νμ in the energy range between ∼100 GeV and ∼50 TeV with the ANTARES neutrino telescope

  • Atmospheric neutrinos are secondary particles produced by cosmic ray (CR) primaries interacting in the Earth’s atmosphere

  • The simulation chain [26] starts with the generation of the event and comprises the generation of Cherenkov light, the inclusion of the environmental optical background extracted from real data, and the digitisation of the photomultiplier tube (PMT) signals following a run-byrun strategy

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Summary

Introduction

Atmospheric neutrinos are secondary particles produced by cosmic ray (CR) primaries interacting in the Earth’s atmosphere. Where γC R is the spectral index of the primary CRs. Above 100 GeV and up to some tens of TeV, atmospheric νe ’s come mostly from decays of neutral and charged kaons, and have the same spectral index of conventional νμ. Equal fluxes of νμ and νe are produced by the decays of charged and neutral D-mesons. Uncertainties on the conventional flux models at neutrino energies above 1 TeV are mainly due to a poor knowledge of primary CR energy spectrum and composition, and of hadronic interactions, in particular of strange quark production mechanisms [11]. The distributions of observed events are unfolded (§4) to obtain the energy spectra of both atmospheric νμ and νe , taking into account the detector acceptance (§5). The unfolded spectra are the sum of νe + νe and of νμ + νμ, averaged over the zenith region 90◦–180◦

The ANTARES detector and neutrino reconstruction algorithms
Event selection: signal and background
Unfolding procedure and detector acceptance
The unfolded energy spectrum
Results and conclusions

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