Detection of atmospheric neutrinos with the first detection units of KM3NeT-ARCA

The KM3NeT Collaboration is constructing two deep-sea Cherenkov detectors in the Mediterranean Sea. The ARCA detector aims at TeV-PeV neutrino astronomy, while the ORCA detector is optimized for atmospheric neutrino oscillations at energies of a few GeV. The first detection units of the ARCA and ORCA detectors have been deployed off-shore the South of Italy and France, respectively. In this contribution, an analysis of the data collected with the first deployed detection units of the ARCA detector and the selection of a high-purity sample of atmospheric neutrinos is presented.