Intrinsic limits on resolutions in muon- and electron-neutrino charged-current events in the KM3NeT/ORCA detector

TL;DR

This study investigates the fundamental factors limiting energy and directional resolution in charged-current neutrino events at the KM3NeT/ORCA detector, focusing on hadronic cascade fluctuations and inelasticity effects.

Contribution

It identifies the primary physical processes that constrain resolution in neutrino detection, providing insights applicable to similar detectors and media.

Findings

Hadronic cascade fluctuations significantly affect resolution.

Inelasticity variation impacts energy and direction measurements.

Photon sampling limitations are less influential.

Abstract

Studying atmospheric neutrino oscillations in the few-GeV range with a multimegaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1 - 20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ice.