Measurement of neutron production in atmospheric neutrino interactions at Super-Kamiokande

TL;DR

This study measures neutron production in atmospheric neutrino interactions at Super-Kamiokande, comparing data with various models to improve understanding of nuclear effects in neutrino interactions.

Contribution

It provides the first detailed measurement of neutron yields over a wide energy range, validating and challenging current hadron-nucleus interaction models.

Findings

Neutron production varies significantly with interaction models.

Neutron detection efficiency is enhanced with gadolinium doping.

Model predictions show notable discrepancies with observed data.

Abstract

We present measurements of total neutron production from atmospheric neutrino interactions in water, analyzed as a function of electron-equivalent visible energy over a range of 30 MeV to 10 GeV. These results are based on 4,270 days of data collected by Super-Kamiokande, including 564 days with 0.011 wt\% gadolinium added to enhance neutron detection. Neutron signal selection is based on a neural network trained on simulation, with its performance validated using an Am/Be neutron point source. The measurements are compared to predictions from neutrino event generators combined with various hadron-nucleus interaction models, which include an intranuclear cascade model and a nuclear de-excitation model. We observe significant variations in the predictions depending on the choice of hadron-nucleus interaction model. We discuss key factors that contribute to describing our data, such as in-medium effects in the intranuclear cascade and the accuracy of statistical evaporation modeling.