Comprehensive study of cosmogenic neutron production in large liquid scintillator detectors

TL;DR

This study benchmarks and refines simulations of cosmogenic neutron production in large liquid scintillator detectors, achieving improved agreement with experimental data and establishing a benchmark for future modeling efforts.

Contribution

It provides a comprehensive benchmarking of neutron yields against experimental data and introduces a refinement strategy for simulation models, especially GEANT4 hadronic physics lists.

Findings

BIC-based models match experimental neutron yields within 0.3%

Adjustments reduce simulation discrepancies from 20% to below 1%

Persistent underproduction of single-neutron and overproduction of multi-neutron events

Abstract

Neutrons produced by cosmic ray muons constitute a significant background for underground experiments investigating neutron oscillations, neutrinoless double beta decay, dark matter, and other rare event signals. This work benchmarks measured neutron yields and neutron multiplicities--with a focus on data from the Daya Bay Reactor Neutrino Experiment--against comprehensive simulations using three GEANT4 hadronic physics lists. These simulations are further refined via a TALYS-based adjustment of hadronic cross sections. For the BERT-based models, the adjustment reduces the discrepancy in the total neutron yield from about 20% to approximately 6%, while for the BIC-based models it improves the agreement from roughly 13% to the sub-percent level (~0.3%), indicating a markedly better consistency of the BIC-based models with the experimental data. Nevertheless, a clear tension persists: simulations systematically underproduce single-neutron events while overproducing multi-neutron events. The study establishes a reproducible benchmark for cosmogenic neutron modeling and proposes a targeted refinement strategy--including channel-specific reweighting and intranuclear cascade parameter tuning--to guide future model development.