The Muon-Induced Neutron Indirect Detection EXperiment, MINIDEX

TL;DR

MINIDEX is a new experiment that measures muon-induced neutrons in high-Z materials, revealing discrepancies with simulations crucial for low-background physics experiments.

Contribution

The paper introduces MINIDEX and provides the first data on neutron production in lead, highlighting differences with existing Monte Carlo models.

Findings

Muon-induced neutron rates are 3-4 times higher in data than simulations.

Current Monte Carlo models do not accurately reproduce the time evolution of signals.

First experimental data on neutron transport in lead for low-background experiments.

Abstract

A new experiment to quantitatively measure neutrons induced by cosmic-ray muons in selected high-Z materials is introduced. The design of the Muon-Induced Neutron Indirect Detection EXperiment, MINIDEX, and the results from its first data taking period are presented as well as future plans. Neutron production in high-Z materials is of particular interest as such materials are used for shielding in low-background experiments. The design of next-generation large-scale experiments searching for neutrinoless double beta decay or direct interactions of dark matter requires reliable Monte Carlo simulations of background induced by muon interactions. The first five months of operation already provided a valuable data set on neutron production and neutron transport in lead. A first round of comparisons between MINIDEX data and Monte Carlo predictions obtained with two GEANT4- based packages is presented. The rate of muon-induced events is overall a factor three to four higher in data than predicted by the Monte Carlo packages. In addition, the time evolution of the muon-induced signal is not well described by the simulations.