Studies of the muon-induced neutron background in LSM: detector concept and status of the installation

TL;DR

This paper discusses the background caused by muon-induced neutrons in dark matter detection experiments, presenting simulation and measurement efforts to understand and mitigate this background in the LSM underground laboratory.

Contribution

It reports on the development and deployment of a neutron counter integrated with the muon veto system at LSM, and presents detailed GEANT4 simulations and measurements of muon-induced neutrons.

Findings

Neutron background from muons is significant for dark matter detection.

The neutron counter effectively monitors neutrons in coincidence with muons.

Simulations and measurements help improve background understanding.

Abstract

A good particle candidate for Cold Dark Matter (CDM) is the supersymmetric neutralino or more generally a weakly interacting massive particle (WIMP). The expected interaction rate of WIMPs with the detector medium in the direct detection experiments is below 0.01 events/kg/day. This makes a good knowledge of the background conditions highly important, especially with ever increasing sensitivity of the detectors. One of the background components is related to cosmic muons and in particular to muon-induced neutrons. Detailed studies carried out by the Edelweiss collaboration in this respect are presented. This activity includes GEANT4 simulations with full event topology as well as a dedicated measurement with a new neutron counter installed in the fall of 2008 in LSM (Laboratoire Souterrain de Modane, France). This counter is incorporated into the existing muon veto system thus allowing to monitor neutrons in coincidence with the incoming muons.