Cosmic ray muon induced neutrons
The main reason for operating dark matter detectors deep underground is to escape cosmic ray muons. These are penetrating particles generated by high energy particles from space impacting the upper atmosphere. Vetoing the muons themselves is 'easy', but the muons can produce high energy neutrons near the detectors that can potentially mimic the signals we expect from dark matter. We used the ZEPIN-III veto to measure the rate at which neutrons are produced by cosmic ray muons in lead, useful for future projects.