Performance Measurements of a High-Efficiency Cosmic Ray Veto Detector for the Mu2e Experiment

The Mu2e experiment at Fermilab will search for the charged lepton flavor violating process of coherent muon-to-electron conversion in the presence of a nucleus with a sensitivity four orders of magnitude beyond current limits. The experiment will have a single event sensitivity of about 3×10−17 while limiting the total background to about 0.5 events. One potential background is due to cosmic-ray muons producing an electron that is indistinguishable from signal within the Mu2e apparatus. The cosmic-ray-veto (CRV) system of the Mu2e experiment is tasked with vetoing cosmic-ray-induced backgrounds with high efficiency, without inducing significant dead time and while operating in a high-intensity environment. Efforts to measure the relative and absolute performance of CRV detector components will be discussed.