Cosmic Backgrounds at the Daya Bay Reactor Antineutrino Experiment
Mitchell, Ian Alexander 1989-
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The measurement of physical quantities connected to rare events, such as neutrino interactions, is complicated by the presence of processes that can mimic them, called backgrounds. One type of background for underground experiments is the production of neutrons in material around the detector, called rock neutrons. Seven months of data from one experimental hall of the Daya Bay Reactor Antineutrino Experiment were analyzed to identify rock neutron events with the goal of computing the rate of rock neutron events at the experiment. Rock neutron candidates were identified through the coincidence of a fast neutron moderation signal and neutron capture within the detector following a muon signal that did not trigger the water and scintillator portions of the detector. Over this period, this analysis identified n = 38 candidate events and a background of b = 56 events. The application of the Rolke-Lopez statistical method to this data produced an upper rate limit estimate of 0.0005 events/detector/day at the 90\% confidence level in this experimental hall, showing that this background has a negligible impact on the neutrino signal from the same detectors of over 650 events/detector/day.