Speaker
Description
The DEAP-3600 detector is a large single-phase liquid-argon detector for WIMP dark matter. The experiment has run successfully at SNOLAB since 2016 and has world leading limits for WIMP-argon interactions. We use pulse-shape discrimination (PSD) to separate electromagnetic events (Ar-39 beta decay, gamma rays, ...) from the nuclear recoil events from WIMP-nuclear scattering. PSD is effective in liquid argon because the nuclear recoil events have a large density of energy deposition in the argon, resulting in preferential excitation to an Argon eximer singlet state that decays in nanoseconds, whereas electromagnetic events have a low density of energy deposition resulting in excited triplet states that decay in microseconds. We discuss the scintillation pulse shapes in DEAP-3600 and show our recent analysis of pulse-shape discrimination. At 18 keVee, we have achieved rejection of EM events with leakage of 1 part in 10^{10} with a nuclear recoil acceptance of 50%. We present these results and a detailed comparison showing the effectiveness of the prompt-fraction method and the likelihood ratio. We discuss detector effects such as long-lived TPB states and PMT afterpulsing.
| Reference to paper (DOI or arXiv) | https://arxiv.org/abs/2103.12202 |
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