Characterizing PTFE Fluorescence to Increase Sensitivity of WIMP Dark Matter Detectors*

Dual-phase xenon time projection chambers have world-leading sensitivity to direct detection of WIMP dark matter. Reducing backgrounds that could mimic a WIMP event is critical for improving discovery potential. At low-energy depositions, the few-photon and electron backgrounds hamper sensitivity to low-mass dark matter. A hypothesis for the dominant source of the few-photon background is long-lived fluorescence decays of detector materials, in particular from impurities present in PTFE (Teflon). To test this hypothesis, we constructed a testbed to measure delayed light emission of PTFE using an LED to stimulate fluorescence. Photon counts were recorded over time by a silicon photomultiplier within the chamber. We observed a distinct decay of photon counts at delayed times, suggestive of fluorescence. To confirm the source of delayed photons is from PTFE, an upgraded setup is underway to reduce systematics. In addition, we plan to test potential fluorescence of other detector materials used for future dark matter experiments.