Distributions of time intervals from each triggered event in four different SuperCDMS HVeV Detectors (NF-C, R1, NF-H, and NF-C). Strong time correlations are observed as sharp peaks around zero seconds. The red-shaded window shows the ±20 ms window excluded by an anticoincidence live-time selection. Figure replicated from Albakry et al. (2024).
A new paper by the SuperCDMS collaboration places improved constraints on dark matter with a small array of cryogenic detectors (named HVeV). These detectors were operated in the NEXUS underground test stand, which is situated 100 meters underground in the Fermilab NuMI hall. The data revealed a background that was time-correlated between detectors (shown in the figure), thus bolstering an earlier hypothesis on luminescence in the surrounding PCB holders. The 225 meters-water-equivalent overburden at NuMI, along with careful control of radioactive contaminants, enables the study of backgrounds that are subdominant to natural environmental radioactivity. Such studies are critical to disentangling potential dark matter signals from more mundane phenomena such as this.
A preprint on this result can be found on the arXiv in Albakry et al. (2024).