Speaker
Description
The NEWS-G collaboration uses spherical proportional counters to search directly for low-mass dark matter. Each counter is a metallic sphere filled with gas with high-voltage anodes at its centre producing a radial electric field. The interaction between a dark matter particle and a nucleus can ionize the gas, which leads to electron avalanches near the anodes and a detectable signal. The latest NEWS-G detector is a 140 cm diameter copper sphere currently taking data with various gases at SNOLAB.
Like many sensitive detectors of various types, we have found an unexplained excess of low-energy events, which is the main limit on NEWS-G's sensitivity. Our working hypothesis was that this relates to electron attachment to electronegative impurities, such as oxygen, in the detector gas. In fall 2024, we injected two small boluses of air into our detector volume (O$_2$ concentration of 11 ± 1 ppm each in 1400 L) and found proportionate changes in certain types of event. I will introduce the detector and discuss the issue of attachment, including the results of this injection experiment.
| Keyword-1 | dark matter |
|---|---|
| Keyword-2 | SNOLAB |
| Keyword-3 | gaseous detector |
