Studies of Ionization Backgrounds in Noble Liquid Detectors For Dark Matter Searches -- Eli Mizrachi (UMD)

Thursday 11 Apr 2024, 12:30 → 13:30 America/Los_Angeles

48/2-224 - Madrone (SLAC)

Recent interest in new sub-GeV dark matter models has resulted in a demand for detection thresholds at or near the single electron limit in liquid xenon or argon time projection chambers (TPCs). However, potential signals are currently obscured by delayed ionization backgrounds (“electron-trains”) which persist for seconds after an ionization event occurs. Electron-trains have been observed in many different TPC-based experiments, but their cause is only partially understood. This talk will provide an overview of electron-trains in various contexts, as well as possible strategies to mitigate them. 

First, a detailed characterization of electron-trains in the LZ experiment is presented, including new evidence of a dependence on detector conditions. The characterization also informed the development of an electron-train veto for LZ’s first WIMP search, which set world-leading limits on the spin-independent and spin-dependent WIMP-nucleon cross-sections for medium and high-mass WIMPs. 

 Next, details are given on hardware upgrades performed in XeNeu, a small xenon TPC at Lawrence Livermore National Lab. These include replacing plastics with low-outgassing metal and machinable ceramic components, as well as a replacement of XeNeu’s photomultiplier tube array with silicon photomultipliers. The resulting reduction in the intensity of electron-trains and better position resolution from the respective upgrades will improve future studies of low energy interactions and phenomena. A high energy nuclear recoil calibration, and a search for the Migdal effect with XeNeu are also summarized.

 

Finally, the development of CoHerent Ionization Limits in Liquid Argon and Xenon (CHILLAX), a new xenon-doped dual-phase argon test stand is reported. CHILLAX recently demonstrated stable operation with percent-level xenon concentrations in liquid argon. The possible benefits to ionization signal production and collection from xenon-doped argon are expected to result in lower detection thresholds.
 

Join from PC, Mac, Linux, iOS or Android: https://stanford.zoom.us/j/98973156241?pwd=cEU5RFdlVXoyc0JTeTlDMkozKzQ5UT09

2024-04-12-slac-fpd-0.2.2.pdf

video1506197637.mp4