CPC Seminar: High Voltage Electrode Backgrounds in the Context of S2-only Analyses in Dual-Phase Xenon TPCs

  • Oct. 3, 2022, 2:00 pm US/Central
  • DIR/ Curia II-WH2SW - Wilson Hall 2nd fl South West

Speaker: Ryan Linehan, Fermilab

Abstract: Approximately 15% of the matter density in the universe is composed of Standard Model particles, while the other 85% is composed of an enigmatic “dark” matter whose fundamental properties are unknown. In recent decades, there has been substantial interest in performing a direct detection of dark matter scatters on Standard Model particles, but currently no such signature has been verifiably observed. The LUX-ZEPLIN (LZ) experiment was built to perform such a direct detection of dark matter using a dual-phase xenon time projection chamber (TPC), which can observe both light and charge signals from an interaction in the xenon. This technology is critically dependent on maintaining strong drift and extraction fields in order to observe the charge signal. These fields are established by a set of four stainless steel wire mesh high voltage electrode grids that span the full width of the TPC. During operation, these grids achieve wire surface fields well above 15 kV/cm. These high fields can produce spurious charge signals and signals from real radioactive decays with atypical light-to-charge ratios, both of which can lead to low-energy backgrounds in LZ science data. These backgrounds can be problematic for low-threshold, “S2-only” analyses which rely only on observing the charge signal from an interaction. In this talk, we present an overview of the the LZ detector and its HV electrodes, and discuss efforts to understand electrode-induced backgrounds and their impacts on a future LZ S2-only analysis. Notably, we discuss a novel model for radiogenic grid backgrounds that lays the foundation for a rigorous S2-only WIMP search probing dark matter masses down to 1 GeV/c^2.

Zoom: https://fermipoint.fnal.gov/service/seminars
If you are interested in connecting to the talk remotely without a Fermilab Services account, you can contact Dylan Temples, dtemples@fnal.gov.