Scintillation efficiency and ionization yield of liquid xenon for mono-energetic nuclear recoils down to 4 keV

Abstract

Liquid Xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this paper, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency due to the electric field in LXe, finding no significant field dependence.

Figures (16)

• Figure 1: (Color online) Illustration of the signal production and collection in a two-phase xenon detector.
• Figure 2: (Color online) The setup for nuclear recoil scintillation efficiency measurement in LXe. Not drawn to scale.
• Figure 3: (Color online) Schematic of the dual phase LXe detector. Spaces not drawn were filled with PTFE pieces. PMTs, LXe and xenon gas regions drawn to scale.
• Figure 4: (Color online) Trigger system used in the dual phase runs. The PMT signals are summed and integrated to select the $S2$ signals. The organic scintillator signal generates a 15 $\mu$s pulse. This pulse and the $S2$ signals in coincidence trigger the acquisition system. For the single phase runs, triple coincidence of the $S1$ signals and the organic scintillator signal triggers the acquisition system.
• Figure 5: (Color online) Scintillation light yield for 122 keV gamma rays in the LXe detector running in single phase. The left histogram was taken at 1.5 kV/cm yielding $4.8 \pm 0.1$ pe/keVee and a resolution ($\sigma/E$) of 18%. The right histogram was taken at 0.0 kV/cm yielding $10.8 \pm 0.1$ pe/keVee and a resolution of 8.8%.