Measurements of scintillation efficiency and pulse shape for low energy recoils in liquid xenon

Abstract

Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is 0.22 ± 0.01 in the recoil energy range 40 keV -70 keV. Under the assumption of a single dominant decay component to the scintillation pulse-shape the log-normal mean parameter T 0 of the maximum likelihood estimator of the decay time constant for 6 keV < E ee < 30 keV nuclear recoil events is equal to 21.0 ns ± 0.5 ns. It is observed that for electron recoils T 0 rises slowly with energy, having a value ∼ 30 ns at E ee ∼ 15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse-shape. PACS: 95.35.+d, 29.40.Mc, 61.25.Bi

Scintillation efficiency of liquid xenon for nuclear recoils with the energy down to 5keV

“…In the range from 40 keV to 140 keV, it is in a good agreement with previously published results [3,4] but far from the value referred in [2]. The general trend is similar to that observed for iodine recoils in NaI(Tl), where an increase of the efficiency is also seen at recoil energies below ≈20 keV [9,10], and seems to disagree with theoretical estimates [11,12].…”

“…However, the values measured by these experiments are inconsistent; efficiencies about 0.5 [2] and 0.2 [3,4] were reported. Furthermore, the existing data does not cover the energies below 40 keV, of utmost importance for WIMP search experiments.…”

“…The scintillation efficiency of liquid xenon for nuclear recoils normalized to that for gamma-rays has been measured previously for recoil energies ranging from 40 keV to 150 keV [2][3][4]. However, the values measured by these experiments are inconsistent; efficiencies about 0.5 [2] and 0.2 [3,4] were reported.…”

The ZEPLIN III Detector; Results from Surface Calibrations

“…S2/S1 ratio as a function of S1 for singlescatter events with an Am-Be source. For elastic nuclear recoil events (population A) the energy scale must be multiplied by 1.95, coming from a combination of the inverse quenching factor, (1/0.19 [14][15][16]) and the relative S1 suppression factor at our operating field (∼0.37). Population C are γ-rays.…”

The ZEPLIN-III dark matter detector: Performance study using an end-to-end simulation tool

“…A zerofield quenching factor QF = 0.22 [26] was used in the simulation regardless of energy. Very recent data agree with this value at a few tens of keV (nuclear-recoil energy, 'keVnr'), but the trend at lower energies is still somewhat uncertain [28,29].…”