Determination of responses of liquid xenon to low energy electron and nuclear recoils using a PandaX-II detector *

Abstract

We present a systematic determination of the responses of PandaX-II, a dual phase xenon time projection chamber detector, to low energy recoils. The electron recoil (ER) and nuclear recoil (NR) responses are calibrated, respectively, with injected tritiated methane or 220Rn source, and with 241Am-Be neutron source, in an energy range from 1-25 keV (ER) and 4-80 keV (NR), under the two drift fields, 400 and 317 V/cm. An empirical model is used to fit the light yield and charge yield for both types of recoils. The best fit models can describe the calibration data significantly. The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.

Dark Matter Search Results from the PandaX-4T Commissioning Run

“…It is verified that clean , 1 and 2 are all independent. A simultaneous fit of ER and NR response model is performed on the calibration data ( 220 Rn, 241 Am-Be, and D-D) in (S1, S2), with fast detector simulation including the following effects: photon detection, electron drifting, diffusion, extraction and amplification, non-uniformities of S1 and S2, and cut efficiencies [25,26]. The ER and NR response models follow the standard NEST 2.0 construction [27], with the light yield, charge yield, and recombination parameters fitted.…”

A Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics

“…Assuming a W-value of 11.5 eV [105], averaged over scintillation and ionization, leads to yields as high as ∼65 photons per keV for gamma rays that are of order ∼100 keV [106,107], similar to other excellent scintillators such as NaI and CsI. For nuclear recoils, the yields are still ∼10% of that, even below ∼10 keV [108,109]. Energy resolutions better than 1% (σ/E) have been achieved at MeV scales [102] and mm-level position resolution can routinely be achieved [91,110,111].…”

A Search for the Cosmic Ray Boosted Sub-GeV Dark Matter at the PandaX-II Experiment

“…The ER and NR signal response models in the PandaX-II detector are constructed under the NEST 2.0 prescription [64], with parameters fitted from calibration data [65]. Our background model includes tritium, 85 Kr, 127 Xe, 136 Xe, the so-called "flat ER" (including detector material radioactivity, radon, and neutrinos), neutrons and accidental events.…”

“…A profile likelihood ratio approach is used to set the CRDM signal exclusions [67], comparing fits to the data with pseudo-data sets produced at different values of m χ and σ χp . Since the distributions of background and CRDM signal in (t sid , E ee ) depend on their distributions in S1 and S2, our ER and NR model uncertainties [65] have to be properly incorporated. For illustration, the 90% contours of the ER and NR medians obtained through the calibration data [65] are overlaid in Fig.…”

“…Since the distributions of background and CRDM signal in (t sid , E ee ) depend on their distributions in S1 and S2, our ER and NR model uncertainties [65] have to be properly incorporated. For illustration, the 90% contours of the ER and NR medians obtained through the calibration data [65] are overlaid in Fig. 2a.…”