A Review of Basic Energy Reconstruction Techniques in Liquid Xenon and Argon Detectors for Dark Matter and Neutrino Physics Using NEST

Abstract

Detectors based upon the noble elements, especially liquid xenon as well as liquid argon, as both single- and dual-phase types, require reconstruction of the energies of interacting particles, both in the field of direct detection of dark matter (weakly interacting massive particles WIMPs, axions, etc.) and in neutrino physics. Experimentalists, as well as theorists who reanalyze/reinterpret experimental data, have used a few different techniques over the past few decades. In this paper, we review techniques based on solely the primary scintillation channel, the ionization or secondary channel available at non-zero drift electric fields, and combined techniques that include a simple linear combination and weighted averages, with a brief discussion of the application of profile likelihood, maximum likelihood, and machine learning. Comparing results for electron recoils (beta and gamma interactions) and nuclear recoils (primarily from neutrons) from the Noble Element Simulation Technique (NEST) simulation to available data, we confirm that combining all available information generates higher-precision means, lower widths (energy resolution), and more symmetric shapes (approximately Gaussian) especially at keV-scale energies, with the symmetry even greater when thresholding is addressed. Near thresholds, bias from upward fluctuations matters. For MeV-GeV scales, if only one channel is utilized, an ionization-only-based energy scale outperforms scintillation; channel combination remains beneficial. We discuss here what major collaborations use.

A measurement of the mean electronic excitation energy of liquid xenon

“…The two-dimensional 2.82 keV distribution in S1-S2-space, shown in Fig. 4, right, features a slight asymmetry (skewness) that was also observed elsewhere [54,55]. This is due to DAQ and processing efficiencies, the low light level or charge loss and can be modelled with skew-Gaussians [56].…”

“…In Ref. [55] the larger S1 bias is explained by the fact that only upward S1 fluctuations above the S1 threshold are measured at such low light levels.…”

Neutrino Backgrounds in Future Liquid Noble Element Dark Matter Direct Detection Experiments

“…[124,125,126,127], andinvestigated in direct calibration measurements in both argon [128,129,130,131] and xenon [132,133,134]. A selection of these data have been used by the NEST collaboration to make a global fit for q ef f (E R ) [118,135]. In this work, we follow NEST and others and adopt a data-motivated model with the form…”

“…These parameters can depend on the strength of an applied electric field, which is relevant for dual-phase detectors. For xenon, the NEST collaboration quotes A q = 0.151 ± 0.027 and B q = 0.1 ± 0.05 at zero applied electric field [135] while the recent LUX analysis finds A q = 0.173 and B q = 0.05 over a range of applied fields between about 30-600 V/cm [136]. In the xenon analysis to follow we fix A q = 0.16 and B q = 0.08, assuming an E-field strength between 50-200 V/cm.…”

Detecting Beyond the Standard Model Interactions of Solar Neutrinos in Low-Threshold Dark Matter Detectors

“…We follow an analogous procedure to the semiconductor case for converting nuclear recoil energy into quantized charges. For liquid xenon and argon detectors, the NEST collaboration [46][47][48] has provided excellent simulated models for n e (E R ) down to energies ∼ 200 eV for nuclear recoils which we use to predict the charge yield from nuclear interactions. Below this 200 eV limit, we again extrapolate as a power-law to a spectrum of cut-off energies for nuclear recoils and plot the results in Fig.…”