Measurement of the ionization yield from nuclear recoils in liquid xenon between 0.3 -- 6 keV with single-ionization-electron sensitivity

Abstract

Dual-phase xenon TPC detectors are a highly scalable and widely used technology to search for low-energy nuclear recoil signals from WIMP dark matter or coherent nuclear scattering of ∼MeV neutrinos. Such experiments expect to measure O(keV) ionization or scintillation signals from such sources. However, at ∼ 1 keV and below, the signal calibrations in liquid xenon carry large uncertainties that directly impact the assumed sensitivity of existing and future experiments. In this work, we report a new measurement of the ionization yield of nuclear recoil signals in liquid xenon down to 0.3 keV -the lowest energy calibration reported to date -at which energy the average event produces just 1.1 ionized electrons. Between 2 and 6 keV, our measurements agree with existing measurements, but significantly improve the precision. At lower energies, we observe a decreasing trend that deviates from simple extrapolations of existing data. We also study the dependence of ionization yield on the applied drift field in liquid xenon between 220V/cm and 6240V/cm, allowing these measurements to apply to a broad range of current and proposed experiments with different operating parameters.

Astrophysical constraints on non-standard coherent neutrino-nucleus scattering

“…Recently Ref. [95] highlighted the possibility of reducing the energy threshold in dual phase xenon detectors to 0.3 keV. In this case, our bounds would improve significantly (up to ∼ 50%).…”

Enhancing the sensitivity of the LUX-ZEPLIN (LZ) dark matter experiment to low energy signals

“…As the S1 coincidence level is lowered, so is the energy threshold of the detector. At present, the ionization yield of NR in LXe is known for recoil energies as low as 0.3 keV [31]. We use the NEST [32] parametrization of LXe yields for all energies, but we impose a model cutoff at 0.3 keV, and assume NEST predictions for the light yield-based on low energy measurements down to 1.08 keV [33].…”

First ground-level laboratory test of the two-phase xenon emission detector RED-100

“…Regardless of the origin, these signals may be used for calibration of the detector response to the smallest ionization. This is of particular importance taking into account the fact that the signal from the coherent elastic scattering of reactor antineutrino off Xe atomic nucleus has a value of only a few ionization electrons [44].…”

“…A non-point-like cut is applied both to the accidental coincidence and CEnNS events. The CEnNS signal was estimated with the use of the latest NEST 2.01 version based on the recent measurement of ionization yield for xenon nuclear recoils in the sub-keV energy range [44]. Note, that this measurement has shown the much lower ionization yield than that predicted for the sub-keV energy range by the previous NEST 2.0 version based on the LUX data [56] and used by us in our previous publication.…”