A comprehensive study of low-energy response for xenon-based dark matter experiments

Abstract

We report a comprehensive study of the energy response to low-energy recoils in dual-phase xenon-based dark matter experiments. A recombination model is developed to explain the recombination probability as a function of recoil energy at zero field and non-zero field. The role of e-ion recombination is discussed for both parent recombination and volume recombination. We find that the volume recombination under non-zero field is constrained by a plasma effect, which is caused by a high density of charge carriers along the ionization track forming a plasma-like cloud of charge that shields the interior from the influence of the external electric field. Subsequently, the plasma time that determines the volume recombination probability at non-zero field is demonstrated to be different between electronic recoils and nuclear recoils due to the difference of ionization density between two processes. We show a weak field-dependence of the plasma time for nuclear recoils and a stronger field-dependence of the plasma time for electronic recoils. As a result, the timedependent recombination is implemented in the determination of charge and light yield with a generic model. Our model agrees well with the available experimental data from xenon-based dark matter experiments.

Dark matter direct-detection experiments

“…In [256][257] and [258], the scintillation and ionisation for liquid noble-gas detector are modelled. The former includes scintillation quenching from the Birks [260] model while the latter two incorporate measured data into the description (see also the recent study [259]).…”

Emission of Single and Few Electrons in XENON1T and Limits on Light Dark Matter

“…Our detector response model can thus be considered to be conservative. We do not proceed with an extension of the S2-only analysis for a SI WIMP-nucleon interaction although suggestions do exist about various extrapolations below the lower-energy NR charge yield measurement [41,42].…”

Discrimination of nuclear and electronic recoil events using plasma effect in germanium detectors

“…The anti-correlation between the charge and light yield clearly demonstrates the recombination probability as a function of the plasma time [18].…”

“…Note that the plasma effect, in general, can be observed by measuring the plasma time and the amplitude distortion of the pulse shape due to the recombination of charge carriers induced by plasma time. However, the lifetime of electrons in germanium at 77 Kelvin is above 10 −4 seconds, the recombination of charge carriers within the plasma time of less than 100 nanoseconds is negligible according to the recombination probability function developed in [18].…”

“…In the dual-phase xenon detectors for the direct detection of dark matter [15][16][17], the plasma time plays an important role in the recombination of electron-ion pairs [18] as a function of recoil energy, type, and electric field. The anti-correlation between the charge and light yield clearly demonstrates the recombination probability as a function of the plasma time [18].…”