Measurement of the liquid argon energy response to nuclear and electronic recoils

Abstract

A liquid argon time projection chamber, constructed for the Argon Response to Ionization and Scintillation (ARIS) experiment, has been exposed to the highly collimated and quasi-monoenergetic LICORNE neutron beam at the Institute de Physique Nuclaire Orsay in order to study the scintillation response to nuclear and electronic recoils. An array of liquid scintillator detectors, arranged around the apparatus, tag scattered neutrons and select nuclear recoil energies in the [7, 120] keV energy range. The relative scintillation efficiency of nuclear recoils was measured to high precision at null field, and the ion-electron recombination probability was extracted for a range of applied electric fields. Single-scattered Compton electrons, produced by gammas emitted from the de-excitation of 7 Li * in coincidence with the beam pulse, along with calibration gamma sources, are used to extract the recombination probability as a function of energy and electron drift field. The ARIS results have been compared with three recombination probability parameterizations (Thomas-Imel, Doke-Birks, and PARIS), allowing for the definition of a fully comprehensive model of the liquid argon response to nuclear and electronic recoils down to a few keV range. The constraints provided by ARIS to the liquid argon response at low energy allow the reduction of systematics affecting the sensitivity of dark matter search experiments based on liquid argon.

Calibration of liquid argon detector with 83mKr and 22Na in different drift fields

“…The difference of quenching factor is because of the recombination probability decreases with the increase of the particle energy in the range of 40keV to 511keV, which is consistent with Ref. [30].…”

Scintillation and ionization ratio of liquid argon for electronic and nuclear recoils at drift-fields up to 3 kV/cm

“…It is well known that the S1 and S2 light yields depend on the strength of electric field, imposed in drift interaction region, mainly due to recombination effect of ionizing electrons. Such properties are well measured by previous experiments, such as SCENE [6] (0-0.97 kV/cm, 10.3-57.3 keV nr , nr : nuclear recoil) and ARIS [7] (0-0.5 kV/cm, 7.1-117.8 keV nr ) where drift-fields are lower than 1 kV/cm and the ER/NR discrimination power of S2/S1 is not explicitly described. In this paper, we focus on the drift-field dependence of S2/S1 properties up to 3.0 kV/cm.…”

“…For other parameter settings, we compare case 2 (δ = 0.61) and case 3 (α = 0.21 [16]) as a source of systematic uncertainty for the ER/NR discrimination power estimation described in the next section. 18.5 ± 9.7 Table 1: Three cases of δ and α parameter setting and fitting results of γ extracted by SCENE data with a comparison to the ARIS result [7].…”

First constraint on coherent elastic neutrino-nucleus scattering in argon

“…Argon has been widely used for both dark matter WIMP searches [25,26] and for neutrino detection [27] and has therefore been well characterized above 20 keV in the literature. It has a high light yield, 40 photons=keVee [28] (electron equivalent energy deposition), providing a sufficiently low threshold for CEvNS detection, and the quenched response to nuclear recoils has been well-characterized [29][30][31][32] allowing for well-understood CEvNS predictions. LAr scintillates on two significantly different timescales (τ singlet ≈6ns;τ triplet ≈ 1600 ns) [33] providing powerful pulse-shape discrimination (PSD) capabilities to separate nuclear from electronic recoils (NR and ER respectively) [34][35][36].…”