Measurement of the ionization yield of nuclear recoils in liquid argon at 80 and 233 keV

TL;DR

This study measures the ionization yield of nuclear recoils in liquid argon at 80 and 233 keV, providing crucial calibration data for dark matter and neutrino detection experiments.

Contribution

First measurement of ionization yield for nuclear recoils in liquid argon at higher energies using a two-phase Cryogenic Avalanche Detector.

Findings

Ionization yield at 80 keV: 7.8±1.1 e-/keV

Ionization yield at 233 keV: 9.7±1.3 e-/keV

Jaffe model better describes energy dependence than Thomas-Imel

Abstract

The energy calibration of nuclear recoil detectors is of primary importance to rare-event experiments such as those of direct dark matter search and coherent neutrino-nucleus scattering. In particular, such a calibration is performed by measuring the ionization yield of nuclear recoils in liquid Ar and Xe detection media, using neutron elastic scattering off nuclei. In the present work, the ionization yield for nuclear recoils in liquid Ar has for the first time been measured in the higher energy range, at 80 and 233 keV, using a two-phase Cryogenic Avalanche Detector (CRAD) and DD neutron generator. The ionization yield in liquid Ar at an electric field of 2.3 kV/cm amounted to 7.8+/-1.1 and 9.7+/-1.3 e-/keV at 80 and 233 keV respectively. The Jaffe model for nuclear recoil-induced ionization, in contrast to that Thomas-Imel, can probably consistently describe the energy dependence of the ionization yield.