Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field

TL;DR

This study demonstrates that the scintillation light yield from nuclear recoils in liquid argon significantly depends on the applied drift field, challenging previous assumptions used in dark matter detection sensitivity estimates.

Contribution

It provides the first direct measurement of how drift field influences scintillation from low-energy nuclear recoils in liquid argon.

Findings

Scintillation yield decreases with increasing drift field.

Significant dependence observed at 11 keV recoil energy.

Implications for dark matter search sensitivity estimates.

Abstract

We have exposed a dual-phase Liquid Argon Time Projection Chamber (LAr-TPC) to a low energy pulsed narrowband neutron beam, produced at the Notre Dame Institute for Structure and Nuclear Astrophysics to study the scintillation light yield of recoiling nuclei in a LAr-TPC. A liquid scintillation counter was arranged to detect and identify neutrons scattered in the LAr-TPC target and to select the energy of the recoiling nuclei. We report the observation of a significant dependence on drift field of liquid argon scintillation from nuclear recoils of 11 keV. This observation is important because, to date, estimates of the sensitivity of noble liquid TPC dark matter searches are based on the assumption that electric field has only a small effect on the light yield from nuclear recoils.