Scintillation and Ionization Ratio of Liquid Argon for Electronic and Nuclear Recoils at Drift-Fields up to 3 kV/cm

TL;DR

This paper investigates the ionization and scintillation ratio in liquid argon for different recoil types at various electric fields, enhancing understanding crucial for dark matter detection.

Contribution

It provides new measurements of the S2/S1 ratio in liquid argon at drift fields up to 3 kV/cm, which was previously less well characterized.

Findings

S2/S1 ratio varies with drift field and recoil type.

Discrimination power against electron recoil improves with optimized electric fields.

Results support liquid argon as a viable medium for dark matter experiments.

Abstract

A two-phase argon detector has high discrimination power between electron recoil and nuclear recoil events based on the pulse shape discrimination and the ionization/scintillation ratio (S2/S1). This character is very suitable for the dark matter search to establish the low background experiment. However, the basic properties of S2/S1 of argon are not well known, as compared with xenon. We report the evaluation of S2/S1 properties with a two-phase detector at drift-fields of 0.2-3.0 kV/cm. Finally, the discrimination power against electron recoil background of S2/S1 is discussed.