Electron recombination in low-energy nuclear recoils tracks in liquid argon

TL;DR

This study uses computer simulations to analyze electron-ion recombination in liquid argon nuclear recoil tracks, reproducing experimental ionization yields and revealing fast static recombination effects that impact detector responses.

Contribution

It introduces realistic electron transport models to simulate recombination in liquid argon, providing new insights into fluctuation estimates and recombination kinetics for nuclear recoils.

Findings

Reproduces experimental ionization yields for 6.7 keV nuclear recoils.

Identifies significant fast static recombination affecting electron escape.

Estimates recombination fluctuations deviating from binomial distribution.

Abstract

This paper presents an analysis of electron-ion recombination processes in ionization tracks of recoiled atoms in liquid argon (LAr) detectors. The analysis is based on the results of computer simulations which use realistic models of electron transport and reactions. The calculations reproduce the recent experimental results of the ionization yield from 6.7 keV nuclear recoils in LAr. The statistical distribution of the number of electrons that escape recombination is found to deviate from the binomial distribution, and estimates of recombination fluctuations for nuclear recoils tracks are obtained. A study of the recombination kinetics shows that a significant part of electrons undergo very fast static recombination, an effect that may be responsible for the weak drift-field dependence of the ionization yield from nuclear recoils in some noble liquids. The obtained results can be useful in the search for hypothetical dark matter particles and in other studies that involve detection of recoiled nuclei.