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

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.

Directional modulation of electron-ion pairs recombination in liquid argon

“…It is usually assumed that, prior to thermalization, recombination is prevented. A recent study of the microscopic interactions [11] has criticized this assumption and provided evidence of a static recombination, taking place for a limited fraction of electron-ion pairs on a time scale shorter than that of thermalization. However, for the purpose of our study, this static recombination results in a rescaling of the total initial charge, without affecting the recombination dependence upon the external electric field and the crucial dependence upon the angle between track and drift field.…”