Neutral bremsstrahlung electroluminescence in noble liquids

TL;DR

This paper extends the concept of neutral bremsstrahlung electroluminescence from noble gases to noble liquids, calculating photon yields and spectra to aid in the development of detectors for dark matter and neutrino research.

Contribution

It introduces a theoretical framework for neutral bremsstrahlung electroluminescence in noble liquids and provides the first calculations of photon yields and spectra in these liquids.

Findings

Photon yields for NBrS EL in noble liquids calculated for the first time.

Spectral characteristics of NBrS EL in noble liquids determined.

Implications for noble liquid detector development discussed.

Abstract

Proportional electroluminescence (EL) is the physical effect used in two-phase dark matter detectors, to optically record in the gas phase the ionization signal produced by particle scattering in the liquid phase. In our previous works the presence of a new EL mechanism in noble gases, namely that of neutral bremsstrahlung (NBrS), was demonstrated both theoretically and experimentally, in addition to the ordinary EL mechanism due to excimer emission. In this work we show that the similar theoretical approach can apply to noble liquids, namely to liquid helium, neon, argon, krypton and xenon. In particular, the photon yields and spectra for NBrS EL in noble liquids have for the first time been calculated, using the electron energy and transport parameters obtained in the framework of Cohen-Lekner and Atrazhev theory. The relevance of the results obtained to the development of noble liquid detectors for dark matter searches and neutrino experiments is discussed.