Event Reconstruction in a Liquid Xenon Time Projection Chamber with an Optically-Open Field Cage

Understand

nEXO is a proposed tonne-scale neutrinoless double beta decay ($0\nu\beta\beta$) experiment using liquid ${}^{136}Xe$ (LXe) in a Time Projection Chamber (TPC) to read out ionization and scintillation signals.

• Between the field cage and the LXe vessel, a layer of LXe ("skin" LXe) is present, where no ionization signal is collected.
• Only scintillation photons are detected, owing to the lack of optical barrier around the field cage.
• In this work, we show that the light originating in the skin LXe region can be used to improve background discrimination by 5% over previous published estimates.