HERETIX: A Hermetic, Enriched, Rare-Event Time Projection Chamber in Xenon

Abstract

Xenon-based time projection chambers have established themselves as one of the most powerful technologies for rare-event searches. HERETIX is a proposed multi-tonne liquid xenon observatory featuring two nested time projection chambers that enable the simultaneous optimisation of searches for weakly interacting massive particles and neutrinoless double beta decay ($0\hat{I}½{\hat{I}}^2{\hat{I}}^2$) of ${}^{136}$Xe. A hermetically sealed sapphire vessel containing xenon enriched to 90% ${}^{136}$Xe forms the inner detector, providing an ultra-low-background environment for $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ searches. Monte Carlo studies indicate that material-induced backgrounds can be effectively eliminated, yielding a projected $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ half-life sensitivity of $3.2\times 10^{28}\mathrm{years}$ at 90% confidence level after a 10-year exposure, while the surrounding xenon volume, depleted in ${}^{136}$Xe, preserves the excellent dark matter sensitivity of large liquid xenon detectors. HERETIX therefore offers a unified experimental approach capable of delivering leading sensitivity to two of the most compelling questions in fundamental physics.

15 pages, 8 figures