Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of ${}^{136}$Xe

Abstract

The DARWIN observatory is a proposed next-generation experiment to search for particle dark matter and for the neutrinoless double beta decay of ${}^{136}$Xe. Out of its 50t total natural xenon inventory, 40t will be the active target of a time projection chamber which thus contains about 3.6 t of ${}^{136}$Xe. Here, we show that its projected half-life sensitivity is $2.4\times 10^{27}$yr, using a fiducial volume of 5t of natural xenon and 10yr of operation with a background rate of less than 0.2 events/(t$\cdot$yr) in the energy region of interest. This sensitivity is based on a detailed Monte Carlo simulation study of the background and event topologies in the large, homogeneous target. DARWIN will be comparable in its science reach to dedicated double beta decay experiments using xenon enriched in ${}^{136}$Xe.

12 pages, 9 figures