Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of 136 Xe

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 50 t total natural xenon inventory, 40 t will be the active target of a time projection chamber which thus contains about 3.6 t of 136Xe. Here, we show that its projected half-life sensitivity is 2.4 × 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 · yr) in the energy region of interest. This sensitivity is based on a detailed Monte Carlo simula- tion study of the background and event topologies in the large, homogeneous target. DARWIN will be com- parable in its science reach to dedicated double beta decay experiments using xenon enriched in 136Xe.