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 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 ^{136}Xe. Here, we show that its projected half-life sensitivity is 2.4times {10}^{27},{hbox {year}}, using a fiducial volume of 5 t of natural xenon and 10 year of operation with a background rate of less than 0.2 events/(t cdot year) 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.
Highlights
Neutrinos are the only known elementary particles that are Majorana fermion candidates, implying that they would be their own antiparticles
The DARWIN observatory will reach a sensitivity to the neutrinoless double beta decay of 136Xe of 2.4 × 1027 years T1/2 exclusion limit (90% confidence level (CL)) and a discovery sensitivity (3 σ ) of T1/2 = 1.1 × 1027 years after 10 years of exposure
The external background could be reduced by a factor of three or more
Summary
Neutrinos are the only known elementary particles that are Majorana fermion candidates, implying that they would be their own antiparticles. The most sensitive probe for the Majorana nature of neutrinos is an extremely rare nuclear decay process called neutrinoless double beta decay (0νββ), where a nucleus with mass number A and charge Z decays by emitting only two electrons and changes its charge by two units (A,Z)−→(A,Z+2) + 2e−. We demonstrate that DARWIN has a similar reach to dedicated future neutrinoless double beta decay experiments This is due to its large, homogeneous target, and its ultra-low background, coupled to the capability of the TPC to simultaneously measure the location, energy, particle type and multiplicity of an event [12].
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