Enhanced search sensitivity to the double beta decay of 136Xe to excited states with topological signatures

Abstract

The double beta decay of 136Xe to excited states of 136Ba (DBD-ES) has not yet been discovered experimentally. The experimental signature of such decays, one or two gamma rays following the beta signals, can be identified more effectively in a gaseous detector with the help of topological signatures. We have investigated key parameters of particle trajectories of DBD-ES with Monte Carlo simulation data of the proposed PandaX-III detector as an example. The background rates can be reduced by about one order of magnitude while keeping more than half of signals with topological analysis. The estimated half-life sensitivity of DBD-ES can be improved by 1.8 times to 4.1×1023 year (90% C.L.). Similarly, the half-life sensitivity of neutrinoless double beta decay of 136Xe to excited states of 136Ba can be improved by a factor of 4.8 with topological signatures.