Detection prospects for the second-order weak decays of $^{124}$Xe in multi-tonne xenon time projection chambers

Understand

We investigate the detection prospects for two-neutrino and neutrinoless second order weak decays of $^{124}$Xe -- double electron capture ($0/2\nu\text{ECEC}$), electron capture with positron emission ($0/2\nu\text{EC}\beta^+$) and double-positron emission ($0/2\nu\beta^+\beta^+$) -- in multi-tonne xenon time projection chambers.

• We simulate the decays in a liquid xenon medium and develop a reconstruction algorithm which uses the multi-particle coincidence in these decays to separate signal from background.
• This is used to compute the expected detection efficiencies as a function of position resolution and energy threshold for planned experiments.
• In addition, we consider an exhaustive list of possible background sources and find that they are either negligible in rate or can be greatly reduced using our topological reconstruction criteria.