Background reduction in $^{136}$Xe double beta decay experiments through direct barium ion detection

Abstract: Tagging barium ions in double beta decay experiments involving $^{136}$Xe offers a promising pathway to achieving an almost background-free environment, which is essential for addressing key unresolved questions in neutrino physics, such as the nature of neutrinos and their mass hierarchy. In this manuscript, we present a novel detection scheme that relies exclusively on the intrinsic energy levels of the barium ion. This method eliminates the need for additional additives in the xenon vessel, thereby simplifying the experimental setup and enhancing the potential sensitivity of the experiment.