Background reduction in 136Xe double-beta-decay experiments through direct barium-ion detection

Abstract

Tagging barium ions in double-beta decay experiments involving 136 Xe atoms 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, I present a detection scheme that relies exclusively on the intrinsic energy levels of the barium ion. This method is based solely on the optical interrogation of its electronic transitions, avoiding the need for additional additives or fluorescent agents in the xenon vessel and thereby simplifying the experimental setup. Throughout the manuscript, I demonstrate the feasibility of this detection concept through numerical simulations under realistic experimental conditions inspired by the Neutrino Experiment with a Xenon TPC experiment. The results show that the fluorescence signature of the barium ion can be reliably detected, indicating that the proposed method is a viable path toward background-free searches for neutrinoless double-beta decay.