Barium Tagging with Selective, Dry-Functional, Single Molecule Sensitive On-Off Fluorophores for the NEXT Experiment

Abstract

In the search for neutrinoless double beta decay, understanding and reducing backgrounds is crucial for success. An advance that could drive backgrounds to negligible levels would be the ability to efficiently detect the barium daughter in ${}^{136}$Xe to ${}^{136}$Ba double beta decay, since no conventional radioactive process can produce barium ions or atoms in xenon at significant rates. In xenon gas, the barium daughter most likely survives as a dication. An approach under development by the NEXT collaboration involves transporting this ion from the active medium onto a coated transparent plane supporting a barium-sensitive fluorescent dye, monitored via fluorescence microscopy. Upon exposure to a barium dication, the dye will begin fluorescing, which, when correlated with the detection of a double electron signal at the anode, would confirm double beta decay.Our results have shown that a single barium ion can be resolved via Single Molecule Fluorescent Imaging (SMFI). The next challenge is a realization of this technique within in a large volume of xenon gas. Significant advances have recently been made: custom barium-tagging molecules that fluoresce strongly in the dry state when exposed to barium have been demonstrated, and devices constructed that can observe fluorescence via in-vacuum or in-gas Total Internal Reflection Fluorescence Microscopy. We present the status of this technique and the outlook for barium tagging with On-Off switchable fluorophores, including new results with a Ba${}^{2+}$-selective dye that functions under our desired conditions in the visible region and with single ion sensitivity.

arXiv comment9 Pages, 5 Figures, Conference Proceeding for the 2019 Meeting of the Division of Particles and Fields of the American Physical Society, July 29 to August 2, 2019, Northeastern University, Boston, C1907293

References in corpus (7)

• Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen
• Theory of neutrinoless double beta decay
• Neutrinoless double-beta decay. A brief review
• Demonstration of Single Barium Ion Sensitivity for Neutrinoless Double Beta Decay using Single Molecule Fluorescence Imaging
• Energy calibration of the NEXT-White detector with 1% resolution near Q${}_{\beta \beta }$ of ${}^{136}$Xe
• Mobility and Clustering of Barium Ions and Dications in High Pressure Xenon Gas
• Towards a background-free neutrinoless double beta decay experiment based on a fluorescent bicolor sensor