Precision Background Determination for Solar Neutrino Detection in Low-Background Xenon Experiments

Basic data for this project

Description

Next-generation low-background dark matter experiments, such as DARWIN/XLZD, which utilize xenon targets in a time projection chamber detector, will also be capable of measuring proton-proton chain solar neutrinos via elastic electron scattering. The projected improvement in sensitivity will allow constraints on the solar neutrino flux down to a sub-percentage level. A key factor in achieving this high sensitivity is the ability in minimizing the impact of the electron-recoil background. The major contributors are radioactive isotopes of krypton and radon, as well as trace radioactive elements found in detector materials. To address this, novel distillation columns are being developed at the University of Muenster, targeting continuous krypton removal for the first time and setting new benchmarks for radon reduction in xenon. On the other hand, the Rare Gas Mass Spectrometer (RGMS) at the Max-Planck-Institute for Nuclear Physics (MPIK) has achieved the world's best krypton detection limit. To enhance the robustness of these measurements, an upgrade to fully automatize RGMS (Auto-RGMS) is under development. The objective of this proposal is to improve the detection limits for all major electron-recoil background components by an order of magnitude. This objective requires overcoming unique challenges for each background source. For Krypton, the project introduces the Xenon Filter for Krypton detection Enhancement (XeFKrE) system, designed to enhance the RGMS detection limits by increasing the sample capacity. For radon, the project aims to develop a novel analytical method to determine the background level via alpha decays while accounting for the loss effect due to detector configuration. For detector materials, the project proposes to examine efficient simulation methods to track events within the region of interest via machine learning. Finally, a combined study will assess how each background determination improves the overall sensitivity to solar neutrinos. Software advancement from this project will be derived using data, simulation, and sensitivity study tools from the analysis framework of the XENONnT experiment. To achieve the objective, the project draws on a comprehensive suite of tools, ranging from the construction of detection systems to innovations in analysis and simulation. Central to this proposal is the synergy between developments at the University of Muenster and MPIK, which creates an ideal opportunity for this project. The techniques established through this project will offer invaluable resources for all low-background experiments. Ultimately, the results of this project will fully unlock the potential for precision studies of solar neutrino physics in next-generation experiments.