Neutrinoless double beta decay experiment N<italic>ν</italic>DEx based on a high pressure ⁸²SeF₆ gas time projection chamber

Abstract

<p indent="0mm">If the neutrinoless double beta (0<italic>νββ</italic>) decay is observed experimentally, it will have a revolutionary impact on particle physics. This discovery would demonstrate that the neutrino is its own antiparticle, aid in determining the absolute mass of the neutrino, explore the origin of its mass, and potentially explain the asymmetry between matter and antimatter in the universe through lepton number violation. We propose to develop a time projection chamber (TPC) utilizing high-pressure ⁸²SeF₆ gas as the detection medium, and employ a low-noise CMOS chip for readout to measure the 0<italic>νββ</italic> decay of ⁸²Se at the China Jinping Underground Laboratory (CJPL), referred to as the N<italic>ν</italic>DEx experiment. The decay nucleus ⁸²Se used in the experiment has a high <italic>Q_ββ</italic> value <sc>(2.996 MeV).</sc> The CMOS chip reads out the ionization signal without physical amplification, achieving extremely low noise and an energy resolution of approximately 1%; the excellent track detection capability of the TPC helps to eliminate background events; CJPL is currently the deepest underground laboratory in the world, with the surrounding rock layer providing effective shielding against cosmic ray background. With these advantages, the N<italic>ν</italic>DEx experiment has significant potential to achieve very low background levels and high experimental sensitivity. N<italic>ν</italic>DEx-100, the N<italic>ν</italic>DEx experiment containing <sc>100 kg</sc> of SeF₆ gas, is currently under development and is scheduled for installation at CJPL around 2025. This article will introduce the 0<italic>νββ</italic> physics motivation, the N<italic>ν</italic>DEx concept and its advantages, the conceptual design and current status of N<italic>ν</italic>DEx-100, as well as its background and sensitivity estimates.</p>

References