Searching for Neutrino-less Double Beta Decay of ${}^{136}$Xe with PandaX-II Liquid Xenon Detector

Abstract

We report the Neutrino-less Double Beta Decay (NLDBD) search results from PandaX-II dual-phase liquid xenon time projection chamber. The total live time used in this analysis is 403.1 days from June 2016 to August 2018. With NLDBD-optimized event selection criteria, we obtain a fiducial mass of 219 kg of natural xenon. The accumulated xenon exposure is 242 kg$\cdot$yr, or equivalently 22.2 kg$\cdot$yr of ${}^{136}$Xe exposure. At the region around ${}^{136}$Xe decay Q-value of 2458 keV, the energy resolution of PandaX-II is 4.2%. We find no evidence of NLDBD in PandaX-II and establish a lower limit for decay half-life of 2.4 $\times 10^{23}$ yr at the 90% confidence level, which corresponds to an effective Majorana neutrino mass $m_{{\hat{I}}^2{\hat{I}}^2}<(1.3-3.5)$ eV. This is the first NLDBD result reported from a dual-phase xenon experiment.

Submitted to Chinese Physics C