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

## TL;DR

This paper reports the first search for neutrinoless double beta decay of $^{136}$Xe using the PandaX-II liquid xenon detector, setting new limits on decay half-life and neutrino mass.

## Contribution

It presents the first neutrinoless double beta decay search results from a dual-phase xenon experiment, with optimized event selection and analysis.

## Key findings

- No evidence of neutrinoless double beta decay was observed.
- Lower limit on decay half-life is 2.4 x 10^{23} years.
- Effective Majorana neutrino mass is constrained to less than 1.3-3.5 eV.

## 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 $m_{\beta \beta} < (1.3 - 3.5)$ eV. This is the first NLDBD result reported from a dual-phase xenon experiment.