Searching for Two-Neutrino and Neutrinoless Double Beta Decay of Xe134 with the PandaX-4T Experiment

Xe134 is a candidate isotope for neutrinoless double beta decay (0νββ) search. In addition, the two-neutrino case (2νββ) allowed by the standard model of particle physics has not yet been observed. With the 656-kg natural xenon in the fiducial volume of the PandaX-4T detector, which contains 10.4% of Xe134, and its initial 94.9-day exposure, we have established the most stringent constraints on 2νββ and 0νββ of Xe134 half-lives, with limits of 2.8×1022 yr and 3.0×1023 yr at 90% confidence level, respectively. The 2νββ (0νββ) limit surpasses the previously reported best result by a factor of 32 (2.7), highlighting the potential of large monolithic natural xenon detectors for double beta decay searches.Received 2 January 2024Accepted 15 March 2024DOI:https://doi.org/10.1103/PhysRevLett.132.152502© 2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDouble beta decayNeutrinoless double beta decayParticles & Fields