were used to limit the U/Th radiopower to under 60TW. Combination results with Borexino were published in 2011, measuring the U/Th heat flux. New results in 2013, benefiting from the reduced backgrounds due to Japanese reactor shutdowns, were able to constrain U/Th radiogenic heat production to TW using 116 events. This constrains composition models of the bulk silicate Earth and agrees with the reference Earth model. KamLAND-Zen Double Beta Decay Search KamLAND-Zen uses the detector to study beta decay of 136Xe from a balloon placed in the scintillator in summer 2011. Observations set a limit for neutrinoless double-beta decay half-life of . A double beta decay lifetime was also measured: yr, consistent with other xenon studies. KamLAND-Zen plans continued observations with more enriched Xe and improved detector components. An improved search was published in August 2016, increasing the half-life limit to , with a neutrino mass bound of 61–165 meV. The first KamLAND-Zen apparatus, KamLAND-Zen 400, completed two research programs, Phase I (2011 Oct. - 2012 Jun.) and Phase II (2013 Dec. - 2015 Oct.). The combined data of Phase I and II implied the lower bound years for the neutrinoless double beta decay half-life. The KamLAND-Zen 400 operated from 2011 October to 2015 October and was then replaced by KamLAND-Zen 800. The second KamLAND-Zen experiment apparatus, KamLAND-Zen 800, with bigger balloon of about 750 kg of Xenon was installed in the KamLAND detector 10 May 2018. The operation was expected to start winter 2018-2019 with 5 years of expected operation. The KamLAND-Zen 800 experiment started data taking in January 2019 and first results were published in 2020. In March 2022 the KamLAND-Zen Collaboration using the KamLAND-Zen 800 published results about neutrinoless double-beta decay in Xe-136 using data collected between February 5, 2019 and May 8, 2021. No neutrinoless double-beta decay was observed, and the established lower bound for half-life was T > 2.3×10^{26} yr corresponding to upper limits on the effective Majorana neutrino mass of 36 – 156 meV. The KamLAND-Zen collaboration is planning to construct another apparatus, KamLAND2-Zen in the long term. References Further reading External links KamLAND official website KamLAND at Lawrence Berkeley National Laboratory (Berkeley Lab) KamLAND experiment record on INSPIRE-HEP Particle experiments Neutrino observatories Reactor neutrino experiments