KamLAND-Zen searches for neutrinoless double beta decay with $^{136}$Xe loaded liquid scintillator.
After the successful completion of KamLAND-Zen 400, KamLAND-Zen 800 started data taking in 2019 with almost double the amount of xenon and a low radioactive LS container. With an exposure of 970 kg-yr of $^{136}$Xe and various improvements for the analysis method, we set a lower limit for $^{136}$Xe $0\nu\beta\beta$ half-life on $T^{0\nu}_{1/2} > 2.0 \times 10^{26}$ yr at 90\% C.L.
KamLAND-Zen 400 data set is also reanalyzed with a new analysis scheme, and we obtain a combined limit for half-life on $T^{0\nu}_{1/2} > 2.3 \times 10^{26}$ yr at 90\% C.L. Corresponding upper limits on the effective Majorana neutrino mass is 36 – 156 meV.