We present results from the KamLAND-Zen double-beta decay experiment based on an exposure of 77.6 days with 129 kg of $^{ 136}$Xe. The measured two-neutrino double-beta decay half-life of $^{ 136}$Xe is $T_{ 1/2}^{ 2\nu} = 2.38 \pm 0.02(stat) \pm 0.14(syst) \times 10^{ 21}$ yr, consistent with a recent measurement by EXO-200. We also obtain a lower limit for the neutrinoless double-beta decay half-life, $T_{ 1/2}^{ 0\nu} > 5.7 \times 10^{ 24}$ yr at 90% confidence level (C.L.), which corresponds to almost a five-fold improvement over previous limits.
Categories: hep-ex nucl-ex
