Status of the KamLAND experiment

Thomas O'Donnell


KamLAND is a one kiloton liquid scintillator detector which studies neutrino oscillation with reactor-antineutrinos at an average baseline of 180km. The experiment was the first to report reactor-antinuetrinodisappearance consistent with the neutrino mass splitting favored by the LMA-MSW solution to the Solar Neutrino Problem. Furthermore, KamLAND observed distortion of the reactor spectrum -- the fingerprint of mass-driven flavor oscillation -- and is uniquely sentitive to the mass splitting $\Delta m^{2}_{21}$. In this talk I will describe the experiment and present the results of the most recent data set which amounts to a total exposure of $3.49 \times 10^{32}$ proton-years and includes data collected with more favorable background conditions achieved by a detector radiopurity upgrade. Under the assumption of CPT invariance, a three-flavor analysis combining KamLAND and solar data yields best-fit values of the oscillation parameters: $\Delta m^{2}_{21} = 7.50^{+0.19}_{-0.20} \times 10^{-5} \rm{eV}^{2}$, $\tan^{2} \theta_{12} = 0.452^{+0.035}_{-0.033}$, and weak constraints on $\theta_{13}$.

Finally, as the current phase of data taking draws to an end, I will briefly describe KamLAND-Zen --- a plan to repurpose the detector to search for neutrino-less double beta decay of $^{136}$Xe.