KamLAND Experiment

KamLAND stands for "Kamioka Liquid Scintillator Anti-Neutrino Detector". KamLAND is the largest scintillation detector ever constructed. Apart from measuring reactor anti-neutrinos, the KamLAND experiment has sensitivity to detect electron anti-neutrinos produced by the decay of 238U and 232Th within the Earth (so-called geoneutrinos). Earth composition models suggest that the total radiogenic power due to these decays is 16TW, approximately half of the measured heat dissipation rate from the Earth. KamLAND has searched for these geoneutrinos and, assuming a Th/U mass concentration ratio of 3.9, finds that the 90% C.L. for the total number of detected geoneutrinos is 4.5 to 54.2. This result is consistent with the central value of 19 events predicted by geophysical models. While the present data has limited statistical power, it nevertheless provides an upper limit of 60TW for the radiogenic power of U and Th in the Earth, a quantity that is currently poorly constrained.