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The decay of the primordial isotopes 238U, 235U, 232Th, and 40K has contributed to the terrestrial heat budget throughout the Earth's history. Hence, the individual abundance of those isotopes are key parameters in reconstructing contemporary Earth models. The geoneutrinos produced by the radioactive decays of uranium and thorium have been observed with the Kamioka Liquid‐Scintillator Antineutrino Detector (KamLAND). Those measurements have been improved with more than 18‐year observation time, and improvement in detector background levels mainly with an 8‐year nearly reactor‐free period, which now permit spectroscopy with geoneutrinos. Our results yield the first constraint on both uranium and thorium heat contributions. The KamLAND result is consistent with geochemical estimations based on elemental abundances of chondritic meteorites and mantle peridotites. The High‐Q model is disfavored at 99.76% C.L. and a fully radiogenic model is excluded at 5.2σassuming a homogeneous heat producing element distribution in the mantle. The energy to drive the Earth's engine comes from two different sources: primordial and radiogenic. Primordial energy comes from the added heat by collisions of accreting material and less so by the energy accompanying the sinking of metal to form the core. The radioactive decays of heat producing elements (i.e., potassium, thorium, and uranium) also generate energy and some of these decaying elements produce antineutrinos (geoneutrinos). Geoneutrino measurements provide the Earth's fuel gauge for its radiogenic power supply and insights into the planet's cooling history. The measurement accuracy of the KamLAND experiment has been improved by an 18‐year long‐term observation and a reduction of the significant background generated by commercial reactors. Consequently, modern geoneutrino measurements have entered an era of distinct spectroscopic contributions coming from uranium and thorium. The KamLAND result is consistent with compositional models for the bulk silicate Earth (the crust plus the mantle) predicting low to medium radiogenic heat (10–20 TW (1012W)) and disfavor high concentration models (30 TW). This constraint sets the best limit on the permissible radiogenic energy budget in the Earth. Geoneutrino observations now begin to make significant contributions to the understanding of fundamental driving forces powering the Earth dynamic behavior. Geoneutrino measurement with low reactor neutrino backgrounds improves the distinct spectroscopic contributions of U and ThRadiogenic power in the Earth estimated from this geoneutrino measurement is consistent with a range of models and disfavors the higher power modelIdentifying the Earth's mantle contribution to the total geoneutrino flux strongly depends on an accurate estimation of the crustal contribution Geoneutrino measurement with low reactor neutrino backgrounds improves the distinct spectroscopic contributions of U and Th Radiogenic power in the Earth estimated from this geoneutrino measurement is consistent with a range of models and disfavors the higher power model Identifying the Earth's mantle contribution to the total geoneutrino flux strongly depends on an accurate estimation of the crustal contribution

The recent long-term shutdown of Japanese nuclear reactors has resulted in a significantly reduced reactor v̄e flux at KamLAND. This running condition provides a unique opportunity to confirm and constrain backgrounds for the reactor v̄e oscillation analysis. The data set also has improved sensitivity for other v̄e signals, in particular v̄e's produced in β-decays from 238U and 232Th within the Earth's interior, whose energy spectrum overlaps with that of reactor v̄e's. Including constraints on θ13 from accelerator and short-baseline reactor neutrino experiments, a combined three-flavor analysis of solar and KamLAND data gives fit values for the oscillation parameters of tan²θ12 = 0.436-0.025+0.029, Δm212 = 7.53-0.18+0.18 × 10-5 eV², and sin²θ13 = 0.023-0.002+0.002. Assuming a chondritic Th/U mass ratio, we obtain 116-27+28 v̄e events from 238U and 232Th, corresponding to a geo v̄e flux of 3.4-0.8 +0.8 × 106 cm- 2s- 1 at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo v̄e rate. [ABSTRACT FROM AUTHOR]

We present a search for the proton decay mode p → ...K+ based on an exposure of 8.97 kton-years in the KamLAND experiment. The liquid scintillator detector is sensitive to successive signals from → ...K+ with unique kinematics, which allow us to achieve a detection efficiency of 44%, higher than previous searches in water Cherenkov detectors. We find no evidence of proton decays for this mode. The expected background, which is dominated by atmospheric neutrinos, is 0.9 ± 0.2 events. The nonbackgroundsubtracted limit on the partial proton lifetime is τ/B(→ ...K+) > 5.4 x 1032 years at 90% C.L. [ABSTRACT FROM AUTHOR]

The KamLAND experiment is a very long baseline reactor νe oscillation experiment. This experiment has sensitivity to the oscillation parameters Δm2 > 10−5 eV2 and sin2 2θ > 0.2, using reactor νe which come typically from 170km away. This sensitive region completely covers the currently most favored MSW-LMA solution for the solar neutrino deficit problem. After 5 years of detector construction, the data taking started successfully in Jan. 2002. The detector performance is sufficient to perform reactor νe physics and we expect the first physics result will come out soon. In this paper, the KamLAND detector, its expected sensitivities, history, and recent progress since the time of the conference, are briefly described. [Copyright &y& Elsevier]