The recent geoneutrino experimental results from KamLAND (Kamioka Liquid Scintillator Antineutrino Detector) and Borexino detectors reveal the usefulness of analyzing the Earth's geoneutrino flux, as it provides a constraint on the strength of the radiogenic heat power, and this, in turn, provides a test of compositional models of the bulk silicate Earth (BSE). This flux is dependent on the amount and distribution of heat‐producing elements (HPEs: U, Th, and K) in the Earth's interior. We have developed a geophysically based, three‐dimensional global reference model for the abundances and distributions of HPEs in the BSE. The structure and composition of the outermost portion of the Earth, the crust and underlying lithospheric mantle, are detailed in the reference model; this portion of the Earth has the greatest influence on the geoneutrino fluxes. The reference model combines three existing geophysical models of the global crust and yields an average crustal thickness of 34.4 ± 4.1 km in the continents and 8.0 ± 2.7 km in the oceans, and a total mass (in 10²² kg) of oceanic, continental, and bulk crust is 0.67 ± 0.23, 2.06 ± 0.25, and 2.73 ± 0.48, respectively. In situ seismic velocity provided by CRUST 2.0 allows us to estimate the average composition of the deep continental crust by using new and updated compositional databases for amphibolite and granulite facies rocks in combination with laboratory ultrasonic velocities measurements. An updated xenolithic peridotite database is used to represent the average composition of continental lithospheric mantle. Monte Carlo simulation is used to predict the geoneutrino flux at 16 selected locations and to track the asymmetrical uncertainties of radiogenic heat power due to the log‐normal distributions of HPE concentrations in crustal rocks.

We predict geoneutrino fluxes in a reference model based on a detailed description of Earth’s crust and mantle and using the best available information on the abundances of uranium, thorium, and potassium inside Earth’s layers. We estimate the uncertainties of fluxes corresponding to the uncertainties of the element abundances. In addition to distance integrated fluxes, we also provide the differential fluxes as a function of distance from several sites of experimental interest. Event yields at several locations are estimated and their dependence on the neutrino oscillation parameters is discussed. At Kamioka we predict $N(\mathrm{U}+\mathrm{Th})=35\mathrm{}\pm 6$ events for ${10}^{32}\mathrm{proton}\mathrm{yr}$ and 100% efficiency assuming ${\sin }^2\left(2\mathrm{}\theta \right)=0.863\mathrm{}$ and $\delta m^2=7.3\mathrm{}\times {10}^{-5}{\mathrm{eV}}^2.$ The maximal prediction is 55 events, obtained in a model with fully radiogenic production of the terrestrial heat flow.

We present a measurement of the geo-neutrino signal obtained from 1353 days of data with the Borexino detector at Laboratori Nazionali del Gran Sasso in Italy. With a fiducial exposure of (3.69±0.16)×1031 proton × year after all selection cuts and background subtraction, we detected (14.3±4.4) geo-neutrino events assuming a fixed chondritic mass Th/U ratio of 3.9. This corresponds to a geo-neutrino signal Sgeo=(38.8±12.0) TNU with just a 6×10-6 probability for a null geo-neutrino measurement. With U and Th left as free parameters in the fit, the relative signals are STh=(10.6±12.7) TNU and SU=(26.5±19.5) TNU. Borexino data alone are compatible with a mantle geo-neutrino signal of (15.4±12.3) TNU, while a combined analysis with the KamLAND data allows to extract a mantle signal of (14.1±8.1) TNU. Our measurement of 31.2-6.1+7.0 reactor anti-neutrino events is in agreement with expectations in the presence of neutrino oscillations

We report an improved geoneutrino measurement with Borexino from 2056 days of data taking. The present exposure is $(5.5\pm 0.3)\times {10}^{31}\mathrm{proton}\times \mathrm{yr}$. Assuming a chondritic Th/U mass ratio of 3.9, we obtain ${23.7}_{-5.7}^{+6.5}(\text{stat}{)}_{-0.6}^{+0.9}(\text{sys})$ geoneutrino events. The null observation of geoneutrinos with Borexino alone has a probability of $3.6\times {10}^{-9}$ ($5.9\sigma$). A geoneutrino signal from the mantle is obtained at 98% C.L. The radiogenic heat production for U and Th from the present best-fit result is restricted to the range 23–36 TW, taking into account the uncertainty on the distribution of heat producing elements inside the Earth.