About half of the neutrinos detected from natural, underground sources come from the Earth’s mantle, rather than the crust, according to an analysis of new neutrino detection data.

“For those of us in the field, this is very impressive progress,” says Jason Detwiler of the University of Washington in Seattle, a member of the KamLAND group. “Their spectrum is very clean and beautifully and incontrovertibly demonstrates the presence of the geoneutrino signal.” Detwiler says that the number of mantle neutrinos seen by Borexino may have geophysical significance. ”The data are consistent with there being enough radiogenic heat to drive mantle convection,” he says, referring to the slow turnover of mantle material over geologic time.

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Agostini M., et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek, K. Jędrzejczak

See Focus story: Neutrinos Detected from the Earth’s Mantle

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http://dx.doi.org/10.1103/PhysRevD.92.031101

Abstract

We report an improved geoneutrino measurement with Borexino from 2056 days of data taking. The present exposure is (5.5±0.3)×1031  proton×yr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain 23.7+6.5−5.7(stat)+0.9−0.6(sys) geoneutrino events. The null observation of geoneutrinos with Borexino alone has a probability of 3.6×10−9 (5.9σ). 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.

L. Ludhova, (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek

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http://dx.doi.org/10.1134/S1063779615020148

Abstract

Geo-neutrinos, electron anti-neutrinos produced in β-decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet’s interior. After a brief introduction about the Earth, the geo-neutrinos’ properties and the main aims of their study are discussed. An overview of the latest experimental results obtained by the Borexino collaboration is provided, followed by a short overview of future perspectives of this new inter-disciplinary field.

Download: http://dx.doi.org/10.1016/j.physletb.2013.04.030

Abstract

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(3.69±0.16)×1031 proton × year after all selection cuts and background subtraction, we detected (14.3±4.4)(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) TNUSgeo=(38.8±12.0) TNU with just a 6×10−66×10−6 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) TNUSTh=(10.6±12.7) TNU and SU=(26.5±19.5) TNUSU=(26.5±19.5) TNU. Borexino data alone are compatible with a mantle geo-neutrino signal of (15.4±12.3) TNU(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(14.1±8.1) TNU. Our measurement of View the MathML source31.2−6.1+7.0 reactor anti-neutrino events is in agreement with expectations in the presence of neutrino oscillations.