Measurement of geo-neutrinos from 1353 days of Borexino

TL;DR

This paper reports a measurement of geo-neutrinos using 1353 days of Borexino data, providing insights into Earth's interior composition and confirming reactor anti-neutrino signals consistent with neutrino oscillation models.

Contribution

First measurement of geo-neutrino signal with Borexino over 1353 days, including mantle contribution and comparison with KamLAND data.

Findings

Detected 14.3 geo-neutrino events with 6×10^{-6} null probability.

Measured geo-neutrino signal of 38.8 TNU with uncertainties.

Reactor anti-neutrino signal consistent with expectations.

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 $\pm$ 0.16) $\times$ $10^{31}$ proton $\times$ year after all selection cuts and background subtraction, we detected (14.3 $\pm$ 4.4) geo-neutrino events assuming a fixed chondritic mass Th/U ratio of 3.9. This corresponds to a geo-neutrino signal $S_{geo}$ = (38.8 $\pm$ 12.0) TNU with just a 6 $\times$ $10^{-6}$ probability for a null geo-neutrino measurement. With U and Th left as free parameters in the fit, the relative signals are $S_{\mathrm{Th}}$ = (10.6 $\pm$ 12.7) TNU and $S_\mathrm{U}$ = (26.5 $\pm$ 19.5) TNU. Borexino data alone are compatible with a mantle geo--neutrino signal of (15.4 $\pm$ 12.3) TNU, while a combined analysis with the KamLAND data allows to extract a mantle signal of (14.1 $\pm$ 8.1) TNU. Our measurement of a reactor anti--neutrino signal $S_{react}$ = 84.5$^{+19.3}_{-18.9}$ TNU is in agreement with expectations in the presence of neutrino oscillations.