Measurement of geo-neutrinos from 1353 days of Borexino

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) 10 31 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 S geo = (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 S Th = (10.6 12.7) TNU and S U = (26.5 19.5) TNU. Borexino data alone are compatible with a mantle geo-neutrino signal of