ausblenden:
Schlagwörter:
High Energy Physics - Experiment, hep-ex, Physics, Instrumentation and Detectors, physics.ins-det
Zusammenfassung:
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.
