Combined analysis of KamLAND and Borexino neutrino signals from Th and U decays in the Earth's interior

Understand

The KamLAND and Borexino experiments have detected electron antineutrinos produced in the decay chains of natural thorium and uranium (Th and U geoneutrinos).

• We analyze the energy spectra of current geoneutrino data in combination with solar and long-baseline reactor neutrino data, with marginalized three-neutrino oscillation parameters.
• We consider the case with unconstrained Th and U event rates in KamLAND and Borexino, as well as cases with fewer degrees of freedom, as obtained by successively assuming for both experiments a common Th/U ratio, a common scaling of Th+U event rates, and a chondritic Th/U value.
• In combination, KamLAND and Borexino can reject the null hypothesis (no geoneutrino signal) at 5 sigma.