GUESS - GeoneUtrinos: mESSengers of the Earth's interior

Abstract:

Geoneutrinos, antineutrinos from the decays of natural radionuclides in the Earth, can escape freely from Earth’s interior bringing to surface information from the whole planet. Since U and Th release heat and antineutrinos in fixed ratios, an antineutrino flux measures provides a direct information on the amount of radioactive material inside Earth and thus of its radiogenic heat. Moreover, given an accurate prediction of the geoneutrino signal produced by U and Th distribution in the accessible lithosphere, the mantle signal can be derived.
GUESS aims at providing a new reference estimate of the local crustal geoneutrino signal at the Borexino (BX) experiment, a low-energy neutrino detector operative in Italy since 2007. The actual reference model of the Th and U abundances and distribution surrounding the BX detector (closest 500 km, which typically contributes 40-50% of the measured signal) predicts a low contribution to the overall geoneutrino signal. Consequently, the inferred mantle geoneutrino signal is high (S_M = 21 TNU), as well as the calculated Earth’s radiogenic power (H = 38 TW). This prediction contrasts with the result of the KamLAND experiment (S_M = 5 TNU, H = 15 TW), the only operational experiment measuring so far geoneutrinos beside BX. It is evident as a reliable interpretation of the regional geology is crucial since it influences the mantle signal and its uncertainty and in turn the inferred U and Th global abundances and the radiogenic power. GUESS will impressively enhance the potentialities of BX measurements for unveiling the deep Earth, realizing an up to date and refined 3D model of the crust surrounding the detector.
The expected outcomes will impact BX analysis and future multi-sites studies from on-going and upcoming experiments. GUESS proposes an innovative and interdisciplinary approach focused on the construction of a 3D geophysical and geochemical model, providing an advancement of knowledge at the level of the single disciplines and in view of defining a new reference methodology to be adopted by the neutrino geoscience community.
The achievement of the targets will be possible thanks to the consolidated cooperation among the RUs in other research projects as well as the highly qualified and complementary expertise in gamma-ray and antineutrino spectroscopy (UNIFE), in satellite and ground gravimetric data inversion (POLIMI) and in the understanding of the geology of Central Italy (UNISI).
The development of original and trans-disciplinary expertise will lead to the consolidation of the researchers leading the project and to the formation of top-level young researchers. As a byproduct, GUESS will stimulate the transmission of know-how and expertise to innovative technological realities. As demonstrated by the endorsement letters, GUESS will have a practical impact on society and industrial applications in various sectors, also addressing strategic questions from basic science.