Expected geoneutrino signal at JUNO

Abstract

Constraints on the Earth's composition and on its radiogenic energy budget come from the detection of geoneutrinos. The Kamioka Liquid scintillator Antineutrino Detector (KamLAND) and Borexino experiments recently reported the geoneutrino flux, which reflects the amount and distribution of U and Th inside the Earth. The Jiangmen Underground Neutrino Observatory (JUNO) neutrino experiment, designed as a 20 kton liquid scintillator detector, will be built in an underground laboratory in South China about 53 km from the Yangjiang and Taishan nuclear power plants, each one having a planned thermal power of approximately 18 GW. Given the large detector mass and the intense reactor antineutrino flux, JUNO aims not only to collect high statistics antineutrino signals from reactors but also to address the challenge of discriminating the geoneutrino signal from the reactor background. The predicted geoneutrino signal at JUNO is 39:7 þ6:5 −5:2 terrestrial neutrino unit (TNU), based on the existing reference Earth model, with the dominant source of uncertainty coming from the modeling of the compositional variability in the local upper crust that surrounds (out to approximately 500 km) the detector. A special focus is dedicated to the 6°× 4°local crust surrounding the detector which is estimated to contribute for the 44% of the signal. On the basis of a worldwide reference model for reactor antineutrinos, the ratio between reactor antineutrino and geoneutrino signals in the geoneutrino energy window is estimated to be 0.7 considering reactors operating in year 2013 and reaches a value of 8.9 by adding the contribution of the future nuclear power plants. In order to extract useful information about the mantle's composition, a refinement of the abundance and distribution of U and Th in the local crust is required, with particular attention to the geochemical characterization of the accessible upper crust where 47% of the expected geoneutrino signal originates and this region contributes the major source of uncertainty.

Neutrinos from the Earth: Status and Perspectives

“…As reported in [12] in year 2020 the ratio will increase of about one order of magnitude. But nevertheless due to the huge mass ( 20 kt), the collection of a high statistic could provide interesting results on geoneutrinos, in particular during the temporary switching off for ordinary plants maintenance, see [16].…”

Potential of geo-neutrino measurements at JUNO

“…[10], an accuracy of 18% is estimated for the crust geo-neutrino contribution using the global reference Earth model in Ref. [11].…”

“…(7) by using the pull method, where the prediction in Eq. (7) is defined as (10) where N pred i,geo will be specified in the following for different fitting scenarios.…”

“…where S L (U) = 23.2 +5.9 −4.8 TNU [10] is the signal from lithosphere and β defines the signal contribution from the mantle. We assume two limiting cases for the value of β in a spherically symmetric mantle:…”

“…[10], where they adopted the reference Earth model (RM) developed by Huang et al [11]. The RM model divides the silicate Earth into eight lithospheric reservoirs (ice, water, soft and hard sediment, upper, middle and lower continental crust, and lithospheric mantle) and two mantle reservoirs (depleted and enriched).…”