Speaker
Description
The Jiangmen Underground Neutrino Observatory (JUNO) in China, successfully started taking physics data in August 2025, following a 15-year journey from design to completion. Designed to determine the neutrino mass ordering, JUNO is located 52.5 km from eight nuclear reactors, making reactor antineutrinos the dominant signal source. Nonetheless, thanks to its large size of 20 kton of liquid scintillator, it is also expected to detect more than 400 geoneutrinos per year. These are electron antineutrinos that originate from the decay of long-lived radioactive elements within the Earth. Due to the inverse beta decay detection threshold, JUNO is only sensitive to geoneutrinos from the Uranium-238 and Thorium-232 decay chains.
The relation between the geoneutrino flux and heat released in these decays is well established. Thus the measurement of the flux can provide insights into the Earth’s energy budget and, consequently, into Earth’s dynamics and formation. More than 50% of the signal is expected to come from the local lithosphere, within a few hundred kilometers around the detector. Bulk Silicate Earth (BSE) models aim to describe the composition of the primitive silicate Earth, from which the present-day mantle and crust were formed through differentiation. The lithospheric contribution can be constrained more directly thanks to in-situ and geological measurements, whereas the mantle component is typically inferred indirectly by subtracting the modeled lithosphere from the BSE prediction. The total predicted geoneutrino signal is therefore the sum of the lithospheric and mantle contributions, and depends on the assumed BSE model.
This poster presents JUNO’s first geoneutrino measurement, and compares it to the predicted signal from existing geological models.