Geoneutrinos and the Earth inner parts structure

The connection between geoneutrino registration and the Earth theory test is discussed. We compare standard theory of lithosphere plates and hypothesis of hydride Earth. Last hypothesis adds additional neutrino source $-$ planet core in which the initial Earth composition is conserved. Large volume scintillation detector is supposed to install at Baksan neutrino observatory INR RAS at Caucasus. The detector will register all possible neutrino fluxes, but mainly geo-neutrinos. So kind a detector (or detector net) placed in a number of sites on the Earth surface can measure all radioactivity from $^{238}$U and $^{232}$Th, because their neutrino energy exceeds the inverse beta-decay reaction threshold. By this way it will it possible to understand if there are any more neutrino sources in the Earth other than the crust and mantle.

💡 Research Summary

The paper proposes a comprehensive program to use geoneutrino detection as a direct probe of the Earth’s interior composition and to test competing models of Earth structure. It begins by reviewing the conventional plate‑tectonic view, which attributes most of the Earth’s internal heat to the radioactive decay of ^238U, ^232Th, and ^40K concentrated in the crust and mantle. In contrast, the “Hydride Earth” hypothesis posits that a substantial fraction of the planet’s primordial material, possibly in the form of metal‑hydride phases, is retained in the core and that this core could act as an additional source of antineutrinos. If true, the core would contribute a measurable flux of antineutrinos beyond that expected from the crust and mantle alone.

To test these ideas, the authors outline the design of a large‑volume liquid‑scintillator detector (LSD) to be installed at the Baksan Neutrino Observatory in the Caucasus. The detector, on the order of ten kilotons of organic scintillator, will exploit the inverse beta‑decay reaction (ν̄_e + p → e⁺ + n) with a threshold of 1.8 MeV, which is comfortably below the energies of antineutrinos emitted in the ^238U and ^232Th decay chains. The design emphasizes high light yield, ~5 % energy resolution at 1 MeV, and excellent timing to separate the prompt positron signal from the delayed neutron capture. Background suppression strategies include deep underground placement (~1 km rock overburden), extensive passive shielding (lead, concrete), and active veto systems to reject cosmic‑muon induced events.

A key innovation is the proposal of a global network of similar detectors placed at several geographically diverse sites (continental crust, oceanic crust, and possibly deep‑sea locations). By comparing the measured antineutrino fluxes at each site, the contributions from the crust, mantle, and core can be disentangled statistically. The authors argue that crust‑dominated sites will primarily measure the local ^238U/^232Th abundance, whereas oceanic sites, with thinner crust, will be more sensitive to mantle contributions. Any excess flux common to all sites, after accounting for crust and mantle models, could be attributed to a core source.

The expected scientific outcomes are twofold. First, the experiment will provide a high‑precision, model‑independent estimate of the total radiogenic heat production of the Earth, refining the current estimate that radioactive decay supplies roughly 20 % of the total heat flow. Second, detection of a core‑origin antineutrino component would constitute direct evidence for the Hydride Earth hypothesis, with profound implications for our understanding of core composition, the long‑term stability of the geomagnetic field, and the processes that governed planetary differentiation.

The paper also discusses future upgrades: adoption of newer scintillating solvents (e.g., linear alkylbenzene), higher‑quantum‑efficiency photomultiplier tubes, and advanced data‑analysis techniques such as machine‑learning‑based background discrimination. Moreover, the authors envision simultaneous studies of solar, supernova, and reactor antineutrinos, turning the detector network into a multi‑purpose observatory for both geophysics and particle physics. In summary, the proposed geoneutrino program offers a novel, direct window into the deep Earth, promises to resolve long‑standing debates about the planet’s heat budget, and could potentially reveal a previously hidden source of antineutrinos residing in the Earth’s core.