Oscillation tomografy study of Earth’s composition and density with atmospheric neutrinos

Abstract

Knowledge of the composition of the Earth’s interior is highly relevant to many geophysical and geochemical problems. Neutrino oscillations are modified in a non-trivial way by the matter effects and can provide valuable and unique information not only on the density but also on the chemical and isotopic composition of the deep regions of the planet. In this paper, we re-examine the possibility of performing an oscillation tomography of the Earth with atmospheric neutrinos and antineutrinos to obtain information on the composition and density of the outer core and the mantle, complementary to that obtained by geophysical methods. Particular attention is paid to the D$$^{\prime \prime }$$ ″ layer just above the core-mantle boundary and to the water (hydrogen) content in the mantle transition zone. Our analysis is based on a Monte-Carlo simulation of the energy and azimuthal angle distribution of $$\mu $$ μ -like events generated by neutrinos. Taking as reference a model of the Earth consisting of 55 concentric layers with constant densities determined from the PREM, we evaluate the effect on the number of events due to changes in the composition and density of the outer core and the mantle. To examine the capacity of a detector like ORCA to resolve such variations, we construct regions in planes of two of these quantities where the statistical significance of the discrepancies between the reference and the modified Earth are less than $$1\sigma $$ 1 σ . The variations are implemented in such a way that the constraint imposed by both the total mass of the Earth and its moment of inertia are verified.

Locating the core-mantle boundary using oscillations of atmospheric neutrinos

“…The possibility of probing the internal structure of Earth using these density-dependent matter effects is known as "neutrino oscillation tomography". These studies have been performed using man-made neutrino beams [61][62][63][64][65][66][67][68][69][70][71], supernova neutrinos [72,73], solar neutrinos [72,[74][75][76][77][78][79], and atmospheric neutrinos [80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95]. In the sub-GeV and multi-GeV energy ranges, atmospheric neutrinos are the best source of neutrinos to probe the internal structure of Earth because they have access to a wide range of baselines starting from about 15 km to 12750 km which cover all the layers of Earth.…”

“…Sensitivity studies for the current and future atmospheric neutrino experiments like IceCube [82], Precision IceCube Next Generation Upgrade (PINGU) [81], Oscillation Research with Cosmics in the Abyss (ORCA) [96], Deep Underground Neutrino Experiment (DUNE) [97], Hyper-Kamiokande (Hyper-K) [98], and Iron Calorimeter (ICAL) detector [88] have been performed. These studies have shown how to detect the presence of core-mantle boundary using ICAL [88], constrain the average densities of the core, and the mantle using ORCA [83,90,91,95] and DUNE [89], determine the position of the core-mantle boundary using DUNE [92], and explore the chemical composition of the Earth's core using PINGU [81], Hyper-K and IceCube [82], as well as ORCA [84-86, 90, 94, 95].…”