Unveiling the outer core composition with neutrino oscillation tomography

Abstract

In the last 70 years, geophysics has established that the Earth’s outer core is an FeNi alloy containing a few percent of light elements, whose nature and amount remain controversial. Besides the classical combinations of silicon and oxygen, hydrogen has been advocated as the only light element that could account alone for both the core density and velocity profiles. Here we show how this question can be addressed from an independent viewpoint, by exploiting the tomographic information provided by atmospheric neutrinos, weakly-interacting particles produced in the atmosphere and constantly traversing the Earth. We evaluate the potential of the upcoming generation of atmospheric neutrino detectors for such a measurement, showing that they could efficiently detect the presence of 1 wt% hydrogen in the Earth’s core in 50 years of concomitant data taking. We then identify the main requirements for a next-generation detector to perform this measurement in a few years timescale, with the further capability to efficiently discriminate between FeNiH and FeNiSixOy core composition models in less than 15 years.