Spectroscopy of geo-neutrinos from 2056 days of Borexino data

TL;DR

This paper reports an improved measurement of geo-neutrinos using 2056 days of Borexino data, providing insights into Earth's radiogenic heat and mantle composition with high statistical significance.

Contribution

The study presents the most precise geo-neutrino measurement from Borexino to date, including a significant detection of mantle geo-neutrinos and constraints on Earth's radiogenic heat production.

Findings

Detection of 23.7 geo-neutrino events with high significance

Evidence for mantle geo-neutrino signal at 98",

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Abstract

We report an improved geo-neutrino measurement with Borexino from 2056 days of data taking. The present exposure is $(5.5\pm0.3)\times10^{31}$ proton$\times$yr. Assuming a chondritic Th/U mass ratio of 3.9, we obtain $23.7 ^{+6.5}_{-5.7} (stat) ^{+0.9}_{-0.6} (sys)$ geo-neutrino events. The null observation of geo-neutrinos with Borexino alone has a probability of $3.6 \times 10^{-9}$ (5.9$\sigma$). A geo-neutrino signal from the mantle is obtained at 98\% C.L. The radiogenic heat production for U and Th from the present best-fit result is restricted to the range 23-36 TW, taking into account the uncertainty on the distribution of heat producing elements inside the Earth.