A rare mineral is illuminating four million years of solar history

The LOREX experiment uses lorandite ore to measure the historical flux of solar neutrinos, allowing it to reveal new information about the Sun’s development and climate effects.

Our star produces a lot of energy through nuclear fusion while emitting a constant stream of neutrinos, subatomic particles that reveal its inner workings.

Although the detectors help to understand the behavior of the Sun, there are still questions to be resolved, particularly related to its stability over millions of years.

The mission of LORandite EXPERIMENT (LOREX) – whose objective is to determine the average flux of solar neutrinos over an extraordinary period of four million years that corresponds to the geological age of the lorandite ore – is precisely to unravel these still unanswered mysteries through measurement of the solar neutrino cross section for thallium.

Recently, an international team of scientists achieved this long-awaited measurement, using the Experimental Storage Ring (ESR) no GSI/FAIR, em Darmstadt.

Neutrinos produced by the Sun interact with thallium (Tl) atoms found in the mineral lorandite (TlAsS₂), converting them into lead (Pb) atoms.

O isotope ²⁰⁵Pb It is especially significant because of its long half-life of 17 million years, meaning it remains stable over the four million year period of lorandite ore.

How to directly measure the interaction cross section of neutrinos with ²⁰⁵Tl is not viable, scientists created an innovative approach: they focused on a fundamental property of nuclear physics, known as nuclear matrix elementwhich influences both the neutrino interaction rate and the beta decay of the bound state of ²⁰ Tl⁸¹⁺ fully ionized to 205 Pb⁸¹⁺ .

This method allowed the team to extract essential data needed to calculate neutrino cross section.

According to , the experimental measurement of the half-life of the beta decay of the bound state of ions ²⁰⁵Tl⁸¹⁺ fully ionized was only possible thanks to the unique capabilities of Experimental Storage Ring (ESR).

The ESR is currently the only facility where these types of measurements are feasible. The ions ²⁰⁵Tl⁸¹⁺ were produced using nuclear reactions in the Fragment Separator (FRS) of GSI/FAIR and stored long enough for its decay to be successfully observed and measured in the storage ring.

“The team measured the beta decay half-life of ²⁰⁵Tl⁸¹⁺ in 291 (+33/-27) daysan essential measurement that allows us to determine the solar neutrino capture cross-section,” explained Rui-Jiu Chen, a researcher involved in the project.

As soon as the concentration of carbon atoms ²⁰⁵Pb in lorandite minerals is determined by the LOREX project, it will be possible to provide new information on the evolutionary history of the Sun and its relationship with the Earth’s climate over the millennia.

The was published in Physical Review Letters.