A team of scientists from the University of Coimbra (UC), participating in the international XENON experiment, recorded, for the first time in history, neutrinos coming from inside the Sun with a dark matter detector, the higher education establishment revealed this Wednesday.
The result of the participation of the team of UC scientists – which belongs to the Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys) of the Faculty of Science and Technology of the University of Coimbra (FCTUC) – in the international experience XENON, is published in Physical Review Letters magazine.
It results from the analysis of data acquired over two years, from July 2021 to August 2023.
In a press release sent to the Lusa agency, the University of Coimbra says that “this historic result” was obtained by XENONnT, a system with an unprecedented level of sensitivity in detecting dark matter.
“XENONnT was built for the direct detection of dark matter. It is installed in the underground laboratory of Gran Sasso, in Italy, under 1,300 meters of rock, to drastically reduce the levels of cosmic radiation in relation to those that exist on the surface of our planet”, he informs.
According to UC, this system uses “six tons of ultra-purified xenon” as a target.
“When radiation passes through the target, it can generally generate tiny signals of light and charge. The overwhelming majority of these signals (more than 99.99%) are due to radiation of known origin, which allows scientists to calculate with great precision the number of expected events”, says José Matias-Lopes, researcher at LIBPhys at FCTUC and coordinator of the Portuguese team.
To measure events as rare as neutrinos and dark matter, the most important requirement is that “the target has the lowest possible level of radiation so that it can distinguish what is being measured.”
All types of radiation sources count: “that present in the xenon target itself and that that comes from the materials from which the XENONnT is constructed”.
“To deal with the most difficult of all, the first, the XENON collaboration managed to reduce the level of contamination with the element radon to unprecedented levels thanks to a 5.5 meter high distillation column, specially developed for this purpose by this collaboration”, indicates the researcher.
The target of XENONnT is the place on planet Earth with the lowest background radiation in the entire history of Humanity, allowing it to carry out “studies of a large number of particularly rare phenomena such as the interaction of solar axions, neutrinos with magnetic moment anomalous, of particles analogous to axions, among others”.
“Now, and for the first time, XENONnT is able to measure solar neutrinos by neutrino-nucleus coherent elastic scattering”, he maintains, adding that the ultra-low level of background radiation of this detection system combined with its ability to detect very low energies has allowed this scientific feat.
The measurement was obtained with “2.72 standard deviations of confidence, which means that there is a 99.65% certainty that the recorded signal is from solar neutrinos resulting from nuclear reactions of Boron-8”, making this “the first time that This type of neutrinos is measured from an extraterrestrial source.”
According to José Matias-Lopes, these results begin a new era in the path of dark matter, by starting the detection of the so-called neutrino fog, where these coexist with dark matter, which, as they are almost indistinguishable, makes the detection of this last type of matter difficult. particles.
“Other dark matter detection experiments will certainly also be on the verge of obtaining the same confirmation, as has already happened with the Chinese ‘PandaX-4’, but with less statistical significance”, he concludes.
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