Scientists confirm first observation of solar neutrinos by dark matter detector
This historic result was obtained using XENONnT, a system that detects dark matter with unprecedented sensitivity.
A team of researchers from the Faculty of Sciences of the University of Coimbra - Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys - FCTUC), participating in the international XENON experiment, has for the first time recorded neutrinos from the Sun using coherent elastic neutrino-nucleus scattering (CEvNS).
This historic result was obtained using XENONnT, a system designed to detect dark matter with unprecedented sensitivity, and has been published in the prestigious journal Physical Review Letters.
XENONnT, a system designed to detect dark matt is located deep underground at the INFN Laboratori Nazionali del Gran Sasso (LNGS) in Italy, in a unique environment that significantly reduces cosmic radiation. The results announced are the outcome of data analysis collected over two years, between July 2021 and August 2023.
This system uses six tonnes of ultra-pure liquid xenon as an active target, "When radiation passes through a target, it usually produces tiny light or charge signals. The vast majority of these signals are due to radiation from known sources, allowing scientists to calculate the number of expected events with great precision," says José Matias-Lopes, a researcher at FCTUC's LIBPhys 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 background radiation levels so that you can distinguish what you want to measure. Achieving such a technically challenging goal involves all kinds of radiation sources, those present in the Xenon target itself and those from the materials from which XENONnT is made. To tackle the most difficult of all, the first, the XENON collaboration has succeeded in reducing radon contamination to unprecedented levels.
Neutrinos from the Sun can interact with the nuclei of the xenon atoms in the XENONnT target via coherent elastic neutrino-nucleus scattering (CEvNS). This Standard Model process, first predicted in 1974, has been challenging due to the very low energy recoils and the elusive nature of neutrinos. Only in 2017, the COHERENT experiment reported the first observations of CEvNS with higher energy neutrinos from the Spallation Neutron Source in Oak Ridge, Tennessee (USA).
XENONnT is the first experiment to measure CEvNS from neutrinos produced in the Sun's core and to measure the CEvNS process with the element xenon, joining the list of famous solar neutrino experiments.
"These results herald a new era in the field of dark matter research, making it possible to detect the so-called 'neutrino fog' that exists alongside dark matter. I’m confident that other dark matter detection experiments will confirm these findings, though likely with less statistical significance than the Chinese PandaX-4," José Matias-Lopes concludes
The scientific article “First Indication of Solar 8B Neutrinos via Coherent Elastic Neutrino-Nucleus Scattering with XENONnT” is available here, and the publication in collaboration with PandaX-is available here.