First measurement of low-energy solar neutrinos scattering off electrons
Every second, tens of billions of neutrinos produced by nuclear fusion in the sun pass through every square centimeter of Earth—and through our bodies—almost without interacting. Although they are among the most abundant particles emitted by the sun, their extremely weak interactions make detecting these elusive particles one of the greatest experimental challenges in particle physics. A number…
Researchers in the XENON Collaboration revealed the first detection of low-energy solar neutrinos interacting with electrons in the XENONnT detector, according to a presentation held on August 31 at a seminar hosted by the INFN Laboratori Nazionali del Gran Sasso in Italy. This groundbreaking discovery, available on the arXiv preprint server, pushes the limits of direct neutrino observations down to neutrino energies of approximately 17 keV, marking the lowest neutrino energy threshold ever achieved.
The detected signal is primarily attributed to pp neutrinos, which are generated through proton-proton fusion reactions powering the sun and contributing to the majority of its neutrino emissions. The INFN National Laboratory of Frascati, located 1,400 meters beneath the Gran Sasso massif, houses the detector, a dual-phase xenon time projection chamber filled with 5.9 metric tons of highly pure liquid xenon.
The international research effort, involving about 30 facilities, includes the University of Zurich. Although originally designed for the search for particle dark matter, this new measurement demonstrates that the same detector can also probe complementary aspects of neutrino physics. This development highlights the detector's sensitivity to extremely low-energy neutrinos produced in the sun and positions XENONnT as one of the world's most sensitive observatories for rare low-energy particle interactions.
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