For the first time, physicists have detected rare, ghost particles produced by a strange fusion in the sun.
Particles called neutrinos produced by CNO (carbon-nitrogen-oxygen) went from the sun to a detector buried deep within a mountain in Italy. This discovery takes people one step closer to understanding the fiery nuclear reactions that nourish our star.
Physicist Gioacchino Ranucci, a physicist from Italy's National Institute of Nuclear Physics, in an interview with Live Science; "With this result, Borexino completely resolved two processes that power the sun."
Two types of nuclear fusion reactions occur in the sun's core. The first and most common is proton-proton fusion, in which protons combine to convert hydrogen into helium. Scientists estimate that such reactions produce 99% of solar energy. Rarely, nuclear fusion occurs through a six-stage process called the CNO cycle, in which hydrogen is fused into helium using carbon (c), nitrogen (N), and oxygen (O). Proton-proton fusion and the CNO cycle form different types of neutrinos, subatomic particles that are nearly massless and can pass through ordinary matter, at least often without a clue as to their existence. Physicists routinely detect neutrinos created during the proton-proton process. However, on June 23, at the neutrino 2020 virtual meeting, researchers from Italy's Borexino detector announced that they had detected solar neutrinos produced by CNO for the first time.
The underground Borexino experiment at Laboratori Nazionali
del Gran Sasso, near the town of L'aquila, Italy, was designed to study these
extremely rare neutrino interactions. The Borexino detector consists of a tank
about 60 feet (18 meters) high, containing 280 tons (254 metric tons) of
scintillation fluid - which flashes when electrons in the liquid interact with
a neutrino. A bright flash showing higher energy is more likely to be from
neutrinos produced by the CNO.
Buried deep underground and cocooned in a water tank, Borexino's inner tank is covered with sensitive detectors that are highly isolated from background radiation from cosmic rays found on the Earth's surface. Without this protection, other signals overwhelm rare signals from CNO neutrinos.
Ranucci also transfers the experiment to the "unprecedented purity" of the scintillation fluid with much of the success.
Comparing the observed CNO neutrino observation with the number of observed proton-proton neutrinos will help to reveal how much of the sun is made up of elements heavier than hydrogen, such as carbon, nitrogen and oxygen. The current results, though not yet scientifically published and published in a scientific journal, showed greater significance than 5 sigma with a confidence level of more than 99%, meaning the probability of random generation of the signal fluctuates rather than just 1 CNO process in 3.5 million.
The Borexino international collaboration consists of researchers from Italy, France, Germany, Poland, Russia, and three universities from the United States, Princeton, Virginia Tech, and the University of Massachusetts at Amherst.