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Neutrinos are uncharged particles with a mass about one millionth of that of an electron that are created by the nuclear processes that take place in the Sun and other stars. These particles are often colorfully described as the “ghosts” of the particle zoo because they interact so weakly with matter. An article published in EPJ C from the Borexino collaboration – which includes XueFeng Ding, Postdoc Associate of Physics at Princeton University, USA – documents for the first time the attempts of the Borexino experiment to measure low-energy neutrinos from the solar carbon-nitrogen-oxygen (CNO) cycle.
“This gigantic instrument, buried beneath the Gran Sasso mountains in Italy’s Gran Sasso National Laboratory, is capturing ghost-like neutrinos from a so-called CNO process in the center of the sun,” explains Ding. “We did tens of thousands of simulations and predicted that we would be able to prove that these” CNO “ghosts exist for the first time in human history.”
The Sun produces energy by converting four hydrogen nuclei into a helium nucleus through two mechanisms. Most of the energy produced by the Sun is initiated by the direct fusion of two protons in a deuteron, starting the pp chain, the other mechanism is catalyzed by heavier nuclei, such as carbon, nitrogen and oxygen, known as the CNO cycle – which produces about 1% of our star’s energy output. In addition to this small energy contribution, the CNO cycle is also expected to produce about 1% of the neutrinos that flow from the Sun.
“The neutrinos of the CNO cycle process in the Sun remained essentially hypothetical until Borexino’s recent report on the Neutrino 2020 conference,” says Ding. “Borexino has been searching for CNO neutrinos since 2016 after the installation of the thermal insulation system and the active temperature control system. This paper reports a quantitative study on the sensitivity of Borexino in the search for CNO neutrinos and explains the methodology”.
Since the Sun itself has only a 1% CNO branch and since neutrinos are already incredibly difficult to detect, there has not yet been any measurement of the CNO process itself, even though it is believed to be the main pathway of energy production. in the stars. more massive than the sun. Detecting neutrinos from the CNO cycle will teach researchers a lot more about it, in turn revealing the secrets locked beneath the surface of the most massive stars in the Universe.
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References
M. Agostini et al. (Collaboration BOREXINO), (2020), Sensitivity to neutrinos from the solar CNO cycle at Borexino, European Physical Journal C 80: 1091, DOI 10.1140 / epjc / s10052-020-08534-2
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