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Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun

Agostini, M ; Altenmüller, K ; Appel, S ; Atroshchenko, V ; Bagdasarian, Z ; Basilico, D ; Bellini, G

Nature (London), 2020-11, Vol.587 (7835), p.577-582 [Periódico revisado por pares]

England: Nature Publishing Group

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  • Título:
    Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun
  • Autor: Agostini, M ; Altenmüller, K ; Appel, S ; Atroshchenko, V ; Bagdasarian, Z ; Basilico, D ; Bellini, G
  • Assuntos: Astrophysics ; Bismuth ; Bismuth isotopes ; Carbon ; Carbon cycle ; Chains ; Energy ; Experiments ; Helium ; High Energy Physics - Experiment ; Hydrogen ; Instrumentation and Detectors ; Massive stars ; Metallicity ; Neutrinos ; Nitrogen ; Observations ; Origin ; Oxygen ; Physics ; Scintillation counters ; Sensors ; Solar core ; Solar energy ; Solar physics ; Spectrum analysis ; Sun
  • É parte de: Nature (London), 2020-11, Vol.587 (7835), p.577-582
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
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  • Descrição: For most of their existence, stars are fuelled by the fusion of hydrogen into helium. Fusion proceeds via two processes that are well understood theoretically: the proton-proton (pp) chain and the carbon-nitrogen-oxygen (CNO) cycle . Neutrinos that are emitted along such fusion processes in the solar core are the only direct probe of the deep interior of the Sun. A complete spectroscopic study of neutrinos from the pp chain, which produces about 99 per cent of the solar energy, has been performed previously ; however, there has been no reported experimental evidence of the CNO cycle. Here we report the direct observation, with a high statistical significance, of neutrinos produced in the CNO cycle in the Sun. This experimental evidence was obtained using the highly radiopure, large-volume, liquid-scintillator detector of Borexino, an experiment located at the underground Laboratori Nazionali del Gran Sasso in Italy. The main experimental challenge was to identify the excess signal-only a few counts per day above the background per 100 tonnes of target-that is attributed to interactions of the CNO neutrinos. Advances in the thermal stabilization of the detector over the last five years enabled us to develop a method to constrain the rate of bismuth-210 contaminating the scintillator. In the CNO cycle, the fusion of hydrogen is catalysed by carbon, nitrogen and oxygen, and so its rate-as well as the flux of emitted CNO neutrinos-depends directly on the abundance of these elements in the solar core. This result therefore paves the way towards a direct measurement of the solar metallicity using CNO neutrinos. Our findings quantify the relative contribution of CNO fusion in the Sun to be of the order of 1 per cent; however, in massive stars, this is the dominant process of energy production. This work provides experimental evidence of the primary mechanism for the stellar conversion of hydrogen into helium in the Universe.
  • Editor: England: Nature Publishing Group
  • Idioma: Inglês
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