Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun-猫眼课题宝

DOI：

10.1038/s41586-020-2934-0

发表时间：

2020-06

期刊：

Nature

影响因子：

64.8

通讯作者：

中科院分区：

综合性期刊1区

文献类型：

作者：

M. K. S. V. Z. D. G. J. R. D. B. F. A. P. A. D. S. A. Agostini Altenmüller Appel Atroshchenko Bagdasaria-M.-K.-S.-V.-Z.-D.-G.-J.-R.-D.-B.-F.-A.-P.-A.-D.-S.;M. Agostini;K. Altenmüller;S. Appel;V. Atroshchenko;Z. Bagdasarian;D. Basilico;G. Bellini;J. Benziger;R. Biondi;D. Bravo;B. Caccianiga;F. Calaprice;A. Caminata;P. Cavalcante;A. Chepurnov;D. D’Angelo;S. Davini;A. Derbin;A. Di Giacinto;V. Di Marcello;X. Ding;A. Di Ludovico;L. Di noto;I. Drachnev;A. Formozov;D. Franco;C. Galbiati;C. Ghiano;M. Giammarchi;A. Goretti;A. Göttel;M. Gromov;D. Guffanti;A. Ianni;A. Ianni;A. Jany;D. Jeschke;V. Kobychev;G. Korga;S. Kumaran;M. Laubenstein;E. Litvinovich;P. Lombardi;I. Lomskaya;L. Ludhova;G. Lukyanchenko;L. Lukyanchenko;I. Machulin;J. Martyn;E. Meroni;M. Meyer;L. Miramonti;M. Misiaszek;V. Muratova;B. Neumair;M. Nieslony;R. Nugmanov;L. Oberauer;V. Orekhov;F. Ortica;M. Pallavicini;L. Papp;L. Pelicci;Ö. Penek;L. Pietrofaccia;N. Pilipenko;A. Pocar;G. Raikov;M. Ranalli;G. Ranucci;A. Razeto;A. Re;M. Redchuk;A. Romani;N. Rossi;S. Schönert;D. Semenov;G. Settanta;M. Skorokhvatov;A. Singhal;O. Smirnov;A. Sotnikov;Y. Suvorov;R. Tartaglia;G. Testera;J. Thurn;E. Unzhakov;F. Villante;A. Vishneva;R. Vogelaar;F. von Feilitzsch;M. Wójcik;M. Wurm;S. Zavatarelli;K. Zuber;G. Zuzel

在它们存在的大部分时间里，恒星的燃料来自氢与氦的聚变。核聚变通过两个理论上很好理解的过程进行：质子-质子（pp）链和碳-氮-氧（CNO）循环。在太阳核心的这种聚变过程中释放出的中微子是对太阳内部深处的唯一直接探测。以前已经对来自ppchain的中微子进行了完整的光谱研究，ppchain产生了大约99%的太阳能；然而，目前还没有关于CNO循环的实验证据。在这里，我们报告了对太阳CNO循环中产生的中微子的直接观测，具有很高的统计意义。这一实验证据是利用位于意大利Gran Sasso地下实验室的Borexino的高放射性、大体积液体闪烁探测器获得的。主要的实验挑战是确定多余的信号——每100吨目标中每天只有几次高于背景的信号——这归因于CNO中微子的相互作用。在过去的五年里，探测器热稳定性的进步使我们能够开发出一种方法来限制铋-210污染闪烁体的速率。在CNO循环中，氢的聚变是由碳、氮和氧催化的，所以它的速率——以及发射的CNO中微子的通量——直接取决于太阳核心中这些元素的丰度。因此，这一结果为使用CNO中微子直接测量太阳金属丰度铺平了道路。我们的研究结果量化了太阳中CNO聚变的相对贡献，约为1%；然而，在大质量恒星中，这是能量产生的主要过程。这项工作为宇宙中恒星将氢转化为氦的主要机制提供了实验证据。

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 theppchain, 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.

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

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