arXiv 1003.02842010-03-20hep-ex

地球中微子的观测

Observation of Geo-Neutrinos

Borexino Collaboration

备注：: 8 pages, 4 figures, 3 tables
发表信息：: Phys.Lett.B687:299-304,2010
DOI：: 10.1016/j.physletb.2010.03.051

摘要：

地球中微子是地球中天然放射性同位素的β衰变产生的电子反中微子，是对地球内部的独特直接探测。我们报告的第一个观察超过3 $σ$ C. L。在Gran Sasso国家实验室的Borexino探测器上进行。反中微子是通过中子逆β衰变反应探测到的。在252.6吨/年的基准曝光量下，我们探测到了9.9^{+4.1}_{-3.4}（^{+14.6}_{-8.2}）个地中微子事件，对应于68.3%（99.73%）的C.根据$\ln{\cal{L}}$剖面，Borexino地中微子观测的统计显著性对应于99.997% C. L.。我们测得地球中微子的速率为3.9^{+1.6}_{-1.3}（^{+5.8}_{-3.2}）个事件/（100吨-年）。这一测量结果否定了地球核心中有一个活跃的地质反应堆的假设，该反应堆在95% C. L.时的功率超过3 TW。所观察到的2.6兆电子伏以上的提示正电子谱是兼容的预期从欧洲核反应堆（平均基线约1000公里）。我们对反应堆反中微子的测量排除了99.60%C. L.的非振荡假设。

英文摘要：

Geo-neutrinos, electron anti-neutrinos produced in beta decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. We report the first observation at more than 3$σ$ C.L. of geo-neutrinos, performed with the Borexino detector at Laboratori Nazionali del Gran Sasso. Anti-neutrinos are detected through the neutron inverse beta decay reaction. With a 252.6 ton-yr fiducial exposure after all selection cuts, we detected 9.9^{+4.1}_{-3.4}(^{+14.6}_{-8.2}) geo-neutrino events, with errors corresponding to a 68.3%(99.73%) C.L. From the $\ln{\cal{L}}$ profile, the statistical significance of the Borexino geo-neutrino observation corresponds to a 99.997% C.L. Our measurement of the geo-neutrinos rate is 3.9^{+1.6}_{-1.3}(^{+5.8}_{-3.2}) events/(100ton-yr). This measurement rejects the hypothesis of an active geo-reactor in the Earth's core with a power above 3 TW at 95% C.L. The observed prompt positron spectrum above 2.6 MeV is compatible with that expected from european nuclear reactors (mean base line of approximately 1000 km). Our measurement of reactor anti-neutrinos excludes the non-oscillation hypothesis at 99.60% C.L.

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英文摘要：

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