Search for Majorana neutrinos with the first two years of EXO-200 data
Search for Majorana neutrinos with the first two years of EXO-200 data
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DOI：
10.1038/nature13432
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发表时间：
2014-02
期刊：
影响因子：
64.8
通讯作者：
J. B. D. J. P. S. E. D. V. C. J. M. T. A. G. F. C. J. Albert Auty Barbeau Beauchamp Beck Belov Benitez-M-J.-B.-D.-J.-P.-S.-E.-D.-V.-C.-J.-M.-T.-A.-G.-F.-C.;J. Albert;D. Auty;P. Barbeau;E. Beauchamp
中科院分区：
文献类型：
--
作者：
J. B. D. J. P. S. E. D. V. C. J. M. T. A. G. F. C. J. Albert Auty Barbeau Beauchamp Beck Belov Benitez-M-J.-B.-D.-J.-P.-S.-E.-D.-V.-C.-J.-M.-T.-A.-G.-F.-C.;J. Albert;D. Auty;P. Barbeau;E. Beauchamp
粒子物理学标准模型的许多扩展都认为中微子应该是马约拉纳型费米子--也就是说，中微子是它们自己的反粒子--但这个假设很难证实。无中微子双β衰变（0νββ）是一种可能发生在几个候选核中的自发跃迁，它的观测将验证中微子的马约拉纳性质，并限制中微子质谱的绝对标度。最近对76 Ge（GERDA实验）和136 Xe（KamLAND-Zen和EXO（Enriched Xenon Observatory）-200实验）的研究已经确定这种衰变的寿命超过1025年，对应于中微子质量的极限为0.2-0.4电子伏特。在这里，我们报告了EXO-200的新结果，该结果基于大的136 μ m暴露量，比我们早期公布的数据集增加了近四倍。我们改进了探测器的分辨率，并修改了数据分析。我们获得的半衰期灵敏度为1.9 × 1025年，比以前的EXO-200结果提高了2.7倍。我们没有发现0νββ衰变的统计学显著证据，并在90%的置信水平下将半衰期限制为1.1 × 1025年。高灵敏度为EXO-200探测器的进一步运行和未来的0νββ衰变搜索提供了希望，改进了基于Xe的实验nEXO。
Many extensions of the standard model of particle physics suggest that neutrinos should be Majorana-type fermions—that is, that neutrinos are their own anti-particles—but this assumption is difficult to confirm. Observation of neutrinoless double-β decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with76Ge (the GERDA experiment) and136Xe (the KamLAND-Zen and EXO (Enriched Xenon Observatory)-200 experiments) have established the lifetime of this decay to be longer than 1025years, corresponding to a limit on the neutrino mass of 0.2–0.4 electronvolts. Here we report new results from EXO-200 based on a large136Xe exposure that represents an almost fourfold increase from our earlier published data sets. We have improved the detector resolution and revised the data analysis. The half-life sensitivity we obtain is 1.9 × 1025years, an improvement by a factor of 2.7 on previous EXO-200 results. We find no statistically significant evidence for 0νββdecay and set a half-life limit of 1.1 × 1025years at the 90 per cent confidence level. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββdecay searches with an improved Xe-based experiment, nEXO.