KamLAND-Zen中\(^{136}Xe\)双中微子ββ能谱的精确分析及其对核矩阵元猝灭的影响。
Precision Analysis of the ^{136}Xe Two-Neutrino ββ Spectrum in KamLAND-Zen and Its Impact on the Quenching of Nuclear Matrix Elements.
作者信息
Gando A, Gando Y, Hachiya T, Ha Minh M, Hayashida S, Honda Y, Hosokawa K, Ikeda H, Inoue K, Ishidoshiro K, Kamei Y, Kamizawa K, Kinoshita T, Koga M, Matsuda S, Mitsui T, Nakamura K, Ono A, Ota N, Otsuka S, Ozaki H, Shibukawa Y, Shimizu I, Shirahata Y, Shirai J, Sato T, Soma K, Suzuki A, Takeuchi A, Tamae K, Ueshima K, Watanabe H, Chernyak D, Kozlov A, Obara S, Yoshida S, Takemoto Y, Umehara S, Fushimi K, Hirata S, Berger B E, Fujikawa B K, Learned J G, Maricic J, Winslow L A, Efremenko Y, Karwowski H J, Markoff D M, Tornow W, O'Donnell T, Detwiler J A, Enomoto S, Decowski M P, Menéndez J, Dvornický R, Šimkovic F
机构信息
Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan.
Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan.
出版信息
Phys Rev Lett. 2019 May 17;122(19):192501. doi: 10.1103/PhysRevLett.122.192501.
We present a precision analysis of the ^{136}Xe two-neutrino ββ electron spectrum above 0.8 MeV, based on high-statistics data obtained with the KamLAND-Zen experiment. An improved formalism for the two-neutrino ββ rate allows us to measure the ratio of the leading and subleading 2νββ nuclear matrix elements (NMEs), ξ_{31}^{2ν}=-0.26_{-0.25}^{+0.31}. Theoretical predictions from the nuclear shell model and the majority of the quasiparticle random-phase approximation (QRPA) calculations are consistent with the experimental limit. However, part of the ξ_{31}^{2ν} range allowed by the QRPA is excluded by the present measurement at the 90% confidence level. Our analysis reveals that predicted ξ_{31}^{2ν} values are sensitive to the quenching of NMEs and the competing contributions from low- and high-energy states in the intermediate nucleus. Because these aspects are also at play in neutrinoless ββ decay, ξ_{31}^{2ν} provides new insights toward reliable neutrinoless ββ NMEs.
基于KamLAND-Zen实验获得的高统计量数据，我们对能量高于0.8兆电子伏特的(^{136}Xe)双中微子(\beta\beta)电子能谱进行了精确分析。一种改进的双中微子(\beta\beta)衰变率形式体系使我们能够测量主导和次主导的双中微子(\beta\beta)核矩阵元（NMEs）的比值，(\xi_{31}^{2\nu}=-0.26_{-0.25}^{+0.31})。核壳模型的理论预测以及大多数准粒子随机相位近似（QRPA）计算结果与实验限值一致。然而，QRPA所允许的(\xi_{31}^{2\nu})范围的一部分在90%置信水平下被当前测量排除。我们的分析表明，预测的(\xi_{31}^{2\nu})值对NMEs的猝灭以及中间核中低能态和高能态的竞争贡献敏感。由于这些方面在无中微子(\beta\beta)衰变中也起作用，(\xi_{31}^{2\nu})为可靠的无中微子(\beta\beta) NMEs提供了新的见解。
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