Reactor on-off antineutrino measurement with KamLAND

作者：A. Gando, Y. Gando, H. Hanakago, H. Ikeda, K. Inoue, K. Ishidoshiro, H. Ishikawa, M. Koga, R. Matsuda, Sumio Matsuda, T. Mitsui, D. Motoki, K. Nakamura, A. Obata, A. Oki, Y. Oki, M. Otani, I. Shimizu, J. Shirai, Y. Suzuki, Y. Takemoto, K. Tamae, K. Ueshima, H. Watanabe, B. D. Xu, S. Yamada, Y. Yamauchi, H. P. Yoshida, A. Kozlov, S. Yoshida, A. Piepke, T. Banks, B. K. Fujikawa, K. Han, T. O’Donnell, B. E. Berger, J. G. Learned, S. Matsuno, M. Sakai, Y. Efremenko, H. J. Karwowski, D. M. Markoff, W. Tornow, J. A. Detwiler, S. Enomoto, M. P. Decowski · 发表于：Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 年份：2013 · DOI：10.1103/physrevd.88.033001 · 被引用次数：354 · 研究领域：Neutrino Physics Research、Atomic and Subatomic Physics Research、Astrophysics and Cosmic Phenomena

The recent long-term shutdown of Japanese nuclear reactors has resulted in a significantly reduced reactor ${\overline{\ensuremath{\nu}}}_{e}$ flux at KamLAND. This running condition provides a unique opportunity to confirm and constrain backgrounds for the reactor ${\overline{\ensuremath{\nu}}}_{e}$ oscillation analysis. The data set also has improved sensitivity for other ${\overline{\ensuremath{\nu}}}_{e}$ signals, in particular ${\overline{\ensuremath{\nu}}}_{e}$'s produced in $\ensuremath{\beta}$-decays from $^{238}\mathrm{U}$ and $^{232}\mathrm{Th}$ within the Earth's interior, whose energy spectrum overlaps with that of reactor ${\overline{\ensuremath{\nu}}}_{e}$'s. Including constraints on ${\ensuremath{\theta}}_{13}$ from accelerator and short-baseline reactor neutrino experiments, a combined three-flavor analysis of solar and KamLAND data gives fit values for the oscillation parameters of ${tan}^{2}{\ensuremath{\theta}}_{12}={0.436}_{\ensuremath{-}0.025}^{+0.029}$, $\ensuremath{\Delta}{m}_{21}^{2}={7.53}_{\ensuremath{-}0.18}^{+0.18}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{eV}}^{2}$, and ${sin}^{2}{\ensuremath{\theta}}_{13}={0.023}_{\ensuremath{-}0.002}^{+0.002}$. Assuming a chondritic Th/U mass ratio, we obtain ${116}_{\ensuremath{-}27}^{+28}$ ${\overline{\ensuremath{\nu}}}_{e}$ events from $^{238}\mathrm{U}$ and $^{232}\mathrm{Th}$, corresponding to a geo ${\overline{\ensuremath{\nu}}}_{e}$ flux of ${3.4}_{\ensuremath{-}0.8...