2013/08/02 by A. Gando, Y. Gando, H. Hanakago +43 · 1 voice · 4 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Atomic and Subatomic Physics Research #Neutrino Physics Research
paper · pdf · doi:10.1103/physrevd.88.033001
openalex publication_date 2013/08/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
The recent long-term shutdown of Japanese nuclear reactors has resulted in a significantly reduced reactor \ensuremathνe flux at KamLAND. This running condition provides a unique opportunity to confirm and constrain backgrounds for the reactor \ensuremathνe oscillation analysis. The data set also has improved sensitivity for other \ensuremathνe signals, in particular \ensuremathνe's produced in \ensuremathβ-decays from 238U and 232Th within the Earth's interior, whose energy spectrum overlaps with that of reactor \ensuremathνe's. Including constraints on \ensuremathθ13 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 tan2\ensuremathθ12=0.436_\ensuremath-0.025+0.029, \ensuremathΔm212=7.53_\ensuremath-0.18+0.18\ifmmode×\else\texttimes\fi10^\ensuremath-5 eV2, and sin2\ensuremathθ13=0.023_\ensuremath-0.002+0.002. Assuming a chondritic Th/U mass ratio, we obtain 116_\ensuremath-27+28 \ensuremathνe events from 238U and 232Th, corresponding to a geo \ensuremathνe flux of 3.4_\ensuremath-0.8+0.8\ifmmode×\else\texttimes\fi106 cm^\ensuremath-2 s^\ensuremath-1 at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo \ensuremathνe rate.