Eur. Phys. J. C (2014) 74: 3094
https://doi.org/10.1140/epjc/s10052-014-3094-x

Review

Antineutrino science in KamLAND

KEK, High Energy Accelerator Research Organization, Oho 1-1, Tsukuba, Ibaraki, 305-0801, Japan

^* e-mail: suzuki@post.kek.jp

Received: 5 August 2014
Accepted: 3 September 2014
Published online: 7 October 2014

Abstract

The primary goal of KamLAND is a search for the oscillation of ’s emitted from distant power reactors. The long baseline, typically 180 km, enables KamLAND to address the oscillation solution of the “solar neutrino problem” with ’s under laboratory conditions. KamLAND found fewer reactor events than expected from standard assumptions about propagation at more than 9 confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at more than 5 C.L., and prefers the distortion from neutrino oscillation effects. A three-flavor oscillation analysis of the data from KamLAND and KamLAND + solar neutrino experiments with CPT invariance, yields = [10 eV, 10 eV], tan = [, ], and sin = [, ]. All solutions to the solar neutrino problem except for the large mixing angle region are excluded. KamLAND also demonstrated almost two cycles of the periodic feature expected from neutrino oscillation effects. KamLAND performed the first experimental study of antineutrinos from the Earth’s interior so-called geoneutrinos (geo ’s), and succeeded in detecting geo ’s produced by the decays of U and Th within the Earth. Assuming a chondritic Th/U mass ratio, we obtain events from U and Th, corresponding a geo flux of 10 cm s at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo rate.