| Summary: | Nuclear reactors are the most intense man-made source of antineutrinos, providing a useful tool for the study of these particles. Oscillation due to the neutrino mixing angle ${{\theta }_{13}}$ is revealed by the disappearance of reactor ${{\bar{\nu }}_{e}}$ over ∼km distances. Use of additional identical detectors located near nuclear reactors reduce systematic uncertainties related to reactor ${{\bar{\nu }}_{e}}$ emission and detector efficiency, significantly improving the sensitivity of oscillation measurements. The Double Chooz, RENO, and Daya Bay experiments set out in search of ${{\theta }_{13}}$ using these techniques. All three experiments have recently observed reactor ${{\bar{\nu }}_{e}}$ disappearance, and have estimated values for ${{\theta }_{13}}$ of 9.3 ^◦ ± 2.1°, 9.2 ^◦ ± 0.9°, and 8.7 ^◦ ± 0.4° respectively. The energy-dependence of ${{\bar{\nu }}_{e}}$ disappearance has also allowed measurement of the effective neutrino mass difference, $\mid \Delta m_{ee}^{2}\mid $ ≈ $\mid \Delta m_{31}^{2}\mid $ . Comparison with $\mid \Delta m_{\mu \mu }^{2}\mid $ ≈ $\mid \Delta m_{32}^{2}\mid $ from accelerator ${{\nu }_{\mu }}$ measurements supports the three-flavor model of neutrino oscillation. The current generation of reactor ${{\bar{\nu }}_{e}}$ experiments are expected to reach ∼3% precision in both ${{\theta }_{13}}$ and $\mid \Delta m_{ee}^{2}\mid $ . Precise knowledge of these parameters aids interpretation of planned ${{\nu }_{\mu }}$ measurements, and allows future experiments to probe the neutrino mass hierarchy and possible CP-violation in neutrino oscillation. Absolute measurements of the energy spectra of ${{\bar{\nu }}_{e}}$ deviate from existing models of reactor emission, particularly in the range of 5–7 MeV.
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