[en] The disappearance of reactor anti ν_e observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion σ_r_e_l. Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of anti ν_e acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: 2.38 x 10"-"1"7 < σ_r_e_l < 0.23. Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: 10"-"1"4 < or similar σ_r_e_l < 0.23, and an upper limit of σ_r_e_l < 0.20 (which corresponds to σ_x >or similar 10"-"1"1 cm) is obtained. All limits correspond to a 95% C.L. Furthermore, the effect due to the wave packet nature of neutrino oscillation is found to be insignificant for reactor antineutrinos detected by the Daya Bay experiment thus ensuring an unbiased measurement of the oscillation parameters sin"22θ_1_3 and Δm"2_3_2 within the plane wave model. (orig.)

[en] The antineutrino flux from spent nuclear fuel (SNF) is an important source of uncertainty when making estimates of a reactor neutrino flux. However, to determine the contribution from SNF, sufficient data is needed such as the amount of spent fuel in the pool, the time after discharged from the reactor core, the burnup of each assembly, and the antineutrino spectrum of each isotope in the SNF. A method to calculate this contribution is proposed. A reactor simulation code verified against experimental data has been used to simulate fuel depletion by taking into account more than 2000 isotopes and fission products, the quantity of SNF in each of the six spent fuel pools, and the time variation of the antineutrino spectra after SNF discharging from the core. Results show that the SNF contribution to the total antineutrino flux is about 0.26%–0.34%, and the shutdown impact is about 20%. The SNF spectrum alters the softer part of the antineutrino spectra, and the maximum contribution from the SNF is about 3.0%. Nevertheless, there is an 18% difference between the line evaluate method and under evaluate method. In addition, non-equilibrium effects are also discussed, and the results are compatible considering the uncertainties. - Highlights: • Spend nuclear fuel (SNF) antineutrino contribution is important source in reactor antineutrino experiment, and a method was proposed to evaluate the contribution of spent nuclear fuel. • The shutdown impact was very large and about 20%, it should be taken into account when doing the SNF calculation. • Non-equilibrium effects are also discussed.

[en] The Daya Bay Experiment consists of eight identically designed detectors located in three underground experimental halls named as EH1, EH2, EH3, with 250, 265 and 860 meters of water equivalent vertical overburden, respectively. Cosmic muon events have been recorded over a two-year period. The underground muon rate is observed to be positively correlated with the effective atmospheric temperature and to follow a seasonal modulation pattern. The correlation coefficient α, describing how a variation in the muon rate relates to a variation in the effective atmospheric temperature, is found to be α_EH1 = 0.362±0.031, α_EH2 = 0.433±0.038 and α_EH3 = 0.641±0.057 for each experimental hall.

[en] The Daya Bay Reactor Neutrino Experiment was designed to achieve a sensitivity on the value of sin²2θ₁₃ to better than 0.01 at 90% CL. The experiment consists of eight antineutrino detectors installed underground at different baselines from six nuclear reactors. With data collected with six antineutrino detectors for 55 days, Daya Bay announced the discovery of a non-zero value for sin²2θ₁₃ with a significance of 5.2 standard deviations in March 2012. The most recent analysis with 139 days of data acquired in a six-detector configuration yields sin²2θ₁₃=0.089±0.010(stat.)±0.005(syst.), which is the most precise measurement of sin²2θ₁₃ to date

[en] The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle θ₁₃ with a sensitivity better than 0.01 in the parameter sin²2θ₁₃ at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties are smaller than requirements.

[en] The Daya Bay experiment consists of functionally identical antineutrino detectors immersed in pools of ultrapure water in three well-separated underground experimental halls near two nuclear reactor complexes. These pools serve both as shields against natural, low-energy radiation, and as water Cherenkov detectors that efficiently detect cosmic muons using arrays of photomultiplier tubes. Each pool is covered by a plane of resistive plate chambers as an additional means of detecting muons. Design, construction, operation, and performance of these muon detectors are described