Abstract
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era. The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment, in combination with the fission rates of fissile isotopes in the reactor, is used to extract the positron energy spectra resulting from the fission of specific isotopes. This information can be used to produce a precise, data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay. The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method. Consistent results are obtained with other unfolding methods. A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated. Given the reactor fission fractions, the technique can predict the energy spectrum to a 2% precision. In addition, we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.
Highlights
Nuclear reactors are a powerful source of electron antineutrinos and have played a significant role in neutrino physics, including the discovery of neutrinos [1], the measurement of the neutrino mixing angle θ12 and the neutrino mass-squared splitting ∆m221 [2], and the observation of the neutrino oscillation driven by θ13 [3,4,5]
Generation of models of the νe flux and energy spectrum for different reactor types based on the measurement at Daya Bay: 1a) For experiments utilizing commercial low-enriched uranium (LEU) pressurized-water reactors [6, 11, 47], even with fission fractions different from those of Daya Bay, the prediction can be made at 2% precision with very little dependence on other isotopic νe flux models
Comparison to other theoretical models in a variety of possible formats: 2a) The theoretical models can be compared with unfolded νe energy spectra directly using error matrices in the supplemental materials, at the expense of reduced precision from additional unfolding uncertainties. 2b) The comparison between theoretical models and unfolded νe energy spectra can be done with better precision using features of the Wiener-SVD unfolding method. 2c) The comparison can be done by getting prediction of the prompt energy spectrum with better precision using Daya Bay’s detector response matrix
Summary
We are grateful for the ongoing cooperation from the China Guangdong Nuclear Power Group and China Light & Power Company
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