Calculation of delayed-neutron energy spectra in a quasiparticle random-phase approximation–Hauser-Feshbach model

Kawano, Toshihiko; Möller, P.; Wilson, W.B.

doi:10.1103/physrevc.78.054601

Cited by 56 publications

(53 citation statements)

References 28 publications

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“…As in ref. [17], the current work includes the database evaluations for all fission fragments, using modeled spectra [23,24] for fragments with unmeasured decay spectra.…”

Section: Arxiv:150600583v2 [Nucl-th] 31 Jul 2015mentioning

confidence: 99%

“…(2). The remaining 5% of the fission fragments are modeled [23,24] by extension of the Finite-Range Droplet Model plus Quasi-particle Random Phase Approximation (QRPA). The model has been tuned to account for the so-called pandemonium effect [26] (viz., a very large number of low-energy beta decays to high-lying excited states of the daughter) as well as forbidden transitions, and is supplemented by the nuclear structure library ENSDF [27] where appropriate.…”

Section: Arxiv:150600583v2 [Nucl-th] 31 Jul 2015mentioning

confidence: 99%

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Possible origins and implications of the shoulder in reactor neutrino spectra

et al. 2015

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We analyze within a nuclear database framework the shoulder observed in the antineutrino spectra in current reactor experiments. We find that the ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an analogous shoulder in the aggregate fission beta spectra. In contrast, the JEFF-3.1.1 database does not predict a shoulder for two out of three of the modern reactor neutrino experiments, and the shoulder that is predicted by JEFF-3.1.1 arises from 238 U. We consider several possible origins of the shoulder, and find possible explanations. For example, there could be a problem with the measured aggregate beta spectra, or the harder neutron spectrum at a light-water power reactor could affect the distribution of beta-decaying isotopes. In addition to the fissile actinides, we find that 238 U could also play a significant role in distorting the total antineutrino spectrum. Distinguishing these and quantifying whether there is an anomaly associated with measured reactor neutrino signals will require new short-baseline experiments, both at thermal reactors and at reactors with a sizable epithermal neutron component.Modern reactor neutrino experiments measuring θ 13 , such as Daya Bay [1], RENO [2], and Double Chooz [3], involve detectors both near and far from the reactors. The shape and magnitude of the antineutrino spectra emitted from the reactors have been measured to high accuracy in the near detectors of both Daya Bay and RENO. The Daya Bay near-detector has also provided an absolute determination of the reactor antineutrino flux, and this is consistent in magnitude with the previous world average short-baseline reactor neutrino experiments. As such, the measured magnitude is consistent with a deficit with respect to the most recent estimates [4,5] of the expected reactor antineutrino flux. The absolute magnitude of the RENO flux has yet to be published. However, in the near detector of both RENO and Daya Bay the shapes of the measured spectra are not consistent with the antineutrino spectrum predictions [4,5] that we refer to as the Huber-Mueller model. Most notably, the measured antineutrino spectra exhibit a significant shoulder relative to the model predictions at antineutrino energies ∼ 5 − 7 MeV. The spectra measured at Daya Bay, RENO, and Double Chooz all exhibit this shoulder. Thus, there are two puzzles associated with measured reactor antineutrino spectra: (1) the yield in all short-baseline experiments is lower than current models, and (2) the shape of the measured spectra deviate from these model predictions. However, these two issues are not necessarily related.In the Daya Bay, RENO and Double Chooz experiments the antineutrinos are measured by detecting the positrons produced in inverse beta decay on the protons (ν e + p → n + e + ) in the detector, and the positron energy is reconstructed from the scintillation light created by the kinetic energy of the positron and its annihilation. The antineutrino spectrum S(E ν ) emitted from a reactor is determined by [6] the reactor ther...

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“…As in ref. [17], the current work includes the database evaluations for all fission fragments, using modeled spectra [23,24] for fragments with unmeasured decay spectra.…”

Section: Arxiv:150600583v2 [Nucl-th] 31 Jul 2015mentioning

confidence: 99%

Section: Arxiv:150600583v2 [Nucl-th] 31 Jul 2015mentioning

confidence: 99%

Possible origins and implications of the shoulder in reactor neutrino spectra

et al. 2015

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“…In addition, we use the direct β-spectrum measurements of Rudstam et al [23] to obtain I i (E ν ) for ten nuclides without TAGS data and with incomplete decay schemes. Finally, the ENDF/B-VII.1 decay data sub-library includes theoretical calculations [24] of β-spectra for the most neutron rich nuclides with incomplete decay schemes. Due to limitations in the library's format, the antineutrino spectra are not part of Electron Energy (MeV)…”

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confidence: 99%

Nuclear structure insights into reactor antineutrino spectra

2015

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“…For example, when the β-decay strength function is calculated with the mean-field theory, it gives a population distribution in an initial compound nucleus, from which we can calculate the β-delayed γ and neutron emissions, and fission with Hauser-Feshbach theory [27]. An internal calculation of giant dipole/quadrupole resonances also provides photon strength functions important for the neutron radiative capture process.…”

Section: Discussionmentioning

confidence: 99%

Advances in nuclear reaction calculations by incorporating information from nuclear mean-field theories

Kawano

2017

EPJ Web Conf.

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Abstract. Mean-field model calculations for nuclear structure theories are combined with the statistical Hauser-Feshbach code in order to improve predictive capabilities of nuclear reaction for experimentally unknown cross sections. Utilizing the mean-field calculation results we calculate second moments of matrix elements for the residual interaction. The second moments are applied to a microscopic level density model based on the random matrix theory. An example is shown for the 208 Pb level density calculation.

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Calculation of delayed-neutron energy spectra in a quasiparticle random-phase approximation–Hauser-Feshbach model

Cited by 56 publications

References 28 publications

Possible origins and implications of the shoulder in reactor neutrino spectra

Possible origins and implications of the shoulder in reactor neutrino spectra

Nuclear structure insights into reactor antineutrino spectra

Advances in nuclear reaction calculations by incorporating information from nuclear mean-field theories

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