A1 Journal article (refereed)
First-forbidden transitions in the reactor anomaly (2019)

Hayen, L., Kostensalo, J., Severijns, N., & Suhonen, J. (2019). First-forbidden transitions in the reactor anomaly. Physical Review C, 100(5), Article 054323. https://doi.org/10.1103/PhysRevC.100.054323

JYU authors or editors

Publication details

All authors or editorsHayen, L.; Kostensalo, J.; Severijns, N.; Suhonen, J.

Journal or seriesPhysical Review C



Publication year2019


Issue number5

Article number054323

PublisherAmerican Physical Society

Publication countryUnited States

Publication languageEnglish


Publication open accessNot open

Publication channel open access

Publication is parallel published (JYX)https://jyx.jyu.fi/handle/123456789/66520

Publication is parallel publishedhttps://arxiv.org/abs/1805.12259


We describe here microscopic calculations performed on the dominant forbidden transitions in reactor antineutrino spectra above 4 MeV using the nuclear shell model. By taking into account Coulomb corrections in the most complete way, we calculate the shape factor with the highest fidelity and show strong deviations from allowed approximations and previously published results. Despite small differences in the ab initio electron cumulative spectra, large differences on the order of several percent are found in the antineutrino spectra. Based on the behavior of the numerically calculated shape factors we propose a parametrization of forbidden spectra. Using Monte Carlo techniques we derive an estimated spectral correction and uncertainty due to forbidden transitions. We establish the dominance and importance of forbidden transitions in both the reactor anomaly and spectral shoulder analysis with their respective uncertainties. Based on these results, we conclude that a correct treatment of forbidden transitions is indispensable in both the normalization anomaly and spectral shoulder.

Keywordsnuclear physicsparticle physics

Free keywordsbeta decay; electroweak interactions in nuclear physics; fission; neutrino interactions; nuclear reactors; shell model

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Ministry reportingYes

Reporting Year2019

JUFO rating2

Last updated on 2024-25-03 at 13:16