Study of $\mathbf{\beta }$ Decay Shape Factors in First-Forbidden Transitions with $\mathbf{\Delta }{\mathbf{I}}^{\mathbf{\pi }}=0^{-}$ for Reactor Antineutrino Spectra Predictions

Abstract

The electron spectra of the $\beta$ decays of ${}^{92}$Rb and ${}^{142}$Cs, key contributors to the reactor antineutrino spectrum, were measured at the IGISOL facility using radioactive beams of high isotopic purity. The shapes of the measured $\beta$ spectra were compared with various $\beta$ shape models, including first-forbidden correction factors for $\Delta I^{\pi }=0^{-}$ ground-state to ground-state transitions. Comparisons with previous experimental results are also provided. The shapes of the newly measured $\beta$ spectra are well reproduced employing feedings extracted from total absorption gamma spectroscopy measurements.

20 pages, 13 figures

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• The Reactor Antineutrino Anomaly
• Updated Summation Model: An Improved Agreement with the Daya Bay Antineutrino Fluxes
• Stereo neutrino spectrum of 235U fission rejects sterile neutrino hypothesis
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