Weak Magnetism Correction to Allowed Beta-decay for Reactor Antineutrino Spectra

Abstract

The weak magnetism correction and its uncertainty to nuclear beta-decay play a major role in determining the significance of the reactor neutrino anomaly. Here we examine the common approximation used for one-body weak magnetism in the calculation of fission antineutrino spectra, wherein matrix elements of the orbital angular momentum operator contribution to the magnetic dipole current are assumed to be proportional to those of the spin operator. Although we find this approximation invalid for a large set of nuclear structure situations, we conclude that it is valid for the relevant allowed beta-decays between fission fragments. In particular, the uncertainty in the fission antineutrino due to the uncertainty in the one-body weak magnetism correction is found to be less than 1%. Thus, the dominant uncertainty from weak magnetism for reactor neutrino fluxes lies in the uncertainty in the two-body meson-exchange magnetic dipole current.

arXiv comment10 page, 9 figures

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• Impact of Fission Neutron Energies on Reactor Antineutrino Spectra
• Mapping reactor neutrino spectra from TAO to JUNO
• Improved Measurement of the Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay
• New Realization of the Conversion Calculation for Reactor Antineutrino Fluxes
• Analog-antianalog isospin mixing in ${}^{47}$K ${\beta }^{-}$ decay