Improved estimate of the cross section for inverse beta decay

TL;DR

This paper refines the inverse beta decay cross section calculation by enforcing vector current conservation, resulting in lower estimates that impact neutrino flux measurements and sterile neutrino searches.

Contribution

It provides a more accurate cross section estimate for inverse beta decay by ensuring vector current conservation, affecting neutrino flux and oscillation analyses.

Findings

Lower cross section estimates near threshold

Revised antineutrino flux predictions for geological sources

Adjusted event rates for sterile neutrino searches and reactor anomalies

Abstract

The hypothesis of the conserved vector current, relating the vector weak and isovector electromagnetic currents, plays a fundamental role in quantitative description of neutrino interactions. Despite being experimentally confirmed with great precision, it is not fully implemented in existing calculations of the cross section for inverse beta decay, the dominant mechanism of antineutrino scattering at energies below a few tens of MeV. In this article, I estimate the corresponding cross section and its uncertainty, ensuring conservation of the vector current. While converging to previous calculations at energies of several MeV, the obtained result is appreciably lower and predicts more directional positron production near the reaction threshold. These findings suggest that in the current estimate of the flux of geologically produced antineutrinos the 232Th and 238U components may be underestimated by 6.1 and 3.7%, respectively. The proposed search for light sterile neutrinos using a 144Ce--144Pr source is predicted to collect the total event rate lower by 3% than previously estimated and to observe a spectral distortion that could be misinterpreted as an oscillation signal. In reactor-antineutrino experiments, together with a re-evaluation of the positron spectra, the predicted event rate should be reduced by 0.9%, diminishing the size of the reported anomaly.