Spectral Structure of Electron Antineutrinos from Nuclear Reactors

TL;DR

This paper investigates the spectral features of electron antineutrinos from nuclear reactors, identifying isotopic origins of spectral excesses and substructures, which are crucial for reactor physics and neutrino measurements.

Contribution

It links spectral anomalies to specific fission isotopes and predicts substructure due to Coulomb effects, advancing understanding of reactor antineutrino spectra.

Findings

Identification of isotopes contributing to spectral excess

Prediction of spectral substructure from Coulomb effects

Implications for reactor physics and neutrino experiments

Abstract

Recent measurements of the positron energy spectrum obtained from inverse beta decay interactions of reactor electron antineutrinos show an excess in the 4 to 6 MeV region relative to current predictions. First-principle calculations of fission and beta decay processes within a typical pressurized water reactor core identify prominent fission daughter isotopes as a possible origin for this excess. These calculations also predict percent-level substructure in the antineutrino spectrum due to Coulomb effects in beta decay. Precise measurement of this substructure can constrain nuclear reactor physics. The substructure can be a systematic uncertainty for measurements utilizing the detailed spectral shape.