Investigating the Spectral Anomaly with Different Reactor Antineutrino Experiments

TL;DR

This paper explores the spectral anomaly in reactor antineutrino measurements by combining data from highly enriched and commercial reactors to determine if the anomaly is linked to ${}^{235}$U, emphasizing the importance of energy scale accuracy.

Contribution

It proposes a novel experimental approach combining different reactor types to clarify the origin of the spectral anomaly in antineutrino spectra.

Findings

Combining reactor data can distinguish if the anomaly is related to ${}^{235}$U.

A significance level of three sigma or higher is achievable with current experiments.

Energy scale systematics are critical for interpreting spectral anomaly results.

Abstract

The spectral shape of reactor antineutrinos measured in recent experiments shows anomalies in comparison to neutrino reference spectra. New precision measurements of the reactor neutrino spectra as well as more complete input in nuclear data bases are needed to resolve the observed discrepancies between models and experimental results. This article proposes the combination of experiments at reactors which are highly enriched in ${}^{235}$U with commercial reactors with typically lower enrichment to gain new insights into the origin of the anomalous neutrino spectrum. The presented method clarifies, if the spectral anomaly is either solely or not at all related to the predicted ${}^{235}$U spectrum. Considering the current improvements of the energy scale uncertainty of present-day experiments, a significance of three sigma and above can be reached. As an example, we discuss the option of a direct comparison of the measured shape in the currently running Double Chooz near detector and the upcoming Stereo experiment. A quantitative feasibility study emphasizes that a precise understanding of the energy scale systematics is a crucial prerequisite in recent and next generation experiments investigating the spectral anomaly.