# Reactor antineutrino shoulder explained by energy scale nonlinearities?

## TL;DR

This paper investigates whether nonlinearities in the energy scale calibration of reactor antineutrino detectors can explain the observed spectral distortions, suggesting calibration issues as an alternative to new physics or spectrum models.

## Contribution

The study demonstrates that a small, about 1%, nonlinear energy scale deviation can account for the spectral shoulder observed in reactor antineutrino experiments, within calibration uncertainties.

## Key findings

- A 1% energy scale deviation reproduces the spectral distortion.
- The deviation remains consistent with calibration data and Boron 12 spectrum.
- Calibration uncertainties could explain the observed anomaly.

## Abstract

The Daya Bay, Double Chooz and RENO experiments recently observed a significant distortion in their detected reactor antineutrino spectra, being at odds with the current predictions. Although such a result suggests to revisit the current reactor antineutrino spectra modeling, an alternative scenario, which could potentially explain this anomaly, is explored in this letter. Using an appropriate statistical method, a study of the Daya Bay experiment energy scale is performed. While still being in agreement with the {\gamma} calibration data and Boron 12 measured spectrum, it is shown that a O(1%) deviation of the energy scale reproduces the distortion observed in the Daya Bay spectrum, remaining within the quoted calibration uncertainties. Potential origins of such a deviation, which challenge the energy calibration of these detectors, are finally discussed.