Measurement of Reactor Antineutrino Flux and Spectrum at RENO

TL;DR

The RENO experiment measured reactor antineutrino flux and spectrum, revealing a deficit in predicted yield and an excess around 6 MeV, which challenges existing reactor neutrino models and aids future neutrino research.

Contribution

This study provides the first detailed measurement of reactor antineutrino flux and spectrum at RENO, highlighting discrepancies with theoretical models and offering data for refining neutrino physics and reactor models.

Findings

Measured IBD yield is 0.941 of the HM prediction.

Detected a clear excess around 6 MeV in the neutrino spectrum.

Revealed a significant flux deficit compared to models.

Abstract

The RENO experiment reports measured flux and energy spectrum of reactor electron antineutrinos\,($\overline{\nu}_e$) from the six reactors at Hanbit Nuclear Power Plant. The measurements use 966\,094\,(116\,111)\,$\overline{\nu}_e$ candidate events with a background fraction of 2.39\%\,(5.13\%), acquired in the near\,(far) detector, from August 2011 to March 2020. The inverse beta decay (IBD) yield is measured as (5.852$\,\pm\,$0.124$) \times 10^{-43}$\,cm$^2$/fission, corresponding to 0.941\,$\pm$ 0.019 of the prediction by the Huber and Mueller (HM) model. A reactor $\overline{\nu}_e$ spectrum is obtained by unfolding a measured IBD prompt spectrum. The obtained neutrino spectrum shows a clear excess around 6\,MeV relative to the HM prediction. The obtained reactor $\overline{\nu}_e$ spectrum will be useful for understanding unknown neutrino properties and reactor models. The observed discrepancies suggest the next round of precision measurements and modification of the current reactor $\overline{\nu}_e$ models.