Measurement of reactor antineutrino flux and spectrum at RENO

Adil Zohaib ,J W Seo ,J Yoo ,H G Lee ,S Y Kim ,W Kim ,J G Kim ,S G Yoon ,J Y Kim ,In Sung Yeo ,E Kwon ,H Seo ,Dongmin Jung ,Chang Dong Shin ,B S Yang ,D H Moon ,I T Lim ,S Jeon ,J H Kim ,D H Lee ,H I Jang ,Jiwon Choi ,K K Joo ,S B Kim ,J S Jang ,K Ju ,M Y Pac ,I Yu

doi:10.1103/physrevd.104.l111301

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.

Highlights

Unfolding Spill-in rate −0.2 −0.4 Detection eff. −0.6to the Huber and Mueller (HM) prediction
RENO [7,8] and other reactor experiments [9,10,11,12,13,14] have observed an excess of events in the measured inverse beta decay (IBD) prompt energy spectrum at 5 MeV relative to the HM prediction
This paper reports RENO’s first measurement of the reactor νe flux and unfolded spectrum based on 966 094 (116 111) IBD candidate events in the near detector

Summary

Measurement of reactor antineutrino flux and spectrum at RENO

RENO [7,8] and other reactor experiments [9,10,11,12,13,14] have observed an excess of events in the measured inverse beta decay (IBD) prompt energy spectrum at 5 MeV relative to the HM prediction. This paper reports RENO’s first measurement of the reactor νe flux and unfolded spectrum based on 966 094 (116 111) IBD candidate events in the near (far) detector This result provides useful information for unveiling anomalies associated with reactor neutrinos and unknown neutrino properties. The reactor flux-weighted baseline is 419.4 m for the near detector and 1 447.1 m for the far detector

Published by the American Physical Society

Findings

Background