Measurement of reactor antineutrino flux and spectrum at RENO

The RENO experiment reports measured flux and energy spectrum of reactor electron antineutrinos nu over bar e from the six reactors at Hanbit Nuclear Power Plant. The measurements use 966 094 116 111 nu over bar 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 o5.852 1 0.094 thorn x 10-43 cm2/fission, corresponding to 0.941 10.015 of the prediction by the Huber and Mueller (HM) model. A reactor nu over bar 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 nu over bar 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 nu over bar e models.