The RENO experiment reports more precisely measured values of θ13 and |∆m 2 ee | using ∼2 200 live days of data. The amplitude and frequency of reactor electron antineutrino (νe) oscillation are measured by comparing the prompt signal spectra obtained from two identical near and far detectors. In the period between August 2011 and February 2018, the far (near) detector observed 103 212 (850 666) νe candidate events with a background fraction of 4.8% (2.0%). A clear energy and baseline dependent disappearance of reactor νe is observed in the deficit of the measured number of νe. Based on the measured far-to-near ratio of prompt spectra, we obtain sin 2 2θ13 = 0.0896 ± 0.0048(stat) ± 0.0047(syst) and |∆m 2 ee | = [2.68 ± 0.12(stat) ± 0.07(syst)] × 10 −3 eV 2 .

The Reactor Experiment for Neutrino Oscillation (RENO) has been taking electron antineutrino (ν e ) data from the reactors in Yonggwang, Korea, using two identical detectors since August 2011. Using roughly 500 live days of data through January 2013 we observe 290 775 (31 514) reactorν e candidate events with 2.8% (4.9%) background in the near (far) detector. The observed visible positron spectra from the reactorν e events in both detectors show a discrepancy around 5 MeV with regard to the prediction from the current reactorν e model. Based on a far-to-near ratio measurement using the spectral and rate information, we have obtained sin 2 2θ 13 ¼ 0.082 AE 0.009ðstat:Þ AE 0.006ðsyst:Þ and jΔm

We report a fuel-dependent reactor electron antineutrino (νe) yield using six 2.8 GW th reactors in the Hanbit nuclear power plant complex, Yonggwang, Korea. The analysis uses 850 666 νe candidate events with a background fraction of 2.0 % acquired through inverse beta decay (IBD) interactions in the near detector for 1807.9 live days from August 2011 to February 2018. Based on multiple fuel cycles, we observe a fuel 235 U dependent variation of measured IBD yields with a slope of (1.51 ± 0.23) × 10 −43 cm 2 /fission and measure a total average IBD yield of (5.84 ± 0.13) × 10 −43 cm 2 /fission. The hypothesis of no fuel-dependent IBD yield is ruled out at 6.6 σ. The observed IBD yield variation over 235 U isotope fraction does not show significant deviation from the Huber-Mueller (HM) prediction at 1.3 σ. The measured fuel-dependent variation determines IBD yields of (6.15 ± 0.19) × 10 −43 cm 2 /fission and (4.18 ± 0.26) × 10 −43 cm 2 /fission for two dominant fuel isotopes 235 U and 239 Pu, respectively. The measured IBD yield per 235 U fission shows the largest deficit relative to the HM prediction. Reevaluation of the 235 U IBD yield per fission may mostly solve the Reactor Antineutrino Anomaly (RAA) while 239 Pu is not completely ruled out as a possible contributor of the anomaly. We also report a 2.9 σ correlation between the fractional change of the 5 MeV excess and the reactor fuel isotope fraction of 235 U.A definitive measurement of the smallest neutrino mixing angle θ 13 is a tremendous success in neutrino physics during the last decade [1,2]. The measurement has been achieved by comparing the observed ν e fluxes with detectors placed at two different distances from the reactors. As reactor ν e experiments suffer from large reactor related uncertainties of the expected ν e flux and energy spectrum [3][4][5][6][7], identical detector configuration is essential to cancel out the systematic uncertainties. The RAA, ∼6 % deficit of measured ν e flux compared to the HM prediction, is an intriguing mystery in current neutrino physics research and needs to be understood [4][5][6][8][9][10][11]. There have been numerous attempts to explain this anomaly by incorrect inputs to the fission β spectrum conversion, deficiencies in nuclear databases, underestimated uncertainties of reactor ν e model, and the existence of sterile neutrinos [3,[12][13][14][15][16][17][18][19]. Moreover, all of ongoing reactor ν e experiments have observed a 5 MeV excess in the IBD prompt spectrum with respect to the expected one [8,9,20,21]. This suggests that reactor ν e model is not complete at all.In commercial nuclear reactor power plants, almost all (> 99 %)ν e 's are produced through thousands of β-decay branches of fission fragments from 235 U, 239 Pu, 238 U, and 241 Pu. The ν e flux calculation is based on the inversion of spectra of the β-decay electrons of the thermal fissions which were measured in 1980s at ILL [10,11]. The reactor ν e models using these measurements as inputs have large uncertainties [5][6][7]. Therefore, ree...

We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.

The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background U and Th in the liquid scintillator can be controlled to 10 g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If eV , JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3 (2 ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure using B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of reported by solar neutrino experiments and the KamLAND experiment.

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We show that a general solution to the extended holomorphic anomaly equations for the open topological string on D-branes in a Calabi-Yau manifold, recently written down by Walcher in arXiv:0705.4098, is obtained from the general solution to the holomorphic anomaly equations for the closed topological string on the same manifold, by shifting the closed string moduli by amounts proportional to the 't Hooft coupling.

JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day (cpd), therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration to reduce at minimum the impact of natural radioactivity. We describe our efforts for an optimized experimental design, a careful material screening and accurate detector production handling, and a constant control of the expected results through a meticulous Monte Carlo simulation program. We show that all these actions should allow us to keep the background count rate safely below the target value of 10 Hz (i.e. ∼1 cpd accidental background) in the default fiducial volume, above an energy threshold of 0.7 MeV.