The RENO experiment reports more precisely measured values of θ_{13} and |Δm_{ee}^{2}| using ∼2200 live days of data. The amplitude and frequency of reactor electron antineutrino (νover ¯_{e}) ...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) νover ¯_{e} candidate events with a background fraction of 4.8% (2.0%). A clear energy and baseline dependent disappearance of reactor νover ¯_{e} is observed in the deficit of the measured number of νover ¯_{e}. Based on the measured far-to-near ratio of prompt spectra, we obtain sin^{2}2θ_{13}=0.0896±0.0048(stat)±0.0047(syst) and |Δm_{ee}^{2}|=2.68±0.12(stat)±0.07(syst)×10^{-3} eV^{2}.
We report a fuel-dependent reactor electron antineutrino (νover ¯_{e}) yield using six 2.8 GW_{th} reactors in the Hanbit nuclear power plant complex, Yonggwang, Korea. The analysis uses 850 666 ...νover ¯_{e} 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 6.6σ. 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} 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 to 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
bstract
The Reactor Experiment for Neutrino Oscillation (RENO) experiment has been taking data using two identical liquid scintillator detectors since August 2011. The experiment has observed the ...disappearance of reactor neutrinos in their interactions with free protons, followed by neutron capture on hydrogen (n-H). Based on 1500 live days of data taken with 16.8 GW
th
reactors at the Hanbit Nuclear Power Plant in Korea, the near (far) detector observes 567690 (90747) electron antineutrino candidate events with the n-H data. This provides an independent measurement of neutrino mixing angle
θ
13
and a consistency check on the validity of the result obtained from the data with neutron capture on Gadolinium (n-Gd). Furthermore, it provides an important cross-check on the systematic uncertainties of the n-Gd measurement. Based on a rate-only analysis, we obtain sin
2
2
θ
13
= 0
.
086 ± 0
.
008(stat
.
) ± 0
.
014(syst
.
). The combination of this result with that of n-Gd is also reported.
It has been reported that Pi2 pulsations can be excited under extremely quiet geomagnetic conditions (Kp=0). However, there have been few comprehensive reports of Pi2 pulsations in such a near ground ...state magnetosphere. To understand the characteristics of quiet‐time Pi2 pulsations, we statistically examined Pi2 events observed on the nightside between 1800 and 0600 local time at the low‐latitude Bohyun (BOH, L = 1.35) station in South Korea. We chose year 2008 for analysis because geomagnetic activity was unusually low in that year. A total of 982 Pi2 events were identified when Kp≤1. About 80% of the Pi2 pulsations had a period between 110 and 300 s, which significantly differs from the conventional Pi2 period from 40 to 150 s. Comparing Pi2 periods and solar wind conditions, we found that Pi2 periods decrease with increasing solar wind speed, consistent with the result of Troitskaya (1967). The observed wave properties are discussed in terms of plasmaspheric resonance, which has been proposed for Pi2 pulsations in the inner magnetosphere. We also found that Pi2 pulsations occur quasi‐periodically with a repetition period of ∼23–38 min. We will discuss what determines such a recurrence time of Pi2 pulsations under quiet geomagnetic conditions.
Key Points
Pi2 pulsations during quiet geomagnetic conditions
Pi2 frequencies depending on solar wind speeds
Quasi‐periodic Pi2 pulsations with an occurrence rate of about 23‐53 min
Summary
The wide geographic spread of Eurasian Goose/Guangdong lineage highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses by wild birds is of great concern. In December 2014, an H5N8 HPAI ...clade 2.3.4.4 Group A (2.3.4.4A) virus was introduced to North America. Long‐distance migratory wild aquatic birds between East Asia and North America, such as Northern Pintail (Anas acuta), were strongly suspected of being a source of intercontinental transmission. In this study, we evaluated the pathogenicity, infectivity and transmissibility of an H5N8 HPAI clade 2.3.4.4A virus in Northern Pintails and compared the results to that of an H5N1 HPAI clade 2.3.2.1 virus. All of Northern Pintails infected with either H5N1 or H5N8 virus lacked clinical signs and mortality, but the H5N8 clade 2.3.4.4 virus was more efficient at replicating within and transmitting between Northern Pintails than the H5N1 clade 2.3.2.1 virus. The H5N8‐infected birds shed high titre of viruses from oropharynx and cloaca, which in the field supported virus transmission and spread. This study highlights the role of wild waterfowl in the intercontinental spread of some HPAI viruses. Migratory aquatic birds should be carefully monitored for the early detection of H5 clade 2.3.4.4 and other HPAI viruses.
We report a search result for a light sterile neutrino oscillation with roughly 2200 live days of data in the RENO experiment. The search is performed by electron antineutrino (νe) disappearance ...taking place between six 2.8 GW th reactors and two identical detectors located at 294 m (near) and 1383 m (far) from the center of the reactor array. A spectral comparison between near and far detectors can explore reactor νe oscillations to a light sterile neutrino. An observed spectral difference is found to be consistent with that of the three-flavor oscillation model. This yields limits on sin 22θ14 in the 10−4 ≲ | Δm412 | ≲ 0.5 eV2 region, free from reactor νe flux and spectrum uncertainties. The RENO result provides the most stringent limits on sterile neutrino mixing at | Δm412 | ≲ 0.002 eV2 using the νe disappearance channel.
Plasmaspheric virtual resonance (PVR) model has been proposed as one of source mechanisms for low‐latitude Pi2 pulsations. Since PVR‐associated Pi2 pulsations are not localized inside the ...plasmasphere, simultaneous multipoint observations inside and outside the plasmasphere require to test the PVR model. Until now, however, there are few studies using simultaneous multisatellite observations inside and outside the plasmasphere for understanding the radial structure of Pi2 pulsation. In this study, we focus on the Pi2 event observed at low‐latitude Bohyun (BOH, L = 1.35) ground station in South Korea in the postmidnight sector (magnetic local time (MLT) = 3.0) for the interval from 1730 to 1900 UT on 12 March 2013. By using electron density derived from the frequency of the upper hybrid waves detected at Van Allen Probe‐A (VAP‐A) and Van Allen Probe‐B (VAP‐B), the plasmapause is identified. At the time of the Pi2 event, VAP‐A was outside the plasmasphere near midnight (00:55 MLT and L =∼ 6), while VAP‐B was inside the plasmasphere in the postmidnight sector (02:15 MLT and L =∼ 5). VAP‐B observed oscillations in the compressional magnetic field component (Bz) and the dawn‐to‐dusk electric field component (Ey), having high coherence with the BOH Pi2 pulsation in the H component. The H‐Bz and H‐Ey cross phases at VAP‐B inside the plasmasphere were near −180° and −90°, respectively. These phase relationships among Bz, Ey, and H are consistent with a radially standing oscillation of the fundamental mode reported in previous studies. At VAP‐A outside the plasmasphere, Bz oscillations were highly correlated with BOH Pi2 pulsations with ∼−180° phase delay, and the H‐Ey cross phase is near −90°. From these two‐satellite observations, we suggest that the fundamental PVR mode is directly detected by VAP‐A and VAP‐B.
Key Points
Multipoint observations of Pi2 pulsations in space
Plasmaspheric virtual resonances for Pi2 pulsations
Radial mode structure of Pi2 pulsation
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) reactor ν¯e candidate events with 2.8% (4.9%) background in the near (far) detector. The observed visible positron spectra from the reactor ν¯e events in both detectors show a discrepancy around 5 MeV with regard to the prediction from the current reactor ν¯e model. Based on a far-to-near ratio measurement using the spectral and rate information, we have obtained sin22θ13=0.082±0.009(stat.)±0.006(syst.) and |Δmee2|=2.62−0.23+0.21(stat.)−0.13+0.12(syst.)×10−3 eV2.
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