The RENO experiment has observed the disappearance of reactor electron antineutrinos, consistent with neutrino oscillations, with a significance of 4.9 standard deviations. Antineutrinos from six 2.8  GW(th) reactors at the Yonggwang Nuclear Power Plant in Korea, are detected by two identical detectors located at 294 and 1383 m, respectively, from the reactor array center. In the 229 d data-taking period between 11 August 2011 and 26 March 2012, the far (near) detector observed 17102 (154088) electron antineutrino candidate events with a background fraction of 5.5% (2.7%). The ratio of observed to expected numbers of antineutrinos in the far detector is 0.920±0.009(stat)±0.014(syst). From this deficit, we determine sin(2)2θ(13)=0.113±0.013(stat)±0.019(syst) based on a rate-only analysis.

An experiment to search for light sterile neutrinos is conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search is done with a detector consisting of a ton of Gd-loaded liquid scintillator in a tendon gallery approximately 24 m from the reactor core. The measured antineutrino event rate is 1976 per day with a signal to background ratio of about 22. The shape of the antineutrino energy spectrum obtained from the eight-month data-taking period is compared with a hypothesis of oscillations due to activesterile antineutrino mixing. No strong evidence of 3+1 neutrino oscillation is found. An excess around the 5 MeV prompt energy range is observed as seen in existing longer-baseline experiments. The mixing parameter sin 2 2θ14 is limited up to less than 0.1 for ∆m The mixing among three neutrinos has been well established by experiments performed in the past two decades since the discovery of neutrino oscillations [1][2][3]. Consistent measurements of the two mass differences and the three mixing angles of the standard, three-neutrino mixing model have been reported by oscillation experiments using atmospheric, solar, reactor, and accelerator neutrinos [4]. Nevertheless, the mass hierarchy, the mass of the lightest neutrino, the Dirac or Majorana nature of the neutrino, and the CP phase are yet to be determined [5].Even though the number of active light neutrinos is limited to three by Z boson decay-width measurements [6], it is still possible to have additional neutrinos if they are sterile. Sterile neutrinos can be identified by the occurrence of activesterile neutrino oscillations. A hint for this is the LSND experiment's report of an observation ofν µ →ν e mixing with a frequency corresponding to a mass-squared difference larger than 0.01 eV 2 [7]. Results from the MiniBooNE's test of the LSND signal are, however, inconclusive [8].In addition to the LSND result, there are two other anomalies that could possibly be signs of active-sterile neutrino oscillations. An apparent ν e disappearance over a baseline of a few meters in the GALLEX and SAGE gallium experiments exposed to radioactive sources was reported [9]; the ratio of the numbers of measured and predicted events is 0.88 ± 0.05. A number of short-baseline reactor antineutrino experiments established limits on the presence of neutrino oscillations with eV mass differences by shape analyses of the measured neutrino energy spectra. Among those experiments, the Bugey experimental limits on sterile neutrinos are the most stringent [10]. Mueller et al. [11] found about a 6% deficit in reactor antineutrino event rates compared with the theoretical expectations for the short-baseline reactor experiments, which is the so-called "reactor antineutrino anomaly" (RAA). It can be interpreted as an active-sterile neutrino oscillation with three active neutrinos plus one or more sterile neutrinos, i.e., a 3 + n ν scenario [12,13], compatible with the LSND result. Recent reactor experiments that measured the θ 13 mixing an...

The RENO experiment has analyzed about 500 live days of data to observe an energy dependent disappearance of reactor νe by comparison of their prompt signal spectra measured in two identical near and far detectors. In the period between August 2011 and January 2013, the far (near) detector observed 31541 (290775) electron antineutrino candidate events with a background fraction of 4.9% (2.8%). The measured prompt spectra show an excess of reactor νe around 5 MeV relative to the prediction from a most commonly used model. A clear energy and baseline dependent disappearance of reactor νe is observed in the deficit of the observed number of νe. Based on the measured far-to-near ratio of prompt spectra, we obtain sin 2 2θ13 = 0. The reactor ν e disappearance has been firmly observed to determine the smallest neutrino mixing angle θ 13 [1-3]. All of the three mixing angles in the Pontecorvo-MakiNakagawa-Sakata matrix [4,5] have been measured to provide a comprehensive picture of neutrino transformation. The successful measurement of a rather large θ 13 value opens the possibility of searching for CP violation in the leptonic sector and determining the neutrino mass ordering. Appearance of ν e from an accelerator ν µ beam is also observed by the T2K [6] and NOνA [7] experiments.Using the ν e survival probability P [8], reactor experiments with a baseline distance of ∼1 km can determine the mixing angle θ 13 and an effective squared-massdifference ∆m where ∆ ij ≡ 1.267∆m 2 ij L/E, E is the ν e energy in MeV, and L is the distance between the reactor and detector in meters.The first measurement of θ 13 by RENO was based on the rate-only analysis of deficit found in ∼220 live days of data [1]. The oscillation frequency |∆m 2 ee | in the measurement was approximated by the measured value |∆m 2 31 | assuming the normal ordering in the ν µ disappearance [10]. In this Letter, we present a more precisely measured value of θ 13 and our first determination of |∆m 2 ee |, based on the rate, spectral and baseline information (rate+spectrum analysis) of reactor ν e disappearance using ∼500 live days of data. The Daya Bay collaboration has also reported spectral measurements [11].The RENO uses identical near and far ν e detectors located at 294 m and 1383 m, respectively, from the center of six reactor cores of the Hanbit (known as Yonggwang) Nulcear Power Plant. The far (near) detector is under a 450 m (120 m) of water equivalent overburden. Six pressurized water reactors, each with maximum thermal output of 2.8 GW th , are situated in a linear array spanning 1.3 km with equal spacings. The reactor flux-weighted baseline is 410.6 m for the near detector and 1445.7 m for the far detector.The reactor ν e is detected through the inverse beta decay (IBD) interaction, ν e + p → e + + n, with free protons in hydrocarbon liquid scintillator (LS) with 0.1% Gadolinium (Gd) as a target. The coincidence of a prompt positron signal and a mean time of ∼28 µs delayed signal from neutron capture by Gd (n-Gd) provides the distinctive IBD signatur...

The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber with an active volume of 7.2× 6.1× 7.0 m3. It is installed at the CERN Neutrino Platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 GeV/c to 7 GeV/c. Beam line instrumentation provides accurate momentum measurements and particle identification. The ProtoDUNE-SP detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment, and it incorporates full-size components as designed for that module. This paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. It presents the first results on ProtoDUNE-SP's performance, including noise and gain measurements, dE/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. The measured values meet or exceed the specifications for the DUNE far detector, in several cases by large margins. ProtoDUNE-SP's successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design.

The deep underground neutrino experiment (DUNE), a 40-kton underground liquid argon time projection chamber experiment, will be sensitive to the electron-neutrino flavor component of the burst of neutrinos expected from the next Galactic core-collapse supernova. Such an observation will bring unique insight into the astrophysics of core collapse as well as into the properties of neutrinos. The general capabilities of DUNE for neutrino detection in the relevant few- to few-tens-of-MeV neutrino energy range will be described. As an example, DUNE’s ability to constrain the $$\nu _e$$ ν e spectral parameters of the neutrino burst will be considered.