Kim Siyeon

Observation of reactor electron antineutrinos disappearance in the RENO experiment.

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.

Minimal seesaw model with tri/bi-maximal mixing and leptogenesis

Abstract We examine minimal seesaw mechanism in which the masses of light neutrinos are described with tri/bi-maximal mixing in the basis where the charged-lepton Yukawa matrix and heavy Majorana neutrino mass matrix are diagonal. We search for all possible Dirac mass textures which contain at least one zero entry in 3 × 2 matrix and evaluate the corresponding lepton asymmetries. We present the baryon asymmetry in terms of a single low energy unknown, a Majorana CP phase to be clued from neutrinoless double beta decay.

Conflict between the identification of a cosmic neutrino source and the sensitivity to mixing angles in a neutrino telescope

Neutrino fluxes at telescopes depend on both initial fluxes out of astronomical bursts and flavor mixing during their travel to the Earth. However, since the information on the initial composition requires better precision in mixing angles and vice versa, neutrino detection at telescopes cannot provide solutions to both problems by itself. Thus, a probability to be measured at long-baseline oscillation is considered as a complement to the telescope, and problems like source identification and parameter degeneracy are examined under a few assumptions.

Simulations of background sources in AMoRE-I experiment

Abstract The first phase of the Advanced Mo-based Rare process Experiment (AMoRE-I), an experimental search for neutrinoless double beta decay ( 0 ν β β ) of 100Mo in calcium molybdate ( 40 Ca100MoO4) crystal using cryogenic detection techniques, is in preparation at the YangYang underground laboratory (Y2L) in Korea. A GEANT4 based Monte Carlo simulation was performed for the first-phase AMoRE detector and shield configuration. Background sources such as 238U, 232Th, 235U, and 210Pb from inside the crystals, surrounding materials, outer shielding walls of the Y2L cavity were simulated. The estimated background rate in the region of interest was estimated to be 1.5 × 10 − 3 counts/keV/kg/yr (ckky). The effects of random coincidences between backgrounds and two-neutrino double beta decays of 100Mo as a potential background source were estimated to be 2.3 × 10 − 4 ckky.

Pulse shape discrimination capability of metal-loaded organic liquid scintillators for a short-baseline reactor neutrino experiment

A new short-baseline (SBL) reactor neutrino experiment is proposed to investigate a reactor anti-neutrino anomaly. A liquid scintillator (LS) is used to detect anti-neutrinos emitted from a Hanaro reactor, and the pulse shape discrimination (PSD) ability of the metal-loaded organic LSs is evaluated on small-scale laboratory samples. PSD can be affected by selecting different base solvents, and several of the LSs used two different organic base solvents, such as linear alkyl benzene and di-isopropylnaphthalene. For the metallic content, gadolinium (Gd) or lithium (6Li) was loaded into a home-made organic LS and into a commercially available liquid scintillation cocktail. A feasibility study was performed for the PSD using several different liquid scintillation cocktails. In this work, the preparation and the PSD characteristics of a promising candidate, which will be used in an above-ground environment, are summarized and presented.

Four-Neutrino Analysis of 1.5 km Baseline Reactor Antineutrino Oscillations

The masses of sterile neutrinos are not yet known, and depending on the orders of magnitudes, their existence may explain reactor anomalies or the spectral shape of reactor neutrino events at 1.5 km baseline detector. Here, we present four-neutrino analysis of the results announced by RENO and Daya Bay, which performed the definitive measurements of based on the disappearance of reactor antineutrinos at km order baselines. Our results using 3

Non-vanishing U e3 under S 3 symmetry

This work proposes two models of neutrino masses that predict non-zero θ13 under the non-Abelian discrete flavor symmetry

Non-vanishing Ue3 under S3 symmetry

\mathbb{S}_{3}\otimes\mathbb{Z}_{2}

Discrete symmetries and neutrino masses

. We advocate that the size of θ13 is understood as a group theoretical consequence rather than a perturbed effect from the tri-bi-maximal mixing. So, the difference of two models is designed only in terms of the flavor symmetry, by changing the charge assignment of right-handed neutrinos. The PMNS matrix in the first model is obtained from both mass matrices, charged leptons giving rise to non-zero

Seesaw scale and CP phases in a minimal model of leptogenesis

\theta^{l}_{13}