Antineutrino-deuteron experiment at the Krasnoyarsk reactor

The investigation of antineutrino interaction with matter at the Krasnoyarsk reactor is described. The characteristics of the “Deuteron” detector, the results obtained, and prospects are discussed.     

Status of the CHORUS neutrino oscillation experiment

The CHORUS experiment is designed to search for ν_μ → ν_τ oscillation with a hybrid detector system containing 800 kg nuclear emulsions as target and vertex detector. Run I (320 000 recorded ν_μCC in 1994/5) and more than half of the run II (460 000 ν_μCC in 1996/7) data taking have been successfully completed. Approximately 80 000 events have been analyzed so far, searching for and τ⁻ → h⁻ (nπ⁰) ν_τ decays. No candidate has been found, leading to a limit sin² 2θ_μτ ≤ 4.5 10⁻³ for large Δm².     

Double Chooz project: Status of a reactor experiment aimed at searches for neutrino oscillations

Double Chooz is an experiment that is devoted to searches for reactor-antineutrino oscillations at the CHOOZ nuclear power plant. This project is aimed at measuring the unknown mixing angle θ ₁₃. It is assumed that the value of θ ₁₃ will be extracted from an analysis of the distortion of the antineutrino spectra obtained in relative measurements at two distances from the nuclear reactors by means of two identical detectors. The method makes it possible to minimize systematic errors of the experiment and to improve the sensitivity to the sought parameter. To date, the most stringent constraint on the parameter θ ₁₃ was obtained from the CHOOZ experiment in 1995–1997 [sin²(2θ ₁₃) < 0.19, with the difference of the squares of the neutrino masses being Δm ₁₃ ² = 2.5 × 10^?3 eV²].     

Neutrino-induced deuteron disintegration in an experiment at the Krasnoyarsk nuclear reactor

The results of studying antineutrino interactions with deuterons (CCD and NCD reactions) and hydrogen (CCP) at the Krasnoyarsk underground reactor with the Deuteron detector are presented. The cross sections for NCD and CCD were measured with a precision of 9%. For CCP, the precision is 3%: σ _expt ^NCD =(3.35±0.31)×10^?44 cm²/fission ²³⁵U, σ _expt ^NCD =(1.08±0.09)×10^?44 cm²/fission ²³⁵U, and σ _expt ^NCD =(6.39±0.19)×10^?43 cm²/fission ²³⁵U. The precision of the experimental results is close to the theoretical one and is in good agreement with other experiments. The limit on the parameters of antineutrino oscillations into the sterile state was obtained: Δm ²≤4.7×10^?2 eV² for sin²(2?)=1.0 (68% C.L.). A comparison of the measured and theoretical cross section gives us the neutron-neutron scattering length of a _nn(S)=?17±6 fm in the approach of zero momentum transfers. The weak neutral current constant is in good agreement with the prediction of the Standard Model: G _A ^NC =G _A ^CC /0.932±0.056.     

Mixing MC events in reactor neutrino experiment

In reactor neutrino experiments, the analysis of time correlations between different physical events is an important task. Such analysis can help to understand the physical mechanisms of the signal and background events as well as the details of event selection and background estimation. This study investigates a "sampling and mixing" method used for producing large MC data samples for the Daya Bay reactor neutrino experiment. We designed a simple, generic mixing algorithm and generated large MC data samples for physics analysis from several samples according to their respective event rates. Basic plots based on the mixed data are shown.     

Evidence for muon neutrino oscillation in an accelerator-based experiment

We present results for nu(mu) oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of nu(mu), which we presume have oscillated to nu(tau). The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).     

大亚湾反应堆中微子实验

中微子振荡是目前唯一超出粒子物理标准模型的新现象，它证明了中微子质量不为零，对粒子物理、天体物理与宇宙学均有非常重要的意义．在描述中微子振荡的6个参数中，目前仍有两个未知：交叉混合角θ13与CP相角δ．作者建议在大亚湾反应堆附近建设一个中微子实验站，测量混合角sin^2θ13，在90％的置信度下达到0．01的精度，较过去的实验提高近一个数量级．这将对中微子物理的未来发展提供方向性指导，特别是对理解宇宙中“反物质消失之谜”具有重要意义．     

Mixing MC events in a reactor neutrino experiment

In reactor neutrino experiments, the analysis of time correlations between different physical events is an important task. Such analysis can help to understand the physical mechanisms of the signal and background events as well as the details of event selection and background estimation. This study investigates a "sampling and mixing" method used for producing large MC data samples for the Daya Bay reactor neutrino experiment. We designed a simple, generic mixing algorithm and generated large MC data samples for physics analysis from several samples according to their respective event rates. Basic plots based on the mixed data are shown.     

大亚湾反应堆中微子实验

中微子振荡是目前唯一超出粒子物理标准模型的新现象,它证明了中微子质量不为零,对粒子物理、天体物理与宇宙学均有非常重要的意义.在描述中微子振荡的6个参数中,目前仍有两个未知：交叉混合角θ13与CP相角δ. 作者建议在大亚湾反应堆附近建设一个中微子实验站,测量混合角sin22θ13在90%的置信度下达到0.01 的精度,较过去的实验提高近一个数量级.这将对中微子物理的未来发展提供方向性指导,特别是对理解宇宙中“反物质消失之谜”具有重要意义.     

Limits on neutrino oscillation parameters from the chlorine solar-neutrino experiment

MSW regeneration of solar ν_e in the earth can lead to a seasonal variation in the capture rate in the chlorine solar-neutrino experiment. The absence of such an effect in the data allows us to set a limit on the neutrino oscillation parameters for Δm² near 3 × 10⁻⁶ eV². The limit thus obtained is only weakly dependent on solar-model inputs.     

The NE detector for a long baseline neutrino oscillation experiment

The project of a large underground experiment, N^OE (Neutrino Oscillation Experiment), composed by modules of scintillating fiber calorimeter interleaved with TRD modules, total weight 6.7 ktons, is presented. This apparatus has been optimized for long baseline neutrino oscillation studies, in particular to be sensitive in the region of sin² 2θ and Δm² suggested by the atmospheric neutrino anomaly (fig. 3).     

Indications of neutrino oscillation in a 250 km long-baseline experiment

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.     

The Palo Verde reactor neutrino experiment a test for long baseline neutrino oscillations

Our collaboration has installed a long baseline neutrino oscillation experiment at the Palo Verde Nuclear Generating Station in Arizona. 12 tons of Gd loaded liquid scintillator, in a segmented detector, are used to search for oscillations at 740 m distance to three reactors. The anti-neutrino capture on the proton serves as detection reaction. The experiment is expected to reach a sensitivity of Δm² > 1.3 · 10⁻³ eV² and sin²2Θ > 0.1. Our range of sensitivity is tuned to test the ν_μ ↔ ν_e solution of the atmospheric neutrino anomaly.     

Limit on the electron neutrino magnetic moment from the kuo-sheng reactor neutrino experiment

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred.     

Systematic impact of spent nuclear fuel on θ13 sensitivity at reactor neutrino experiment

Reactor neutrino oscillation experiments, such as Daya Bay, Double Chooz and RENO are designed to determine the neutrino mixing angle θ13 with a sensitivity of 0.01--0.03 in sin2 2θ13 at 90% confidence level, an improvement over the current limit by more than one order of magnitude. The control of systematic uncertainties is critical to achieving the sin2 2θ13 sensitivity goal of these experiments. Antineutrinos emitted from spent nuclear fuel (SNF) would distort the soft part of energy spectrum and may introduce a non-negligible systematic uncertainty. In this article, a detailed calculation of SNF neutrinos is performed taking account of the operation of a typical reactor and the event rate in the detector is obtained. A further estimation shows that the event rate contribution of SNF neutrinos is less than 0.2% relative to the reactor neutrino signals. A global χ2 analysis shows that this uncertainty will degrade the θ13 sensitivity at a negligible level.