L. J. Wen

Determination of the neutrino mass hierarchy at an intermediate baseline

It is generally believed that neutrino mass hierarchy can be determined at a long baseline experiment, often using accelerator neutrino beams. Reactor neutrino experiments at an intermediate baseline have the capability to distinguish normal or inverted hierarchy. Recently, it has been demonstrated that the mass hierarchy could possibly be identified using Fourier transform to the L/E spectrum if the mixing angle sin(2)(2 theta(13)) > 0.02. In this study, a more sensitive Fourier analysis is introduced. We found that an ideal detector at an intermediate baseline (similar to 60 km) could identify the mass hierarchy for a mixing angle sin(2)(2 theta(13)) > 0.005, without requirements on accurate information of reactor neutrino spectra and the value of Delta m(32)(2).

Experimental Requirements to Determine the Neutrino Mass Hierarchy Using Reactor Neutrinos

This paper presents experimental requirements to determine the neutrino mass hierarchy using reactor neutrinos. The detector shall be located at a baseline around 58 km from the reactor(s) to measure the energy spectrum of electron antineutrinos ((nu)over bar(e)) precisely. By applying Fourier cosine and sine transforms to the L/E spectrum, features of the neutrino mass hierarchy can be extracted from the vertical bar Delta m(31)(2)vertical bar and vertical bar Delta m(32)(2)vertical bar oscillations. To determine the neutrino mass hierarchy above 90% probability, requirements to the baseline, the energy resolution, the energy scale uncertainty, the detector mass, and the event statistics are studied at different values of sin(2)(2 theta(13)).

Neutrino oscillation studies with reactors

The observation of neutrino oscillations indicates that neutrinos have mass and that their flavours are quantum mechanical mixtures. Here, the authors review the past, present and future contributions of nuclear reactor-based neutrino oscillation experiments, their accomplishments and the remaining challenges.

Production of a gadolinium-loaded liquid scintillator for the Daya Bay reactor neutrino experiment

We report on the production and characterization of liquid scintillators for the detection of electron antineutrinos by the Daya Bay reactor neutrino experiment. A 185 tons of gadolinium-loaded (0.1% by mass) liquid scintillator (Gd-LS) and a 200 tons of unloaded liquid scintillator (LS) were successfully produced from a linear-alkylbenzene (LAB) solvent in 6 months. The scintillator properties, the production and purification systems, and the quality assurance and control (QA/QC) procedures are described

PMT waveform modeling at the Daya Bay experiment

Detailed measurements of Hamamatsu R5912 photomultiplier signals are presented, including the single photoelectron charge response, waveform shape, nonlinearity, saturation, overshoot, oscillation, prepulsing, and afterpulsing. The results were used to build a detailed model of the PMT signal characteristics over a wide range of light intensities. Including the PMT model in simulated Daya Bay particle interactions shows no significant systematic effects that are detrimental to the experimental sensitivity.

Assembly and Installation of the Daya Bay Antineutrino Detectors

The Daya Bay reactor antineutrino experiment is designed to make a precision measurement of the neutrino mixing angle θ_(13), and recently made the definitive discovery of its non-zero value. It utilizes a set of eight, functionally identical antineutrino detectors to measure the reactor flux and spectrum at baselines of ~ 300–2000 m from the Daya Bay and Ling Ao Nuclear Power Plants. The Daya Bay antineutrino detectors were built in an above-ground facility and deployed side-by-side at three underground experimental sites near and far from the nuclear reactors. This configuration allows the experiment to make a precision measurement of reactor antineutrino disappearance over km-long baselines and reduces relative systematic uncertainties between detectors and nuclear reactors. This paper describes the assembly and installation of the Daya Bay antineutrino detectors.

Simulation of natural radioactivity backgrounds in the JUNO central detector

The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment proposed to determine the neutrino mass hierarchy and probe the fundamental properties of neutrino oscillation. The JUNO central detector is a spherical liquid scintillator detector with 20 kton flducial mass. It is required to achieve a 3%= p E(MeV) energy resolution with very low radioactive background, which is a big challenge to the detector design. In order to ensure the detector performance can meet the physics requirements, reliable detector simulation is necessary to provide useful information for the detector design. A simulation study of natural radioactivity backgrounds in the JUNO central detector has been performed to guide the detector design and set requirements for the radio-purity of the detector materials. The accidental background induced by natural radioactivity in the JUNO central detector is 1.1/day. The result is satisfled for the experiment.

Physics potential of searching for

In past decades numerous efforts were made searching for neutrinoless double-beta decay (

0\nu\beta\beta

0\nu\beta\beta

decays in JUNO

) process, aiming to establish whether neutrinos are their own antiparticles (Majorana neutrinos), yet no