118598186
The Daya Bay antineutrino detector filling system and liquid mass measurement
The Daya Bay Reactor Neutrino Experiment has measured the neutrino mixing angle ?13 to world-leading precision. The experiment uses eight antineutrino detectors filled with 20-tons of gadolinium-doped liquid scintillator to detect antineutrinos emitted from the Daya Bay nuclear power plant through the inverse beta decay reaction. The precision measurement of sin22?13 relies on the relative antineutrino interaction rates between detectors at near (400 m) and far (roughly 1.8 km) distances from the nuclear reactors. The measured interaction rate in each detector is directly proportional to the number of protons in the liquid scintillator target. A precision detector filling system was developed to simultaneously fill the three liquid zones of the antineutrino detectors and measure the relative target mass between detectors to < 0.02%. This paper describes the design, operation, and performance of the system and the resulting precision measurement of the detectors' target liquid masses.
117196215
Studies of non-standard effects in atmospheric neutrino oscillations of Super-Kamiokande
118791439
Reactor Neutrino Experiments: $\theta_{13}$ and Beyond
We review the current-generation short-baseline reactor neutrino experiments that have firmly established the third neutrino mixing angle $\theta_{13}$ to be non-zero. The relative large value of $\theta_{13}$ (around 9$^\circ$) has opened many new and exciting opportunities for future neutrino experiments. Daya Bay experiment with the first measurement of $\Delta m^2_{ee}$ is aiming for a precision measurement of this atmospheric mass-squared splitting with a comparable precision as $\Delta m^2_{\mu\mu}$ from accelerator muon neutrino experiments. JUNO, a next-generation reactor neutrino experiment, is targeting to determine the neutrino mass hierarchy with medium baselines ($\sim$50 km). Beside these {\color{black} opportunities enabled by the large $\theta_{13}$}, the current-generation (Daya Bay, Double Chooz, and RENO) and the next-generation (JUNO, RENO-50, and PROSPECT) reactor experiments, with their unprecedented statistics, are also leading the precision era of the 3-flavor neutrino oscillation physics as well as constraining new physics beyond the neutrino Standard Model.
120923082
Constraints on sterile neutrinos using Super-Kamiokande I atmospheric neutrino data
119115457
Light dark matter in NMSSM and implication on Higgs phenomenology
For the experimental search of neutralino dark matter, it is important to know its allowed mass and scattering cross section with the nucleon. In order to figure out how light a neutralino dark matter can be predicted in low energy supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal supersymmetric model), assuming all the relevant soft mass parameters to be below TeV scale. We find that in the parameter space allowed by current experiments the neutralino dark matter can be as light as a few GeV and its scattering rate off the nucleon can reach the sensitivity of XENON100 and CoGeNT. As a result, a sizable parameter space is excluded by the current XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be explained). The future 6000 kg-days exposure of XENON100 will further explore (but cannot completely cover) the remained parameter space. Moreover, we find that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson must be present to satisfy the measured dark matter relic density. Consequently, the SM-like Higgs boson h(SM) may decay predominantly into a pair of light Higgs bosons or a pair of neutralinos so that the conventional decays like h(SM) -> gamma gamma is much suppressed. (C) 2011 Elsevier B.V. All rights reserved.
29083543
THE DEEP SWIRE FIELD. IV. FIRST PROPERTIES OF THE SUB-mJy GALAXY POPULATION: REDSHIFT DISTRIBUTION, AGN ACTIVITY, AND STAR FORMATION
We present a study of a 20 cm selected sample in the Deep Spitzer Wide-area InfraRed Extragalactic Legacy Survey Very Large Array Field, reaching a 5σ limiting flux density at the image center of S_(1.4 GHz) ~ 13.5 μJy. In a 0.6 × 0.6 deg^2 field, we are able to assign an optical/IR counterpart to 97% of the radio sources. Up to 11 passbands from the NUV to 4.5 μm are then used to sample the spectral energy distribution (SED) of these counterparts in order to investigate the nature of the host galaxies. By means of an SED template library and stellar population synthesis models, we estimate photometric redshifts, stellar masses, and stellar population properties, dividing the sample into three sub-classes of quiescent, intermediate, and star-forming galaxies. We focus on the radio sample in the redshift range 0.3 < z < 1.3 where we estimate to have a redshift completeness higher than 90% and study the properties and redshift evolution of these sub-populations. We find that, as expected, the relative contributions of active galactic nuclei (AGNs) and star-forming galaxies to the μJy population depend on the flux density limit of the sample. At all flux levels, a significant population of "green-valley" galaxies is observed. While the actual nature of these sources is not definitely understood, the results of this work may suggest that a significant fraction of faint radio sources might be composite (and possibly transition) objects, thus a simple "AGN versus star-forming" classification might not be appropriate to fully understand what faint radio populations really are.
199675659
The Resolved Near-Infrared Extragalactic Background
73576245
Submillimeter Sources behind the Massive Lensing Clusters A370 and A2390
We report 850 μm Submillimeter Array (SMA) observations of four gravitationally lensed submillimeter galaxies (SMGs), A370-2, A2390-1, A2390-3, and A2390-4, which were originally discovered with the Submillimeter Common-User Bolometer Array (SCUBA). Our SMA detection of A370-2 with a submillimeter flux of 7.95 ± 0.60 mJy unambiguously identifies the counterparts to this source at optical and radio wavelengths. A2390-1 is an ultraluminous infrared galaxy with a submillimeter flux of 5.55 ± 0.92 mJy and a redshift of 1.8 ± 0.2 computed from submillimeter/radio flux ratio analysis. We resolve A2390-3 into two components, A2390-3a and A2390-3b, with fluxes of 3.15 ± 0.63 mJy and 1.92 ± 0.60 mJy, respectively. The structure of the system could be consistent with morphological distortion by gravitational lensing. The lack of counterparts in the optical and infrared indicates a heavily dust-enshrouded nature, and a non-detection in the radio implies that these two sources probably lie at z > 4.7, which would make them among the most distant SMGs known to date. Our non-detection of A2390-4 suggests either that there are multiple fainter submillimeter sources within the SCUBA beam or that the SCUBA detection may have been false. Our precise positions allow us to determine accurate amplifications and fluxes for all of our detected sources. Our new results give a shallower power-law fit (–1.10) to the faint-end 850 μm cumulative number counts than previous work. We emphasize the need for high-resolution observations of single dish detected SMGs in order to measure accurately the faint end of the 850 μm counts.
118306564
SMA OBSERVATIONS ON FAINT SUBMILLIMETER GALAXIES WITH S 850 < 2 mJy: ULTRA DUSTY LOW-LUMINOSITY GALAXIES AT HIGH REDSHIFT
We obtained Submillimeter Array (SMA) observations of eight faint (intrinsic 850 μm fluxes < 2 mJy) submillimeter galaxies (SMGs) discovered in SCUBA images of the massive lensing cluster fields A370, A2390, and A1689 and detected five. In total, we obtain five SMA detections, all of which have de-lensed fluxes <1 mJy with estimated total infrared luminosities 10{sup 10}-10{sup 12} L {sub ☉}, comparable to luminous infrared galaxies and normal star-forming galaxies. Based on the latest number counts, these galaxies contribute ∼70% of the 850 μm extragalactic background light and represent the dominant star-forming galaxy population in the dusty universe. However, only 40{sub −16}{sup +30}% of our faint SMGs would be detected in deep optical or near-infrared surveys, which suggests many of these sources are at high redshifts (z ≳ 3) or extremely dusty, and they are not included in current star formation history estimates.