119244677
Target mass monitoring and instrumentation in the Daya Bay antineutrino detectors
The Daya Bay experiment measures sin 22θ13 using functionally identical antineutrino detectors located at distances of 300 to 2000 meters from the Daya Bay nuclear power complex. Each detector consists of three nested fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to overflow tanks on top of the detector to allow for thermal expansion of the liquid. Antineutrinos are detected through the inverse beta decay reaction on the proton-rich scintillator target. A precise and continuous measurement of the detector's central target mass is achieved by monitoring the the fluid level in the overflow tanks with cameras and ultrasonic and capacitive sensors. In addition, the monitoring system records detector temperature and levelness at multiple positions. This monitoring information allows the precise determination of the detectors' effective number of target protons during data taking. We present the design, calibration, installation and in-situ tests of the Daya Bay real-time antineutrino detector monitoring sensors and readout electronics.
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.
119144562
Quasifinite representations of classical Lie subalgebras of W (1+infinity)
We show that there are precisely two, up to conjugation, anti-involutions sigma_{\pm} of the algebra of differential operators on the circle preserving the principal gradation. We classify the irreducible quasifinite highest weight representations of the central extension \hat{D}^{\pm} of the Lie subalgebra of this algebra fixed by - sigma_{\pm}, and find the unitary ones. 
We realize them in terms of highest weight representations of the central extension of the Lie algebra of infinite matrices with finitely many non-zero diagonals over the truncated polynomial algebra C[u] / (u^{m+1}) and its classical Lie subalgebras of B, C and D types. Character formulas for positive primitive representations of \hat{D}^{\pm} (including all the unitary ones) are obtained. We also realize a class of primitive representations of \hat{D}^{\pm} in terms of free fields and establish a number of duality results between these primitive representations and finite-dimensional irreducible representations of finite-dimensional Lie groups and supergroups. We show that the vacuum module V_c of \hat{D}^+ carries a vertex algebra structure and establish a relationship between V_c for half-integral central charge c and W-algebras.
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.
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.
119180967
A KS AND IRAC SELECTION OF HIGH-REDSHIFT EXTREMELY RED OBJECTS*
In order to find the most extreme dust-hidden high-redshift galaxies, we select 196 extremely red objects in the K{sub S} and Infrared Array Camera (IRAC) bands (KIEROs, [K{sub s} - 4.5 {mu}m]{sub AB} > 1.6) in the 0.06 deg{sup 2} Great Observatories Origins Deep Surveys-North (GOODS-N) region. This selection avoids the Balmer breaks of galactic spectra at z 2 massive galaxies in rapid formation. Our results show that a large sample of dusty ultraluminous sources can be selected in this way and that a large fraction of high-redshift star formation is hidden by dust.« less
17191883
ULTRADEEP NEAR-INFRARED OBSERVATIONS OF GOODS 850-5*, **
GOODS 850-5 is a hyperluminous radio-faint submillimeter source in the Great Observatories Origins Deep Survey-North. Although it is generally agreed that GOODS 850-5 is at a high redshift, z 4, its exact redshift is unknown. While its stellar spectral energy distribution (SED) suggests z ~ 6, its radio/far-IR (FIR) SED suggests a lower redshift of z ~ 4. To better constrain its stellar SED and redshift, we carried out nano-Jansky sensitivity ultradeep near-IR (NIR) observations between 1.2 and 2.1 μm with the Hubble Space Telescope and the 8 m Subaru Telescope. Even with such great depths we did not detect GOODS 850-5, and the results show that it is an extremely curious source. Between the Ks and 3.6 μm bands, its spectral slope is greater than 3 times that of an extremely red object, and the flux ratio between the two bands is greater than 8 times that of Lyman breaks. It is quite challenging to explain this unusually red color without a Lyman break (which would imply z > 17). It requires a large amount (M ~ 1011.5 M ☉) of reddened old stars at z ~ 6, coexisting with an even more extinguished violent ~2400-4400 M ☉ yr–1 starburst, which does not have any associated detectable rest-frame UV radiation. We discuss the discrepancy between the NIR and radio/FIR photometric redshifts. We conclude that GOODS 850-5 is at least at z > 4 and is more likely at z 6. We describe the unusual properties of GOODS 850-5, including its SED and formation history, and we discuss the implications of such massive z > 6 galaxies.