118448597
NEW 145-MHZ SOURCE MEASUREMENTS BY PAPER IN THE SOUTHERN SKY
We present observations from the Precision Array for Probing the Epoch of Reionization (PAPER) in South Africa, observed in May and September 2010. Using two nights of drift scanning with PAPER’s 60 ◦ FWHM beam we have made a map covering the entire sky below +10 degrees declination with an effective center frequency of 145 MHz, a 70-MHz bandwidth, and a resolution of 26 ′ . A 4800 square-degree region of this large map with the lowest Galactic emission reaches an RMS of 0.7 Jy. We establish an absolute flux scale using sources from the 160-MHz Culgoora catalog. Using the 408-MHz Molonglo Reference Catalog (MRC) as a finding survey, we identify counterparts to 480 sources in our maps, and compare our fluxes to the MRC and to 332 sources in the Culgoora catalog. For both catalogs, the ratio of PAPER to catalog flux averages to 1, with a standard deviation of 50%. This measured variation is consistent with comparisons between independent catalogs observed at different bands. The PAPER data represent new 145-MHz flux measurements for a large number of sources in the band expected to encompass cosmic reionization, and represents a significant step toward establishing a model for removing foregrounds to the reionization signal. Subject headings: dark ages, reionization, first stars — catalogs — instrumentation: interferometers
118516215
A TECHNIQUE FOR PRIMARY BEAM CALIBRATION OF DRIFT-SCANNING, WIDE-FIELD ANTENNA ELEMENTS
We present a new technique for calibrating the primary beam of a wide-field, drift-scanning antenna element. Drift-scan observing is not compatible with standard beam calibration routines, and the situation is further complicated by difficult-to-parameterize beam shapes and, at low frequencies, the sparsity of accurate source spectra to use as calibrators. We overcome these challenges by building up an interrelated network of source crossing points—locations where the primary beam is sampled by multiple sources. Using the single assumption that a beam has 180° rotational symmetry, we can achieve significant beam coverage with only a few tens of sources. The resulting network of crossing points allows us to solve for both a beam model and source flux densities referenced to a single calibrator source, circumventing the need for a large sample of well-characterized calibrators. We illustrate the method with actual and simulated observations from the Precision Array for Probing the Epoch of Reionization.
118343187
A Per-baseline, Delay-spectrum Technique for Accessing the 21 cm Cosmic Reionization Signature
A critical challenge in measuring the power spectrum of 21 cm emission from cosmic reionization is compensating for the frequency dependence of an interferometer's sampling pattern, which can cause smooth-spectrum foregrounds to appear unsmooth and degrade the separation between foregrounds and the target signal. In this paper, we present an approach to foreground removal that explicitly accounts for this frequency dependence. We apply the delay transformation introduced in Parsons and Backer to each baseline of an interferometer to concentrate smooth-spectrum foregrounds within the bounds of the maximum geometric delays physically realizable on that baseline. By focusing on delay modes that correspond to image-domain regions beyond the horizon, we show that it is possible to avoid the bulk of smooth-spectrum foregrounds. We map the point-spread function of delay modes to k-space, showing that delay modes that are uncorrupted by foregrounds also represent samples of the three-dimensional power spectrum, and can be used to constrain cosmic reionization. Because it uses only spectral smoothness to differentiate foregrounds from the targeted 21 cm signature, this per-baseline analysis approach relies on spectrally and spatially smooth instrumental responses for foreground removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering foregrounds, this techniquemore » substantially reduces the level of calibration previously thought necessary to detect 21 cm reionization. As a result, this approach places fewer constraints on antenna configuration within an array, and in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Under these assumptions, we demonstrate the potential for the Precision Array for Probing the Epoch of Reionization (PAPER) to detect 21 cm reionization at an amplitude of 10 mK{sup 2} near k {approx} 0.2 h Mpc{sup -1} with 132 dipoles in 7 months of observing.« less
3073653
Silicon detector dark matter results from the final exposure of CDMS II.
We report results of a search for weakly interacting massive particles (WIMPS) with the silicon detectors of the CDMS II experiment. This blind analysis of 140.2 kg day of data taken between July 2007 and September 2008 revealed three WIMP-candidate events with a surface-event background estimate of 0.41(-0.08)(+0.20)(stat)(-0.24)(+0.28)(syst). Other known backgrounds from neutrons and 206Pb are limited to <0.13 and <0.08 events at the 90% confidence level, respectively. The exposure of this analysis is equivalent to 23.4 kg day for a recoil energy range of 7-100 keV for a WIMP of mass 10  GeV/c2. The probability that the known backgrounds would produce three or more events in the signal region is 5.4%. A profile likelihood ratio test of the three events that includes the measured recoil energies gives a 0.19% probability for the known-background-only hypothesis when tested against the alternative WIMP+background hypothesis. The highest likelihood occurs for a WIMP mass of 8.6  GeV/c2 and WIMP-nucleon cross section of 1.9×10(-41)  cm2.
121546122
Central Hadron Calorimeter of UA1
Abstract An iron—scintillator sampling calorimeter is described, which measures hadronic energy in proton-antiproton interactions at the CERN 540 GeV SPS collider. Construction details are given of the instrumentation of the magnet pieces of the UA1 experiment and of the methods used to measure the calorimeter response and resolution. The system of lasers and quartz fibres, which allows long term monitoring of the calorimeter response, is also described.
118426859
SYSTEMATIC INVESTIGATIONS OF THE FREE FERMIONIC HETEROTIC STRING GAUGE GROUP STATISTICS: LAYER 1 RESULTS
Using software under development at Baylor University, we explicitly construct all layer 1 gauge, weakly coupled free fermionic heterotic string models up to order 22 in four large spacetime dimensions. The gauge models consist primarily of gauge content making a systematic construction process efficient. We present an overview of the model building procedure, redundancies in the process, methods used to reduce such redundancies and statistics regarding the occurrence of various combinations of gauge group factors and GUT groups. Statistics for both and models are presented.
16657381
Search for millicharged particles using optically levitated microspheres.
We report results from a search for stable particles with charge ≳10^{-5}e in bulk matter using levitated dielectric microspheres in high vacuum. No evidence for such particles was found in a total sample of 1.4 ng, providing an upper limit on the abundance per nucleon of 2.5×10^{-14} at the 95% confidence level for the material tested. These results provide the first direct search for single particles with charge ≲0.1e bound in macroscopic quantities of matter and demonstrate the ability to perform sensitive force measurements using optically levitated microspheres in vacuum.
119378198
Multiparticle States and the Hadron Spectrum on the Lattice
The Clebsch-Gordan decomposition is calculated for direct products of the irreducible representations of the cubic space group. These results are used to identify multiparticle states which appear in the hadron spectrum on the lattice. Consideration of the cubic space group indicates how combinations of both zero momentum and non-zero momentum multiparticle states contribute to the spectrum.