257 research outputs found
Guiding slow polar molecules with a charged wire
We demonstrate experimentally the guiding of cold and slow ND3 molecules
along a thin charged wire over a distance of ~0.34 m through an entire
molecular beam apparatus. Trajectory simulations confirm that both linear and
quadratic high-field-seeking Stark states can be efficiently guided from the
beam source up to the detector. A density enhancement up to a factor 7 is
reached for decelerated beams with velocities ranging down to ~50 m/s generated
by the rotating nozzle technique
The new generation CMB B-mode polarization experiment: POLARBEAR
We describe the Cosmic Microwave Background (CMB) polarization experiment
called Polarbear. This experiment will use the dedicated Huan Tran Telescope
equipped with a powerful 1,200-bolometer array receiver to map the CMB
polarization with unprecedented accuracy. We summarize the experiment, its
goals, and current status
Ultra High Energy Cosmology with POLARBEAR
Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
Radiation hardness studies of a 130 nm Silicon Germanium BiCMOS technology with a dedicated ASIC
We present the radiation hardness studies on the bipolar devices of the 130 nm 8WL Silicon Germanium (SiGe) BiCMOS technology from IBM. This technology has been proposed as one of the candidates for the Front-End (FE) readout chip of the upgraded Inner Detector (ID) and the Liquid Argon Calorimeter (LAr) of the ATLAS Upgrade experiment. After neutron irradiations, devices remain at acceptable performances at the maximum radiation levels expected in the Si tracker and LAr calorimeter
Mass Calibration and Cosmological Analysis of the SPT-SZ Galaxy Cluster Sample Using Velocity Dispersion and X-ray Measurements
We present a velocity dispersion-based mass calibration of the South Pole
Telescope Sunyaev-Zel'dovich effect survey (SPT-SZ) galaxy cluster sample.
Using a homogeneously selected sample of 100 cluster candidates from 720 deg2
of the survey along with 63 velocity dispersion () and 16 X-ray Yx
measurements of sample clusters, we simultaneously calibrate the
mass-observable relation and constrain cosmological parameters. The
calibrations using and Yx are consistent at the level,
with the calibration preferring ~16% higher masses. We use the full
cluster dataset to measure . The
SPT cluster abundance is lower than preferred by either the WMAP9 or
Planck+WMAP9 polarization (WP) data, but assuming the sum of the neutrino
masses is eV, we find the datasets to be consistent at the
1.0 level for WMAP9 and 1.5 for Planck+WP. Allowing for larger
further reconciles the results. When we combine the cluster and
Planck+WP datasets with BAO and SNIa, the preferred cluster masses are
higher than the Yx calibration and higher than the
calibration. Given the scale of these shifts (~44% and ~23% in mass,
respectively), we execute a goodness of fit test; it reveals no tension,
indicating that the best-fit model provides an adequate description of the
data. Using the multi-probe dataset, we measure and
. Within a CDM model we find eV. We present a consistency test of the cosmic growth rate.
Allowing both the growth index and the dark energy equation of state
parameter to vary, we find and ,
demonstrating that the expansion and the growth histories are consistent with a
LCDM model ().Comment: Accepted by ApJ (v2 is accepted version); 17 pages, 6 figure
Analysis of Sunyaev-Zel'dovich Effect Mass-Observable Relations using South Pole Telescope Observations of an X-ray Selected Sample of Low Mass Galaxy Clusters and Groups
(Abridged) We use 95, 150, and 220GHz observations from the SPT to examine
the SZE signatures of a sample of 46 X-ray selected groups and clusters drawn
from ~6 deg^2 of the XMM-BCS. These systems extend to redshift z=1.02, have
characteristic masses ~3x lower than clusters detected directly in the SPT data
and probe the SZE signal to the lowest X-ray luminosities (>10^42 erg s^-1)
yet.
We develop an analysis tool that combines the SZE information for the full
ensemble of X-ray-selected clusters. Using X-ray luminosity as a mass proxy, we
extract selection-bias corrected constraints on the SZE significance- and
Y_500-mass relations. The SZE significance- mass relation is in good agreement
with an extrapolation of the relation obtained from high mass clusters.
However, the fit to the Y_500-mass relation at low masses, while in good
agreement with the extrapolation from high mass SPT clusters, is in tension at
2.8 sigma with the constraints from the Planck sample. We examine the tension
with the Planck relation, discussing sample differences and biases that could
contribute.
We also present an analysis of the radio galaxy point source population in
this ensemble of X-ray selected systems. We find 18 of our systems have 843 MHz
SUMSS sources within 2 arcmin of the X-ray centre, and three of these are also
detected at significance >4 by SPT. Of these three, two are associated with the
group brightest cluster galaxies, and the third is likely an unassociated
quasar candidate. We examine the impact of these point sources on our SZE
scaling relation analyses and find no evidence of biases. We also examine the
impact of dusty galaxies using constraints from the 220 GHz data. The stacked
sample provides 2.8 significant evidence of dusty galaxy flux, which
would correspond to an average underestimate of the SPT Y_500 signal that is
(17+-9) per cent in this sample of low mass systems.Comment: 15 pages, 7 figure
Cosmological Constraints from Galaxy Clusters in the 2500 square-degree SPT-SZ Survey
(abridged) We present cosmological constraints obtained from galaxy clusters
identified by their Sunyaev-Zel'dovich effect signature in the 2500 square
degree South Pole Telescope Sunyaev Zel'dovich survey. We consider the 377
cluster candidates identified at z>0.25 with a detection significance greater
than five, corresponding to the 95% purity threshold for the survey. We compute
constraints on cosmological models using the measured cluster abundance as a
function of mass and redshift. We include additional constraints from
multi-wavelength observations, including Chandra X-ray data for 82 clusters and
a weak lensing-based prior on the normalization of the mass-observable scaling
relations. Assuming a LCDM cosmology, where the species-summed neutrino mass
has the minimum allowed value (mnu = 0.06 eV) from neutrino oscillation
experiments, we combine the cluster data with a prior on H0 and find sigma_8 =
0.797+-0.031 and Omega_m = 0.289+-0.042, with the parameter combination
sigma_8(Omega_m/0.27)^0.3 = 0.784+-0.039. These results are in good agreement
with constraints from the CMB from SPT, WMAP, and Planck, as well as with
constraints from other cluster datasets. Adding mnu as a free parameter, we
find mnu = 0.14+-0.08 eV when combining the SPT cluster data with Planck CMB
data and BAO data, consistent with the minimum allowed value. Finally, we
consider a cosmology where mnu and N_eff are fixed to the LCDM values, but the
dark energy equation of state parameter w is free. Using the SPT cluster data
in combination with an H0 prior, we measure w = -1.28+-0.31, a constraint
consistent with the LCDM cosmological model and derived from the combination of
growth of structure and geometry. When combined with primarily geometrical
constraints from Planck CMB, H0, BAO and SNe, adding the SPT cluster data
improves the w constraint from the geometrical data alone by 14%, to w =
-1.023+-0.042
Constraints on the CMB Temperature Evolution using Multi-Band Measurements of the Sunyaev Zel'dovich Effect with the South Pole Telescope
The adiabatic evolution of the temperature of the cosmic microwave background
(CMB) is a key prediction of standard cosmology. We study deviations from the
expected adiabatic evolution of the CMB temperature of the form using measurements of the spectrum of the Sunyaev
Zel'dovich Effect with the South Pole Telescope (SPT). We present a method for
using the ratio of the Sunyaev Zel'dovich signal measured at 95 and 150 GHz in
the SPT data to constrain the temperature of the CMB. We demonstrate that this
approach provides unbiased results using mock observations of clusters from a
new set of hydrodynamical simulations. We apply this method to a sample of 158
SPT-selected clusters, spanning the redshift range , and
measure , consistent with the standard model
prediction of . In combination with other published results, we
constrain , an improvement of over
published constraints. This measurement also provides a strong constraint on
the effective equation of state in models of decaying dark energy
.Comment: Submitted to MNRAS Letter
Just compensation? The price of death and injury after the Rana Plaza garment factory collapse
The 2013 collapse of the Rana Plaza factory building in Dhaka, Bangladesh was the most deadly disaster in garment manufacturing history, with at least 1,134 people killed and hundreds injured. In 2015, injured workers and the families of those killed received compensation from global apparel brands through a $30 million voluntary initiative known as the Rana Plaza Arrangement. Overseen by the International Labour Organization (ILO), the Rana Plaza Arrangement awarded payments to survivors using a pricing formula developed by a diverse team of âstakeholdersâ that included labour groups, multinational apparel companies, representatives of the Bangladesh government and local employers, and ILO actuaries. This article draws from anthropological scholarship on the âjust priceâ to explore how a formula for pricing death and injury became both the means and form of a fragile political settlement in the wake of a shocking and widely publicised industrial disaster. By unpacking the complicated âethics of a formulaâ (Ballestero 2015), I demonstrate how the project of creating a just price involves not two sets of values (ethical and financial) but rather multiple, competing values. This article argues for recognition of the persistence and power of these competing values, showing how they variously strengthen and undermine the claim that justice was served by the Rana Plaza Arrangement. This analysis reveals the deficiencies of counterposing âmoralityâ and âeconomyâ in the study of price by reflecting upon all elements of price as situated within political economy and history
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