2,555 research outputs found
Impact of Point Spread Function Higher Moments Error on Weak Gravitational Lensing II: A Comprehensive Study
Weak gravitational lensing, or weak lensing, is one of the most powerful
probes for dark matter and dark energy science, although it faces increasing
challenges in controlling systematic uncertainties as \edit{the statistical
errors become smaller}. The Point Spread Function (PSF) needs to be precisely
modeled to avoid systematic error on the weak lensing measurements. The weak
lensing biases induced by errors in the PSF model second moments, i.e., its
size and shape, are well-studied. However, Zhang et al. (2021) showed that
errors in the higher moments of the PSF may also be a significant source of
systematics for upcoming weak lensing surveys. Therefore, the goal of this work
is to comprehensively investigate the modeling quality of PSF moments from the
to order, and estimate their impact on
cosmological parameter inference. We propagate the \textsc{PSFEx} higher
moments modeling error in the HSC survey dataset to the weak lensing
\edit{shear-shear correlation functions} and their cosmological analyses. We
find that the overall multiplicative shear bias associated with errors in PSF
higher moments can cause a shift on the cosmological
parameters for LSST Y10. PSF higher moment errors also cause additive biases in
the weak lensing shear, which, if not accounted for in the cosmological
parameter analysis, can induce cosmological parameter biases comparable to
their uncertainties for LSST Y10. We compare the \textsc{PSFEx} model
with PSF in Full FOV (\textsc{Piff}), and find similar performance in modeling
the PSF higher moments. We conclude that PSF higher moment errors of the future
PSF models should be reduced from those in current methods to avoid a need to
explicitly model these effects in the weak lensing analysis.Comment: 24 pages, 17 figures, 3 tables; Submitted to MNRAS; Comments welcome
Periodic Astrometric Signal Recovery Through Convolutional Autoencoders
Astrometric detection involves precise measurements of stellar positions, and it is widely regarded as the leading concept presently ready to find Earth-mass planets in temperate orbits around nearby sun-like stars. The TOLIMAN space telescope [39] is a low-cost, agile mission concept dedicated to narrow-angle astrometric monitoring of bright binary stars. In particular the mission will be optimised to search for habitable-zone planets around {\}{\$}{\backslash}alpha {\$}{\$}\alpha$ Centauri AB. If the separation between these two stars can be monitored with sufficient precision, tiny perturbations due to the gravitational tug from an unseen planet can be witnessed and, given the configuration of the optical system, the scale of the shifts in the image plane are about one-millionth of a pixel. Image registration at this level of precision has never been demonstrated (to our knowledge) in any setting within science. In this paper, we demonstrate that a Deep Convolutional Auto-Encoder is able to retrieve such a signal from simplified simulations of the TOLIMAN data and we present the full experimental pipeline to recreate out experiments from the simulations to the signal analysis. In future works, all the more realistic sources of noise and systematic effects present in the real-world system will be injected into the simulations
Periodic Astrometric Signal Recovery through Convolutional Autoencoders
Astrometric detection involves a precise measurement of stellar positions,
and is widely regarded as the leading concept presently ready to find
earth-mass planets in temperate orbits around nearby sun-like stars. The
TOLIMAN space telescope[39] is a low-cost, agile mission concept dedicated to
narrow-angle astrometric monitoring of bright binary stars. In particular the
mission will be optimised to search for habitable-zone planets around Alpha
Centauri AB. If the separation between these two stars can be monitored with
sufficient precision, tiny perturbations due to the gravitational tug from an
unseen planet can be witnessed and, given the configuration of the optical
system, the scale of the shifts in the image plane are about one millionth of a
pixel. Image registration at this level of precision has never been
demonstrated (to our knowledge) in any setting within science. In this paper we
demonstrate that a Deep Convolutional Auto-Encoder is able to retrieve such a
signal from simplified simulations of the TOLIMAN data and we present the full
experimental pipeline to recreate out experiments from the simulations to the
signal analysis. In future works, all the more realistic sources of noise and
systematic effects present in the real-world system will be injected into the
simulations.Comment: Preprint version of the manuscript to appear in the Volume
"Intelligent Astrophysics" of the series "Emergence, Complexity and
Computation", Book eds. I. Zelinka, D. Baron, M. Brescia, Springer Nature
Switzerland, ISSN: 2194-728
Smart Tungsten-based Alloys for a First Wall of DEMO
During an accident with loss-of-coolant and air ingress in DEMO, the temperature of tungsten first wall cladding may exceed 1000 °C and remain for months leading to tungsten oxidation. The radioactive tungsten oxide can be mobilized to the environment at rates of 10–150 kg per hour. Smart tungsten-based alloys are under development to address this issue. Alloys are aimed to function as pure tungsten during regular plasma operation of DEMO. During an accident, alloying elements will create a protective layer, suppressing release of W oxide. Bulk smart alloys were developed by using mechanical alloying and field-assisted sintering technology. The mechanical alloying process was optimized leading to an increased powder production by at least 40 %. Smart alloys and tungsten were tested under a variety of DEMO-relevant plasma conditions. Both materials demonstrated similar sputtering resistance to deuterium plasma. Under accident conditions, alloys feature a 40-fold reduction of W release compared to that of pure tungsten.</p
Genetic Determinants of Circulating Sphingolipid Concentrations in European Populations
Sphingolipids have essential roles as structural components of cell membranes and in cell signalling, and disruption of their metabolism causes several diseases, with diverse neurological, psychiatric, and metabolic consequences. Increasingly, variants within a few of the genes that encode enzymes involved in sphingolipid metabolism are being associated with complex disease phenotypes. Direct experimental evidence supports a role of specific sphingolipid species in several common complex chronic disease processes including atherosclerotic plaque formation, myocardial infarction (MI), cardiomyopathy, pancreatic beta-cell failure, insulin resistance, and type 2 diabetes mellitus. Therefore, sphingolipids represent novel and important intermediate phenotypes for genetic analysis, yet little is known about the major genetic variants that influence their circulating levels in the general population. We performed a genome-wide association study (GWAS) between 318,237 single-nucleotide polymorphisms (SNPs) and levels of circulating sphingomyelin (SM), dihydrosphingomyelin (Dih-SM), ceramide (Cer), and glucosylceramide (GluCer) single lipid species (33 traits); and 43 matched metabolite ratios measured in 4,400 subjects from five diverse European populations. Associated variants (32) in five genomic regions were identified with genome-wide significant corrected p-values ranging down to 9.08 x 10(-66). The strongest associations were observed in or near 7 genes functionally involved in ceramide biosynthesis and trafficking: SPTLC3, LASS4, SGPP1, ATP10D, and FADS1-3. Variants in 3 loci (ATP10D, FADS3, and SPTLC3) associate with MI in a series of three German MI studies. An additional 70 variants across 23 candidate genes involved in sphingolipid-metabolizing pathways also demonstrate association (p = 10(-4) or less). Circulating concentrations of several key components in sphingolipid metabolism are thus under strong genetic control, and variants in these loci can be tested for a role in the development of common cardiovascular, metabolic, neurological, and psychiatric diseases
Measurement of the Branching Fraction for B- --> D0 K*-
We present a measurement of the branching fraction for the decay B- --> D0
K*- using a sample of approximately 86 million BBbar pairs collected by the
BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is
detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the
K*- through its decay to K0S pi-. We measure the branching fraction to be
B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid
Communications
Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction
We present evidence for the flavor-changing neutral current decay and a measurement of the branching fraction for the related
process , where is either an or
pair. These decays are highly suppressed in the Standard Model,
and they are sensitive to contributions from new particles in the intermediate
state. The data sample comprises
decays collected with the Babar detector at the PEP-II storage ring.
Averaging over isospin and lepton flavor, we obtain the branching
fractions and , where the
uncertainties are statistical and systematic, respectively. The significance of
the signal is over , while for it is .Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let
Standalone vertex finding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson
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