169 research outputs found
Advanced code-division multiplexers for superconducting detector arrays
Multiplexers based on the modulation of superconducting quantum interference
devices are now regularly used in multi-kilopixel arrays of superconducting
detectors for astrophysics, cosmology, and materials analysis. Over the next
decade, much larger arrays will be needed. These larger arrays require new
modulation techniques and compact multiplexer elements that fit within each
pixel. We present a new in-focal-plane code-division multiplexer that provides
multiplexing elements with the required scalability. This code-division
multiplexer uses compact lithographic modulation elements that simultaneously
multiplex both signal outputs and superconducting transition-edge sensor (TES)
detector bias voltages. It eliminates the shunt resistor used to voltage bias
TES detectors, greatly reduces power dissipation, allows different dc bias
voltages for each TES, and makes all elements sufficiently compact to fit
inside the detector pixel area. These in-focal-plane code-division multiplexers
can be combined with multi-gigahertz readout based on superconducting
microresonators to scale to even larger arrays.Comment: 8 pages, 3 figures, presented at the 14th International Workshop on
Low Temperature Detectors, Heidelberg University, August 1-5, 2011,
proceedings to be published in the Journal of Low Temperature Physic
A microscopic approach to the response of He -He mixtures
Correlated Basis Function perturbation theory is used to evaluate the zero
temperature response of He-He mixtures for inelastic
neutron scattering, at momentum transfers ranging from to . We adopt a Jastrow correlated ground state and a basis of correlated
particle-hole and phonon states. We insert correlated one particle-one hole and
one-phonon states to compute the second order response. The decay of the
one-phonon states into two-phonon states is accounted for in boson-boson
approximation. The full response is splitted into three partial components
, each of them showing a particle-hole bump and a
one phonon, delta shaped peak, which stays separated from the multiphonon
background. The cross term results to be of comparable
importance to in the particle-hole sector and to
in the phonon one. Once the one-phonon peak has been
convoluted with the experimental broadening, the computed scattering function
is in semiquantitative agreement with recent experimental measurements.Comment: 26 pages, RevTex 3.0, 8 figures available upon reques
Geology, geochemistry and earthquake history of Lō`ihi Seamount, Hawai`i
Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Chemie der Erde - Geochemistry 66 (2006): 81-108, doi:10.1016/j.chemer.2005.09.002.A half century of investigations are summarized here on the youngest Hawaiian volcano, Lō`ihi Seamount. It was discovered in 1952 following an earthquake swarm. Surveying in 1954 determined it has an elongate shape, which is the meaning of its Hawaiian name. Lō`ihi was
mostly forgotten until two earthquake swarms in the 1970’s led to a dredging expedition in 1978, which recovered young lavas. This led to numerous expeditions to investigate the geology, geophysics, and geochemistry of this active volcano. Geophysical monitoring, including a realtime
submarine observatory that continuously monitored Lō`ihi’s seismic activity for three
months, captured some of the volcano’s earthquake swarms. The 1996 swarm, the largest
recorded in Hawai`i, was preceded by at least one eruption and accompanied by the formation of
a ~300-m deep pit crater, renewing interest in this submarine volcano. Seismic and petrologic
data indicate that magma was stored in a ~8-9 km deep reservoir prior to the 1996 eruption.
Studies on Lō`ihi have altered conceptual models for the growth of Hawaiian and other
oceanic island volcanoes and led to a refined understanding of mantle plumes. Petrologic and
geochemical studies of Lō`ihi lavas showed that the volcano taps a relatively primitive part of
the Hawaiian plume, producing a wide range of magma compositions. These compositions have
become progressively more silica-saturated with time reflecting higher degrees of partial melting
as the volcano drifts towards the center of the hotspot. Seismic and bathymetric data have
highlighted the importance of landsliding in the early formation of an ocean island volcano.
Lō`ihi’s internal structure and eruptive behavior, however, cannot be fully understood without
installing monitoring equipment directly on the volcano.
The presence of hydrothermal activity at Lō`ihi was initially proposed based on nontronite
deposits on dredged samples that indicated elevated temperatures (31oC), and on the detection of water temperature, methane and 3He anomalies, and clumps of benthic micro-organisms in the
water column over the volcano in 1982. Submersible observations in 1987 confirmed a low
temperature system (15-30oC) prior to the 1996 formation of Pele’s Pit. The sulfide mineral
assemblage (wurtzite, pyrrhotite, and chalcopyrite) deposited after the pit crater collapsed are
consistent with hydrothermal fluids >250oC. Vent temperatures have decreased to ~60oC during
the 2004 dive season indicating the current phase of hydrothermal activity may be waning.This work
was supported by a NSF grant to M. Garcia (OCE 97-29894)
The Atacama Cosmology Telescope: A Catalog of >4000 Sunyaev–Zel’dovich Galaxy Clusters
We present a catalog of 4195 optically confirmed Sunyaev–Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 × 1014 M⊙, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2farcm4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr
A resonant-term-based model including a nascent disk, precession, and oblateness: application to GJ 876
Investigations of two resonant planets orbiting a star or two resonant
satellites orbiting a planet often rely on a few resonant and secular terms in
order to obtain a representative quantitative description of the system's
dynamical evolution. We present a semianalytic model which traces the orbital
evolution of any two resonant bodies in a first- through fourth-order
eccentricity or inclination-based resonance dominated by the resonant and
secular arguments of the user's choosing. By considering the variation of
libration width with different orbital parameters, we identify regions of phase
space which give rise to different resonant ''depths,'' and propose methods to
model libration profiles. We apply the model to the GJ 876 extrasolar planetary
system, quantify the relative importance of the relevant resonant and secular
contributions, and thereby assess the goodness of the common approximation of
representing the system by just the presumably dominant terms. We highlight the
danger in using ''order'' as the metric for accuracy in the orbital solution by
revealing the unnatural libration centers produced by the second-order, but not
first-order, solution, and by demonstrating that the true orbital solution lies
somewhere ''in-between'' the third- and fourth-order solutions. We also present
formulas used to incorporate perturbations from central-body oblateness and
precession, and a protoplanetary or protosatellite thin disk with gaps, into a
resonant system. We quantify these contributions to the GJ 876 system, and
thereby highlight the conditions which must exist for multi-planet exosystems
to be significantly influenced by such factors. We find that massive enough
disks may convert resonant libration into circulation; such disk-induced
signatures may provide constraints for future studies of exoplanet systems.Comment: 39 pages of body text, 21 figures, 5 tables, 1 appendix, accepted for
publication in Celestial Mechanics and Dynamical Astronom
Measurement of the splashback feature around SZ-selected Galaxy clusters with DES, SPT, and ACT
We present a detection of the splashback feature around galaxy clusters selected using the Sunyaev–Zel’dovich (SZ) signal. Recent measurements of the splashback feature around optically selected galaxy clusters have found that the splashback radius, rsp, is smaller than predicted by N-body simulations. A possible explanation for this discrepancy is that rsp inferred from the observed radial distribution of galaxies is affected by selection effects related to the optical cluster-finding algorithms. We test this possibility by measuring the splashback feature in clusters selected via the SZ effect in data from the South Pole Telescope SZ survey and the Atacama Cosmology Telescope Polarimeter survey. The measurement is accomplished by correlating these cluster samples with galaxies detected in the Dark Energy Survey Year 3 data. The SZ observable used to select clusters in this analysis is expected to have a tighter correlation with halo mass and to be more immune to projection effects and aperture-induced biases, potentially ameliorating causes of systematic error for optically selected clusters. We find that the measured rsp for SZ-selected clusters is consistent with the expectations from simulations, although the small number of SZ-selected clusters makes a precise comparison difficult. In agreement with previous work, when using optically selected redMaPPer clusters with similar mass and redshift distributions, rsp is ∼2σ smaller than in the simulations. These results motivate detailed investigations of selection biases in optically selected cluster catalogues and exploration of the splashback feature around larger samples of SZ-selected clusters. Additionally, we investigate trends in the galaxy profile and splashback feature as a function of galaxy colour, finding that blue galaxies have profiles close to a power law with no discernible splashback feature, which is consistent with them being on their first infall into the cluster
The Atacama Cosmology Telescope: The Two-season ACTPol Sunyaev-Zel'dovich Effect Selected Cluster Catalog
Large scale structure and cosmolog
Search for the doubly heavy baryon decaying to
A first search for the
decay is performed by the LHCb experiment with a data sample of proton-proton
collisions, corresponding to an integrated luminosity of
recorded at centre-of-mass energies of 7, 8, and . Two peaking structures are seen with a local (global) significance of
and standard deviations at masses of
and , respectively. Upper limits are set on the baryon
production cross-section times the branching fraction relative to that of the
decay at centre-of-mass energies of 8 and
, in the and in the
rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to
, respectively. Upper limits are presented
as a function of the mass and lifetime.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-005.html (LHCb
public pages
Strong detection of the CMB lensing and galaxy weak lensing cross-correlation from ACT-DR4, Planck Legacy, and KiDS-1000
Large scale structure and cosmolog
Strong detection of the CMB lensing and galaxy weak lensing cross-correlation from ACT-DR4, Planck Legacy, and KiDS-1000
Large scale structure and cosmolog
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