5,607 research outputs found
Test Beam Results of Geometry Optimized Hybrid Pixel Detectors
The Multi-Chip-Module-Deposited (MCM-D) technique has been used to build
hybrid pixel detector assemblies. This paper summarises the results of an
analysis of data obtained in a test beam campaign at CERN. Here, single chip
hybrids made of ATLAS pixel prototype read-out electronics and special sensor
tiles were used. They were prepared by the Fraunhofer Institut fuer
Zuverlaessigkeit und Mikrointegration, IZM, Berlin, Germany. The sensors
feature an optimized sensor geometry called equal sized bricked. This design
enhances the spatial resolution for double hits in the long direction of the
sensor cells.Comment: Contribution to Proceedings of Pixel2005 Workshop, Bonn Germany 200
Qualification Procedures of the CMS Pixel Barrel Modules
The CMS pixel barrel system will consist of three layers built of about 800
modules. One module contains 66560 readout channels and the full pixel barrel
system about 48 million channels. It is mandatory to test each channel for
functionality, noise level, trimming mechanism, and bump bonding quality.
Different methods to determine the bump bonding yield with electrical
measurements have been developed. Measurements of several operational
parameters are also included in the qualification procedure. Among them are
pixel noise, gains and pedestals. Test and qualification procedures of the
pixel barrel modules are described and some results are presented.Comment: 7 Pages, 7 Figures. Contribution to Pixel 2005, September 5-8, 2005,
Bonn, Germna
Soft Fermi Surfaces and Breakdown of Fermi Liquid Behavior
Electron-electron interactions can induce Fermi surface deformations which
break the point-group symmetry of the lattice structure of the system. In the
vicinity of such a "Pomeranchuk instability" the Fermi surface is easily
deformed by anisotropic perturbations, and exhibits enhanced collective
fluctuations. We show that critical Fermi surface fluctuations near a d-wave
Pomeranchuk instability in two dimensions lead to large anisotropic decay rates
for single-particle excitations, which destroy Fermi liquid behavior over the
whole surface except at the Brillouin zone diagonal.Comment: 12 pages, 2 figures, revised version as publishe
Work Requirements in Public Housing: Impacts on Tenant Employment and Evictions
In recent years, many have debated adopting work requirements in the public housing program, and a limited number of public housing agencies (PHA) have implemented these policies through the flexibility provided by the Moving to Work program. One such agency—the Charlotte Housing Authority (CHA)—has implemented a work requirement across five (of 15) public housing developments that mandates households to work 15 hr weekly or face sanctions. This article evaluates this policy and presents the first empirical analysis on the outcomes of a work requirement on employment and evictions. We find that, following work requirement enforcement, the percentage of impacted households paying minimum rent (a proxy for nonemployment) decreased versus a comparison group. Analysis of additional data on both employment and hours worked indicates similar results regarding employment gains, but no increase in average hours worked. We find no evidence that work requirement sanctions increased evictions, and very modest evidence that enforcement increased the rate of positive move-outs such as moves to unsubsidized housing
Generalized modularity matrices
Various modularity matrices appeared in the recent literature on network
analysis and algebraic graph theory. Their purpose is to allow writing as
quadratic forms certain combinatorial functions appearing in the framework of
graph clustering problems. In this paper we put in evidence certain common
traits of various modularity matrices and shed light on their spectral
properties that are at the basis of various theoretical results and practical
spectral-type algorithms for community detection
CMS Barrel Pixel Detector Overview
The pixel detector is the innermost tracking device of the CMS experiment at
the LHC. It is built from two independent sub devices, the pixel barrel and the
end disks. The barrel consists of three concentric layers around the beam pipe
with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side
of the interaction point at 34.5 cm and 46.5 cm. This article gives an overview
of the pixel barrel detector, its mechanical support structure, electronics
components, services and its expected performance.Comment: Proceedings of Vertex06, 15th International Workshop on Vertex
Detector
Short-range correlations in asymmetric nuclear matter
The spectral function of protons in the asymmetric nuclear matter is
calculated in the self-consistent T-matrix approach. The spectral function per
proton increases with increasing asymmetry. This effect and the density
dependence of the spectral function partially explain the observed increase of
the spectral function with the mass number of the target nuclei in electron
scattering experiments
Pseudogap in fermionic density of states in the BCS-BEC crossover of atomic Fermi gases
We study pseudogap behaviors of ultracold Fermi gases in the BCS-BEC
crossover region. We calculate the density of states (DOS), as well as the
single-particle spectral weight, above the superfluid transition temperature
including pairing fluctuations within a -matrix approximation.
We find that DOS exhibits a pseudogap structure in the BCS-BEC crossover
region, which is most remarkable near the unitarity limit. We determine the
pseudogap temperature at which the pseudogap structure in DOS disappears.
We also introduce another temperature at which the BCS-like
double-peak structure disappears in the spectral weight. While one finds
in the BCS regime, becomes higher than in the
crossover and BEC regime. We also determine the pseudogap region in the phase
diagram in terms of temperature and pairing interaction.Comment: 6 pages, 4 figures, Proceedings of QFS 200
Instanton Contribution to the Proton and Neutron Electric Form Factors
We study the instanton contribution to the proton and neutron electric form
factors. Using the single instanton approximation, we perform the calculations
in a mixed time-momentum representation in order to obtain the form factors
directly in momentum space. We find good agreement with the experimentally
measured electric form factor of the proton. For the neutron, our result falls
short of the experimental data. We argue that this discrepancy is due to the
fact that we neglect the contribution of the sea quarks. We compare to lattice
calculations and a relativistic version of the quark-diquark model.Comment: 8 pages, 5 figures, updated references, to appear in Phys. Lett.
A Spectral Algorithm with Additive Clustering for the Recovery of Overlapping Communities in Networks
This paper presents a novel spectral algorithm with additive clustering
designed to identify overlapping communities in networks. The algorithm is
based on geometric properties of the spectrum of the expected adjacency matrix
in a random graph model that we call stochastic blockmodel with overlap (SBMO).
An adaptive version of the algorithm, that does not require the knowledge of
the number of hidden communities, is proved to be consistent under the SBMO
when the degrees in the graph are (slightly more than) logarithmic. The
algorithm is shown to perform well on simulated data and on real-world graphs
with known overlapping communities.Comment: Journal of Theoretical Computer Science (TCS), Elsevier, A Para\^itr
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