40,297 research outputs found
Higgs Boson Search Sensitivity in the Dilepton Decay Mode at and 10 TeV
Prospects for discovery of the standard model Higgs boson are examined at
center of mass energies of and TeV at the CERN Large Hadron Collider.
We perform a simulation of the signal and principal backgrounds for Higgs boson
production and decay in the dilepton mode, finding good agreement
with the ATLAS and CMS collaboration estimates of signal significance at 14 TeV
for Higgs boson masses near ~GeV. At the lower energy of ~TeV,
using the same analysis cuts as these collaborations, we compute expected
signal sensitivities of about standard deviations ('s) at ~GeV in the ATLAS case, and about 3.6~ in the CMS case for
~fb of integrated luminosity. Integrated luminosities of
8~ and 3~ are needed in the ATLAS case at and
~TeV, respectively, for level discovery. In the CMS case, the
numbers are 2~ and 1~ at and ~TeV. Our
different stated expectations for the two experiments arise from the more
restrictive analysis cuts in the CMS case. Recast as exclusion limits, our
results show that with of integrated luminosity at 7~TeV, the
LHC may be able to exclude values in the range 160 to 180~GeV provided no
signal is seen.Comment: 29 pages, 8 figures. New results on estimated discovery reach for
both CMS and ATLAS, as well as exclusion limits, along with comparisons with
Tevatron possibilities. References added
Preparation and in vitro characterization of scaffolds of poly(L-lactic acid) containing bioactive glass ceramic nanoparticles
Porous nanocomposite scaffolds of poly(L-lactic acid) (PLLA) containing different quantities of bioactive glass ceramic (BGC) nanoparticles
(SiO2:CaO:P2O5 ! 55:40:5 (mol)) were prepared by a thermally induced phase-separation method. Dioxane was used as the solvent
for PLLA. Introduction of less than 20 wt.% of BGC nanoparticles did not remarkably affect the porosity of PLLA foam. However,
as the BGC content increased to 30 wt.%, the porosity of the composite was observed to decrease rapidly. The compressive modulus of
the scaffolds increased from 5.5 to 8.0 MPa, while the compressive strength increased from 0.28 to 0.35 MPa as the BGC content
increased from 0 to 30 wt.%. The in vitro bioactivity and biodegradability of nanocomposites were investigated by incubation in simulated
body fluid (SBF) and phosphate-buffered saline, respectively. Scanning electron microscopy, energy dispersive X-ray spectroscopy,
Fourier transform infrared spectroscopy and X-ray diffraction were employed to monitor the surface variation of neat PLLA and PLLA/
BGC porous scaffolds during incubation. PLLA/(20 wt.%)BGC composite exhibited the best mineralization property in SBF, while the
PLLA/(10 wt.%)BGC composite showed the highest water absorption ability.This work was financially supported by FCT Grant for postdoctoral research (SFRH/BPD/25828/2005), and by the Projects POCTI/FIS/61621/2004 and PTDC/QUI/69263/2006. The authors also would like to acknowledge Dr. Aixue Liu, Changchun Institute of Applied Chemistry, for his help in characterization of composite material
Enhanced dielectric response by disordered nanoscale/mesoscopic insulators
Enhancement of the dielectric response of insulators by disorder is
theoretically proposed, where the quantum interference of electronic waves
through the nanoscale/mesoscopic system and its change due to external
perturbations control the polarization. In the disordered case with all the
states being localized, the resonant tunneling, which is topologically
protected, plays a crucial role, and enhances the dielectric response by a
factor 30~40 compared with the pure case. Realization of this idea with
accessible materials/structures is also discussed.Comment: 4 pages including 3 figures; minor revision; a high-resolution figure
available at http://appi.t.u-tokyo.ac.jp/~sonoda/papers.htm
On the Mixing of the Scalar Mesons , and
Based on a mass matrix describing the mixing of the scalar states
, and , the hadronic decays of the three
states are investigated. Taking into account the two possible assumptions
concerning the mass level order of the bare states
, and in the
scalar sector, and , we obtain the
glueball-quarkonia content of the three states by solving the unlinear
equations. Some predictions about the decays of the three states in two cases
are presented, which can provide a stringent consistency check of the two
assumptions.Comment: revtex 10 pages, 1 eps figur
Ultrafast optical switching of three-dimensional Si inverse opal photonic band gap crystals
We present ultrafast optical switching experiments on 3D photonic band gap
crystals. Switching the Si inverse opal is achieved by optically exciting free
carriers by a two-photon process. We probe reflectivity in the frequency range
of second order Bragg diffraction where the photonic band gap is predicted. We
find good experimental switching conditions for free-carrier plasma frequencies
between 0.3 and 0.7 times the optical frequency: we thus observe a large
frequency shift of up to D omega/omega= 1.5% of all spectral features including
the peak that corresponds to the photonic band gap. We deduce a corresponding
large refractive index change of Dn'_Si/n'_Si= 2.0% and an induced absorption
length that is longer than the sample thickness. We observe a fast decay time
of 21 ps, which implies that switching could potentially be repeated at GHz
rates. Such a high switching rate is relevant to future switching and
modulation applications
A cluster theory for a Janus fluid
Recent Monte Carlo simulations on the Kern and Frenkel model of a Janus fluid
have revealed that in the vapour phase there is the formation of preferred
clusters made up of a well-defined number of particles: the micelles and the
vesicles. A cluster theory is developed to approximate the exact clustering
properties stemming from the simulations. It is shown that the theory is able
to reproduce the micellisation phenomenon.Comment: 27 pages, 8 figures, 6 table
Deep Neural Networks Rival the Representation of Primate IT Cortex for Core Visual Object Recognition
The primate visual system achieves remarkable visual object recognition
performance even in brief presentations and under changes to object exemplar,
geometric transformations, and background variation (a.k.a. core visual object
recognition). This remarkable performance is mediated by the representation
formed in inferior temporal (IT) cortex. In parallel, recent advances in
machine learning have led to ever higher performing models of object
recognition using artificial deep neural networks (DNNs). It remains unclear,
however, whether the representational performance of DNNs rivals that of the
brain. To accurately produce such a comparison, a major difficulty has been a
unifying metric that accounts for experimental limitations such as the amount
of noise, the number of neural recording sites, and the number trials, and
computational limitations such as the complexity of the decoding classifier and
the number of classifier training examples. In this work we perform a direct
comparison that corrects for these experimental limitations and computational
considerations. As part of our methodology, we propose an extension of "kernel
analysis" that measures the generalization accuracy as a function of
representational complexity. Our evaluations show that, unlike previous
bio-inspired models, the latest DNNs rival the representational performance of
IT cortex on this visual object recognition task. Furthermore, we show that
models that perform well on measures of representational performance also
perform well on measures of representational similarity to IT and on measures
of predicting individual IT multi-unit responses. Whether these DNNs rely on
computational mechanisms similar to the primate visual system is yet to be
determined, but, unlike all previous bio-inspired models, that possibility
cannot be ruled out merely on representational performance grounds.Comment: 35 pages, 12 figures, extends and expands upon arXiv:1301.353
Entanglement production and decoherence-free subspace of two single-mode cavities embedded in a common environment
A system consisting of two identical single-mode cavities coupled to a common
environment is investigated within the framework of algebraic dynamics. Based
on the left and right representations of the Heisenberg-Weyl algebra, the
algebraic structure of the master equation is explored and exact analytical
solutions of this system are obtained. It is shown that for such a system, the
environment can produce entanglement in contrast to its commonly believed role
of destroying entanglement. In addition, the collective zero-mode eigen
solutions of the system are found to be free of decoherence against the
dissipation of the environment. These decoherence-free states may be useful in
quantum information and quantum computation.Comment: 10 pages, 7 figures, Revtex
Magnetoresistance of a semiconducting magnetic wire with domain wall
We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.Comment: 5 pages, 2 figure
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