49,519 research outputs found
T and CPT in B-Factories
For the Bd meson system, CP, T and CPT indirect violation can be described
using two physical parameters, epsilon and delta. The traditional observables
based on flavour tag and used in the kaon system, are not helpful in the Bd
case, and new asymmetries have to be introduced. Here such alternative
observables, based on CP tag, are presented, together with the first estimation
on the sensitivity that current asymmetric B-factories can achieve on their
measurement.Comment: 7 pages, Talk given at the International Europhysics conference on
HEP, HEP2001, July 2001, Budapest (Hungary
High-contrast imaging at small separation: impact of the optical configuration of two deformable mirrors on dark holes
The direct detection and characterization of exoplanets will be a major
scientific driver over the next decade, involving the development of very large
telescopes and requires high-contrast imaging close to the optical axis. Some
complex techniques have been developed to improve the performance at small
separations (coronagraphy, wavefront shaping, etc). In this paper, we study
some of the fundamental limitations of high contrast at the instrument design
level, for cases that use a combination of a coronagraph and two deformable
mirrors for wavefront shaping. In particular, we focus on small-separation
point-source imaging (around 1 /D). First, we analytically or
semi-analytically analysing the impact of several instrument design parameters:
actuator number, deformable mirror locations and optic aberrations (level and
frequency distribution). Second, we develop in-depth Monte Carlo simulation to
compare the performance of dark hole correction using a generic test-bed model
to test the Fresnel propagation of multiple randomly generated optics static
phase errors. We demonstrate that imaging at small separations requires large
setup and small dark hole size. The performance is sensitive to the optic
aberration amount and spatial frequencies distribution but shows a weak
dependence on actuator number or setup architecture when the dark hole is
sufficiently small (from 1 to 5 /D).Comment: 13 pages, 18 figure
X, Y and Z States
Many new states in the charmonium mass region were recently discovered by
BaBar, Belle, CLEO-c, CDF, D0, BESIII, LHCb and CMS Collaborations. We use the
QCD Sum Rule approach to study the possible structure of some of these states.Comment: Contribution for the proceedings of the "XII Quark Confinement and
the Hadron Spectrum - CONF12" conferenc
Tensor hypercontraction: A universal technique for the resolution of matrix elements of local, finite-range -body potentials in many-body quantum problems
Configuration-space matrix elements of N-body potentials arise naturally and
ubiquitously in the Ritz-Galerkin solution of many-body quantum problems. For
the common specialization of local, finite-range potentials, we develop the
eXact Tensor HyperContraction (X-THC) method, which provides a quantized
renormalization of the coordinate-space form of the N-body potential, allowing
for a highly separable tensor factorization of the configuration-space matrix
elements. This representation allows for substantial computational savings in
chemical, atomic, and nuclear physics simulations, particularly with respect to
difficult "exchange-like" contractions.Comment: Third version of the manuscript after referee's comments. In press in
PRL. Main text: 4 pages, 2 figures, 1 table; Supplemental material (also
included): 14 pages, 2 figures, 2 table
Analytical Results for the Statistical Distribution Related to Memoryless Deterministic Tourist Walk: Dimensionality Effect and Mean Field Models
Consider a medium characterized by N points whose coordinates are randomly
generated by a uniform distribution along the edges of a unitary d-dimensional
hypercube. A walker leaves from each point of this disordered medium and moves
according to the deterministic rule to go to the nearest point which has not
been visited in the preceding \mu steps (deterministic tourist walk). Each
trajectory generated by this dynamics has an initial non-periodic part of t
steps (transient) and a final periodic part of p steps (attractor). The
neighborhood rank probabilities are parameterized by the normalized incomplete
beta function I_d = I_{1/4}[1/2,(d+1)/2]. The joint distribution
S_{\mu,d}^{(N)}(t,p) is relevant, and the marginal distributions previously
studied are particular cases. We show that, for the memory-less deterministic
tourist walk in the euclidean space, this distribution is:
S_{1,d}^{(\infty)}(t,p) = [\Gamma(1+I_d^{-1})
(t+I_d^{-1})/\Gamma(t+p+I_d^{-1})] \delta_{p,2}, where t=0,1,2,...,\infty,
\Gamma(z) is the gamma function and \delta_{i,j} is the Kronecker's delta. The
mean field models are random link model, which corresponds to d \to \infty, and
random map model which, even for \mu = 0, presents non-trivial cycle
distribution [S_{0,rm}^{(N)}(p) \propto p^{-1}]: S_{0,rm}^{(N)}(t,p) =
\Gamma(N)/\{\Gamma[N+1-(t+p)]N^{t+p}\}. The fundamental quantities are the
number of explored points n_e=t+p and I_d. Although the obtained distributions
are simple, they do not follow straightforwardly and they have been validated
by numerical experiments.Comment: 9 pages and 4 figure
Gamma Ray Burst Neutrinos Probing Quantum Gravity
Very high energy, short wavelength, neutrinos may interact with the
space-time foam predicted by theories of quantum gravity. They would propagate
like light through a crystal lattice and be delayed, with the delay depending
on the energy. This will appear to the observer as a violation of Lorenz
invariance. Back of the envelope calculations imply that observations of
neutrinos produced by gamma ray bursts may reach Planck-scale sensitivity. We
revisit the problem considering two essential complications: the imprecise
timing of the neutrinos associated with their poorly understood production
mechanism in the source and the indirect nature of their energy measurement
made by high energy neutrino telescopes.Comment: 14 pages, 2 figure
Enhancement of Optical Coherence Tomography Images of the Retina by Normalization and Fusion
This paper describes an image processing method applied to Optical Coherence Tomography (OCT) images of the retina. The aim is to achieve improved OCT images from the fusion of sequential OCT scans obtained at identical retinal locations. The method is based on the normalization of the acquired images and their fusion. As a result, a noise reduction and an image enhancement are reached. Thanks to the resulting improvement in retinal imaging, clinical specialists are able to evaluate more efficiently eyes pathologies and anomalies. This paper presents the proposed method and gives some evaluation results
Alternative Buffer-Layers for the Growth of SrBi2Ta2O9 on Silicon
In this work we investigate the influence of the use of YSZ and CeO2/YSZ as
insulators for Metal- Ferroelectric-Insulator-Semiconductor (MFIS) structures
made with SrBi2Ta2O9 (SBT). We show that by using YSZ only the a-axis oriented
Pyrochlore phase could be obtained. On the other hand the use of a CeO2/YSZ
double-buffer layer gave a c-axis oriented SBT with no amorphous SiO2 inter-
diffusion layer. The characteristics of MFIS diodes were greatly improved by
the use of the double buffer. Using the same deposition conditions the memory
window could be increased from 0.3 V to 0.9 V. From the piezoelectric response,
nano-meter scale ferroelectric domains could be clearly identified in SBT thin
films.Comment: 5 pages, 9 figures, 13 refernece
- …