Search results for "METHODOLOGIE"

A Measurement of the Bbbar Forward-backward Asymmetry Using the Semileptonic Decay Into Muons

1992

Fractals and multifractals in the description of the cosmic structure

1990

Abstract The concepts of fractals and multifractals are applied to describe the large scale galaxy distribution. It is shown how the Universe fits the fractal geometry on small scales (several Mpc), but that there exists some cut-off where the scale invariance is broken. Even in the scaling region the cosmic structure is not a simple fractal, and the task is to introduce more complex and complete clustering descriptors. At this stage, the concept of multifractals appears to be more efficient to describe the texture of the Universe.

Constraints on Area Variables in Regge Calculus

2000

We describe a general method of obtaining the constraints between area variables in one approach to area Regge calculus, and illustrate it with a simple example. The simplicial complex is the simplest tessellation of the 4-sphere. The number of independent constraints on the variations of the triangle areas is shown to equal the difference between the numbers of triangles and edges, and a general method of choosing independent constraints is described. The constraints chosen by using our method are shown to imply the Regge equations of motion in our example.

Opto-digital tomographic reconstruction of the Wigner distribution function of complex fields.

2008

An optical-digital method has been developed to obtain the Wigner distribution function of one-dimensional complex fields. In this technique an optical setup is employed to experimentally achieve the Radon-Wigner spectrum of the original signal through intensity measurements. Digital tomographic reconstruction is applied to the experimental spectrum to reconstruct the two-dimensional Wigner distribution function of the input. The validity of our proposal is demonstrated with experimental data, and the results are compared with computer simulations.

Search for violation of Lorentz invariance in top quark pair production and decay

2012

Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5.3 fb$^{-1}$ of integrated luminosity, we search for violation of Lorentz invariance by examining the \ttbar production cross section in lepton+jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the \ttbar production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices $(c_Q)_{\mu\nu 33}$ and $(c_U)_{\mu\nu 33}$ containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Wit…

Precise measurement of the top quark mass in the dilepton channel at D0

2011

We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.

Temporal ghost imaging with photon pairs

2017

International audience; We present an experiment of temporal ghost imaging based on the spatial properties of twin photons. The retrieval of a binary time signal of 8 bits is performed with an error rate of 0.70%.

Parallel Phase-Shifting Digital Holography Based on the Fractional Talbot Effect

2010

Digital holography allows us to record and process digitally the complex amplitude distribution associated to diffracted light beams and therefore has offered new possibilities for a variety of applications such as 3D microscopy, interferometry, or information security (see, for example, review [1]). In principle, phase-shifting techniques are the most efficient in terms of spatial resolution to record digital holograms [2]. However, a sequential acquisition of several interference patterns with different phase retardations of the reference beam is necessary, preventing dynamic measurements. Different techniques for time-resolved dynamic interferometry have been developed allowing one-shot …

Multi-illumination single-holographic-exposure lensless Fresnel (MISHELF) microscopy using 4 channels

2021

MISHELF microscopy is generalized by considering 4 illumination/detection channels while retaining single-shot working principle, twin image mitigation and noise averaging. Proof of principle validation is included considering a resolution test target.

CNN-based People Detection in Voxel Space using Intensity Measurements and Point Cluster Flattening

2021

In this paper real-time people detection is demonstrated in a relatively large indoor industrial robot cell as well as in an outdoor environment. Six depth sensors mounted at the ceiling are used to generate a merged point cloud of the cell. The merged point cloud is segmented into clusters and flattened into gray-scale 2D images in the xy and xz planes. These images are then used as input to a classifier based on convolutional neural networks (CNNs). The final output is the 3D position (x,y,z) and bounding box representing the human. The system is able to detect and track multiple humans in real-time, both indoors and outdoors. The positional accuracy of the proposed method has been verifi…