2,513 research outputs found
Spectra of Field Fluctuations in Braneworld Models with Broken Bulk Lorentz Invariance
We investigate five-dimensional braneworld setups with broken Lorentz
invariance continuing the developments of our previous paper (arXiv:0712.1136),
where a family of static self-tuning braneworld solutions was found. We show
that several known braneworld models can be embedded into this family. Then we
give a qualitative analysis of spectra of field fluctuations in backgrounds
with broken Lorentz invariance. We also elaborate on one particular model and
study spectra of scalar and spinor fields in it. It turns out that the spectra
we have found possess very peculiar and unexpected properties.Comment: 30 pages, 8 figures, minor corrections, references added, note adde
Unsupervised Polygonal Reconstruction of Noisy Contours by a Discrete Irregular Approach
International audienceIn this paper, we present an original algorithm to build a polygonal reconstruction of noisy digital contours. For this purpose, we first improve an algorithm devoted to the vectorization of discrete irregular isothetic objects. Afterwards we propose to use it to define a reconstruction process of noisy digital contours. More precisely, we use a local noise detector, introduced by Kerautret and Lachaud in IWCIA 2009, that builds a multi-scale representation of the digital contour, which is composed of pixels of various size depending of the local amount of noise. Finally, we compare our approach with previous works, by con- sidering the Hausdorff distance and the error on tangent orientations of the computed line segments to the original perfect contour. Thanks to both synthetic and real noisy objects, we show that our approach has interesting performance, and could be applied in document analysis systems
Vector boson production in association with KK modes of the ADD model to NLO in QCD at LHC
Next-to-leading order QCD corrections to the associated production of vector
boson (Z/W) with the the Kaluza-Klein modes of the graviton in large extra
dimensional model at the LHC, are presented. We have obtained various kinematic
distributions using a Monte Carlo code which is based on the two cut off phase
space slicing method that handles soft and collinear singularities appearing at
NLO level. We estimate the impact of the QCD corrections on various observables
and find that they are significant. We also show the reduction in factorization
scale uncertainty when QCD corrections are included.Comment: 12 pages, 5 figure
Real Time tracking of human gestures using color image processing
This paper deals with areas detection and tracking using color based image processing. The application adressed
concerns human head and hands tracking. We propose an original method in order to locate, for an foreground image,
colored areas. Foreground image is provided by a probabilistic way using Gaussian Mixture Models (GMM) of probability
density fonctions. The temporal tracking is then achieved by a particle filter, which is well adapted to partial occlusions
and non gaussian models.Cet article adresse le problème de la détection et du suivi de zones colorées par traitement d'images couleur.
L'application finale concerne le suivi 2D sans marqueurs de la tête et des deux mains d'une personne. Nous
proposons une méthode originale de localisation de zones colorées, appliquée à l'issue d'une phase
d'extraction de la personne par rapport au fond. L'appartenance d'un pixel de l'image au fond est modélisée
par une densité de probabilités exprimée dans un espace couleur. Nous montrons que l'utilisation de mixtures
de gaussiennes permet d'approcher cette densité de probabilités. La prise en compte de l'évolution
temporelle du système est assurée par un filtre à particules, réputé robuste aux occultations partielles et aux
modèles non gaussiens
Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction
We examine carefully bottomonia hadroproduction in proton colliders,
especially focusing on the LHC, as a way of probing the gluon density in
protons. To this end we develop some previous work, getting quantitative
predictions and concluding that our proposal can be useful to perform
consistency checks of the parameterization sets of different parton
distribution functions.Comment: LaTeX, 14 pages, 6 EPS figure
Production properties of K*(892) vector mesons and their spin alignment as measured in the NOMAD experiment
First measurements of K*(892) mesons production properties and their spin
alignment in nu_mu charged current (CC) and neutral current (NC) interactions
are presented. The analysis of the full data sample of the NOMAD experiment is
performed in different kinematic regions. For K*+ and K*- mesons produced in
nu_mu CC interactions and decaying into K0 pi+/- we have found the following
yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1
(stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons
produced in nu NC interactions the corresponding yields per event are: (2.5 +/-
0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The
results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst)
and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC
interactions, are compared to theoretical predictions tuned on LEP measurements
in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC
interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05
(syst).Comment: 20 p
Interaction of a TeV Scale Black Hole with the Quark-Gluon Plasma at LHC
If the fundamental Planck scale is near a TeV, then parton collisions with
high enough center-of-mass energy should produce black holes. The production
rate for such black holes has been extensively studied for the case of a
proton-proton collision at \sqrt s = 14 TeV and for a lead-lead collision at
\sqrt s = 5.5 TeV at LHC. As the parton energy density is much higher at
lead-lead collisions than in pp collisions at LHC, one natural question is
whether the produced black holes will be able to absorb the partons formed in
the lead-lead collisions and eventually `eat' the quark-gluon plasma formed at
LHC. In this paper, we make a quantitative analysis of this possibility and
find that since the energy density of partons formed in lead-lead collisions at
LHC is about 500 GeV/fm^3, the rate of absorption for one of these black holes
is much smaller than the rate of evaporation. Hence, we argue that black holes
formed in such collisions will decay very quickly, and will not absorb very
many nearby partons. More precisely, we show that for the black hole mass to
increase via parton absorption at the LHC the typical energy density of quarks
and gluons should be of the order of 10^{10} GeV/fm^3. As LHC will not be able
to produce such a high energy density partonic system, the black hole will not
be able to absorb a sufficient number of nearby partons before it decays. The
typical life time of the black hole formed at LHC is found to be a small
fraction of a fm/c.Comment: 7 pages latex (double column), 3 eps figure
Light dark matter and dark force at colliders
Light Dark Matter, GeV, with sizable direct detection rate is an
interesting and less explored scenario. Collider searches can be very powerful,
such as through the channel in which a pair of dark matter particle are
produced in association with a jet. It is a generic possibility that the
mediator of the interaction between DM and the nucleus will also be accessible
at the Tevatron and the LHC. Therefore, collider search of the mediator can
provide a more comprehensive probe of the dark matter and its interactions. In
this article, to demonstrate the complementarity of these two approaches, we
focus on the possibility of the mediator being a new gauge boson, which
is probably the simplest model which allows a large direct detection cross
section for a light dark matter candidate. We combine searches in the
monojet+MET channel and dijet resonance search for the mediator. We find that
for the mass of between 250 GeV and 4 TeV, resonance searches at the
colliders provide stronger constraints on this model than the monojet+MET
searches.Comment: 23 pages and 14 figure
Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays
Results from the nu_tau appearance search in a neutrino beam using the full
NOMAD data sample are reported. A new analysis unifies all the hadronic tau
decays, significantly improving the overall sensitivity of the experiment to
oscillations. The "blind analysis" of all topologies yields no evidence for an
oscillation signal. In the two-family oscillation scenario, this sets a 90%
C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes
sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at
sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation
hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta
m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective
couplings of the tau lepton to nu_mu or nu_e.Comment: 46 pages, 16 figures, Latex, to appear on Nucl. Phys.
Search for the exotic resonance in the NOMAD experiment
A search for exotic Theta baryon via Theta -> proton +Ks decay mode in the
NOMAD muon neutrino DIS data is reported. The special background generation
procedure was developed. The proton identification criteria are tuned to
maximize the sensitivity to the Theta signal as a function of xF which allows
to study the Theta production mechanism. We do not observe any evidence for the
Theta state in the NOMAD data. We provide an upper limit on Theta production
rate at 90% CL as 2.13 per 1000 of neutrino interactions.Comment: Accepted to European Physics Journal
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