25,805 research outputs found
Astrophysical point source search with the ANTARES neutrino telescope
The ANTARES neutrino telescope is installed at a depth of 2.5 km of the
Mediterranean Sea and consists of a three-dimensional array of 885
photomultipliers arranged on twelve detector lines. The prime objective is to
detect high-energy neutrinos from extraterrestrial origin. Relativistic muons
emerging from charged-current muon neutrino interactions in the detector
surroundings produce a cone of Cerenkov light which allows the reconstruction
of the original neutrino direction. The collaboration has implemented different
methods to search for neutrino point sources in the data collected since 2007.
Results obtained with these methods as well as the sensitivity of the telescope
are presented.Comment: 1 page, 1 figur
Charging Interacting Rotating Black Holes in Heterotic String Theory
We present a formulation of the stationary bosonic string sector of the whole
toroidally compactified effective field theory of the heterotic string as a
double Ernst system which, in the framework of General Relativity describes, in
particular, a pair of interacting spinning black holes; however, in the
framework of low--energy string theory the double Ernst system can be
particularly interpreted as the rotating field configuration of two interacting
sources of black hole type coupled to dilaton and Kalb--Ramond fields. We
clarify the rotating character of the --component of the
antisymmetric tensor field of Kalb--Ramond and discuss on its possible torsion
nature. We also recall the fact that the double Ernst system possesses a
discrete symmetry which is used to relate physically different string vacua.
Therefore we apply the normalized Harrison transformation (a charging symmetry
which acts on the target space of the low--energy heterotic string theory
preserving the asymptotics of the transformed fields and endowing them with
multiple electromagnetic charges) on a generic solution of the double Ernst
system and compute the generated field configurations for the 4D effective
field theory of the heterotic string. This transformation generates the
vector field content of the whole low--energy heterotic string
spectrum and gives rise to a pair of interacting rotating black holes endowed
with dilaton, Kalb--Ramond and multiple electromagnetic fields where the charge
vectors are orthogonal to each other.Comment: 15 pages in latex, revised versio
Symbol detection in online handwritten graphics using Faster R-CNN
Symbol detection techniques in online handwritten graphics (e.g. diagrams and
mathematical expressions) consist of methods specifically designed for a single
graphic type. In this work, we evaluate the Faster R-CNN object detection
algorithm as a general method for detection of symbols in handwritten graphics.
We evaluate different configurations of the Faster R-CNN method, and point out
issues relative to the handwritten nature of the data. Considering the online
recognition context, we evaluate efficiency and accuracy trade-offs of using
Deep Neural Networks of different complexities as feature extractors. We
evaluate the method on publicly available flowchart and mathematical expression
(CROHME-2016) datasets. Results show that Faster R-CNN can be effectively used
on both datasets, enabling the possibility of developing general methods for
symbol detection, and furthermore, general graphic understanding methods that
could be built on top of the algorithm.Comment: Submitted to DAS-201
Gluon mass and freezing of the QCD coupling
Infrared finite solutions for the gluon propagator of pure QCD are obtained
from the gauge-invariant non-linear Schwinger-Dyson equation formulated in the
Feynman gauge of the background field method. These solutions may be fitted
using a massive propagator, with the special characteristic that the effective
mass employed drops asymptotically as the inverse square of the momentum
transfer, in agreement with general operator-product expansion arguments. Due
to the presence of the dynamical gluon mass the strong effective charge
extracted from these solutions freezes at a finite value, giving rise to an
infrared fixed point for QCD.Comment: 3 pages, 2 figures, based on talk given at the 2007 Europhysics
Conference on High Energy Physics, Manchester, 19-25 Jul
Single top polarisation as a window to new physics
We discuss the effect of heavy new physics, parameterised in terms of
four-fermion operators, in the polarisation of single top (anti-)quarks in the
-channel process at the LHC. It is found that for operators involving a
right-handed top quark field the relative effect on the longitudinal
polarisation is twice larger than the relative effect on the total cross
section. This enhanced dependence on possible four-fermion contributions makes
the polarisation measurements specially interesting, in particular at high
momenta.Comment: LaTeX 10 pages. v2: comments and references added, journal versio
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
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