294 research outputs found
BFKL at NNLO
We present a recent determination of an approximate expression for the
O(alpha_s^3) contribution chi_2 to the kernel of the BFKL equation. This
includes all collinear and anticollinear singular contributions and is derived
using duality relations between the GLAP and BFKL kernels.Comment: 8 pages. Talk presented at 12th International Conference on Elastic
and Diffractive Scattering: Forward Physics and QCD, Hamburg, DESY, Germany,
21-25 May 200
Higgs production in gluon fusion at next-to-next-to-leading order QCD for finite top mass
The inclusive Higgs production cross section from gluon fusion is calculated
through NNLO QCD, including its top quark mass dependence. This is achieved
through a matching of the 1/mtop expansion of the partonic cross sections to
the exact large s-hat limits which are derived from k_T-factorization. The
accuracy of this procedure is estimated to be better than 1% for the hadronic
cross section. The final result is shown to be within 1% of the commonly used
effective theory approach, thus confirming earlier findings.Comment: 28 pages, 14 figure
Data-driven modeling of long temperature time-series to capture the thermal behavior of bridges for SHM purposes
Bridges experience complex heat propagation phenomena that are governed by external thermal loads, such as solar radiation and air convection, as well as internal factors, such as thermal inertia and geometrical properties of the various components. This dynamics produces internal temperature distributions which cause changes in some measurable structural responses that often surpass those produced by any other load acting on the structure or by the insurgence or growth of damage. This article advocates the use of regression models that are capable of capturing the dynamics buried within long sequences of temperature measurements and of relating that to some measured structural response, such as strain as in the test structure used in this study. Two such models are proposed, namely the multiple linear regression (MLR) and a deep learning (DL) method based on one-dimensional causal dilated convolutional neural networks, and their ability to predict strain is evaluated in terms of the coefficient of determination R 2. Simple linear regression (LR), which only uses a single temperature reading to predict the structural response, is also tested and used as a benchmark. It is shown that both MLR and the DL method largely outperform LR, with the DL method providing the best results overall, though at a higher computational cost. These findings confirm the need to consider the evolution of temperature if one wishes to setup a temperature-based data-driven strategy for the SHM of large structures such as bridges, an example of which is given and discussed towards the end of the article.</p
Proceedings of the workshop "Standard Model at the LHC" University College London 30 March - 1 April 2009
Proceedings from a 3-day discussion on Standard Model discoveries with the
first LHC dataComment: 9 contributions to the proceedings of the LHC Standard Model worksho
Synthesis and biological evaluation of new natural phenolic (2E,4E,6E)-Octa-2,4,6-trienoic esters
In the present study the esterification of the OH groups of resveratrol, caffeic acid, ferulic acid, and -sitosterol with an antioxidant polyconjugated fatty acid, (2E,4E,6E)-octa-2,4,6-trienoic acid, was achieved. As the selective esterification of OH groups of natural compounds can affect their biological activity, a selective esterification of resveratrol and caffeic acid was performed by an enzymatic approach. The new resulting compounds were characterized spectroscopically (FT-IR, NMR mono, and bidimensional techniques); when necessary the experimental data were integrated by quantum chemical calculations. The antioxidant, anti-inflammatory and proliferative activity was evaluated. The good results encourage the use of these molecules as antioxidant and/or anti-inflammatory agents in dermocosmetic application
Small x resummation in collinear factorisation
The summation of the small x-corrections to hard-scattering QCD amplitudes by
collinear factorisation method is reconsidered and the K-factor is derived in
leading ln x approximation with a result differing from the corresponding
expression by Catani and Hautmann (Nucl. Phys. B 427, 475, 1994). The
significance of the difference is demonstrated in the examples of structure
function F_L and of exclusive vector meson electroproduction. The formulation
covers the channels of non-vanishing conformal spin n paving the way for new
applications.Comment: 34 pages, 6 figure
On the NLO QCD corrections to the production of the heaviest neutral Higgs scalar in the MSSM
We present a calculation of the two-loop top-stop-gluino contributions to
Higgs production via gluon fusion in the MSSM. By means of an asymptotic
expansion in the heavy particle masses, we obtain explicit and compact analytic
formulae that are valid when the Higgs and the top quark are lighter than stops
and gluino, without assuming a specific hierarchy between the Higgs mass and
the top mass. Being applicable to the heaviest Higgs scalar in a significant
region of the MSSM parameter space, our results complement earlier ones
obtained with a Taylor expansion in the Higgs mass, and can be easily
implemented in computer codes to provide an efficient and accurate
determination of the Higgs production cross section.Comment: 18 pages, 4 figure
Une méthode pour le prétraitement et le calcul de matrices de crosstalk pour des images couleur issues d'une caméra tri-CCD
- Ce travail s'inscrit comme outil dans le cadre de la reconstruction 3D à l'aide d'une projection de lumière structurée couplée à une caméra 3CCD. Le principe est simple : il faut disposer une caméra 3CCD et un vidéo-projecteur comme un système de stéréovision classique, devant la scène à étudier. L'utilisation d'une lumière structurée lève beaucoup d'ambiguïtés par rapport à un système de stéréovision à deux caméras. Par contre, l'utilisation de la couleur pour coder la projection réduit le champ d'action du système aux objets blancs ou pâles. Pour pouvoir déterminer la couleur en même temps que la reconstruction 3D de l'objet, il faut avoir des images couleurs parfaitement nettoyées. Nous allons donc décrire une méthode de prétraitements des images couleurs issues de la caméra 3CCD utilisée. Les images ainsi traitées peuvent être utilisées dans le modèle couleur que nous suivrons pour remonter aux informations de couleur de l'éclairage structuré pour lever les ambiguïtés de mise en correspondance, ainsi qu 'à la couleur de la scène aux points considérés
NLO QCD bottom corrections to Higgs boson production in the MSSM
We present a calculation of the two-loop bottom-sbottom-gluino contributions
to Higgs boson production via gluon fusion in the MSSM. The calculation is
based on an asymptotic expansion in the masses of the supersymmetric particles,
which are assumed to be much heavier than the bottom quark and the Higgs
bosons. We obtain explicit analytic results that allow for a straightforward
identification of the dominant contributions in the NLO bottom corrections. We
emphasize the interplay between the calculations of the masses and the
production cross sections of the Higgs bosons, discussing sensible choices of
renormalization scheme for the parameters in the bottom/sbottom sector.Comment: 25 pages, 4 figures. v2: references and two figures added, version
published in JHE
Probing the low transverse momentum domain of Z production with novel variables
The measurement of the low transverse momentum region of vector boson
production in Drell-Yan processes has long been invaluable to testing our
knowledge of QCD dynamics both beyond fixed-order in perturbation theory as
well as in the non-perturbative region. Recently the D\O\ collaboration have
introduced novel variables which lead to improved measurements compared to the
case of the standard QT variable. To complement this improvement on the
experimental side, we develop here a complete phenomenological study dedicated
in particular to the new \phi* variable. We compare our study, which contains
the state-of-the-art next-to-next-to-leading resummation of large logarithms
and a smooth matching to the full next-to-leading order result, to the
experimental data and find excellent agreement over essentially the entire
range of \phi*, even without direct inclusion of non-perturbative effects. We
comment on our findings and on the potential for future studies to constrain
non-perturbative behaviour.Comment: 20 pages, 7 figures. Version accepted for publication in JHEP. A
figure with comparison to RESBOS has been adde
- …