525 research outputs found
NLO QCD corrections to the production of Higgs plus two jets at the LHC
We present the calculation of the NLO QCD corrections to the associated
production of a Higgs boson and two jets, in the infinite top-mass limit. We
discuss the technical details of the computation and we show the numerical
impact of the radiative corrections on several observables at the LHC. The
results are obtained by using a fully automated framework for fixed order NLO
QCD calculations based on the interplay of the packages GoSam and Sherpa. The
evaluation of the virtual corrections constitutes an application of the
d-dimensional integrand-level reduction to theories with higher dimensional
operators. We also present first results for the one-loop matrix elements of
the partonic processes with a quark-pair in the final state, which enter the
hadronic production of a Higgs boson together with three jets in the infinite
top-mass approximation.Comment: 9 pages, 7 figures, references added, published in Phys.Lett.
Automated one-loop calculations with GoSam 2.0
We present the version 2.0 of the program GoSam, which is a public program
package to compute one-loop corrections to multi-particle processes. The
extended version of the "Binoth-Les-Houches-Accord" interface to Monte Carlo
programs is also implemented. This allows a large flexibility regarding the
combination of the code with various Monte Carlo programs to produce fully
differential NLO results, including the possibility of parton showering and
hadronisation. We describe the new features of the code and illustrate the wide
range of applicability for multi-particle processes at NLO, both within and
beyond the Standard Model.Comment: 9 pages, talk given at the conference "Loops and Legs in Quantum
Field Theory", Weimar, Germany, April 201
GoSam-2.0: a tool for automated one-loop calculations within the Standard Model and beyond
We present the version 2.0 of the program package GoSam for the automated
calculation of one-loop amplitudes. GoSam is devised to compute one-loop QCD
and/or electroweak corrections to multi-particle processes within and beyond
the Standard Model. The new code contains improvements in the generation and in
the reduction of the amplitudes, performs better in computing time and
numerical accuracy, and has an extended range of applicability. The extended
version of the "Binoth-Les-Houches-Accord" interface to Monte Carlo programs is
also implemented. We give a detailed description of installation and usage of
the code, and illustrate the new features in dedicated examples.Comment: replaced by published version and reference adde
Increased insolation threshold for runaway greenhouse processes on Earth like planets
Because the solar luminosity increases over geological timescales, Earth
climate is expected to warm, increasing water evaporation which, in turn,
enhances the atmospheric greenhouse effect. Above a certain critical
insolation, this destabilizing greenhouse feedback can "runaway" until all the
oceans are evaporated. Through increases in stratospheric humidity, warming may
also cause oceans to escape to space before the runaway greenhouse occurs. The
critical insolation thresholds for these processes, however, remain uncertain
because they have so far been evaluated with unidimensional models that cannot
account for the dynamical and cloud feedback effects that are key stabilizing
features of Earth's climate. Here we use a 3D global climate model to show that
the threshold for the runaway greenhouse is about 375 W/m, significantly
higher than previously thought. Our model is specifically developed to quantify
the climate response of Earth-like planets to increased insolation in hot and
extremely moist atmospheres. In contrast with previous studies, we find that
clouds have a destabilizing feedback on the long term warming. However,
subsident, unsaturated regions created by the Hadley circulation have a
stabilizing effect that is strong enough to defer the runaway greenhouse limit
to higher insolation than inferred from 1D models. Furthermore, because of
wavelength-dependent radiative effects, the stratosphere remains cold and dry
enough to hamper atmospheric water escape, even at large fluxes. This has
strong implications for Venus early water history and extends the size of the
habitable zone around other stars.Comment: Published in Nature. Online publication date: December 12, 2013.
Accepted version before journal editing and with Supplementary Informatio
The vertical distribution of ozone instantaneous radiative forcing from satellite and chemistry climate models
We evaluate the instantaneous radiative forcing (IRF) of tropospheric ozone predicted by four state-of-the-art global chemistry climate models (AM2-Chem, CAM-Chem, ECHAM5-MOZ, and GISS-PUCCINI) against ozone distribution observed from the NASA Tropospheric Emission Spectrometer (TES) during August 2006. The IRF is computed through the application of an observationally constrained instantaneous radiative forcing kernels (IRFK) to the difference between TES and model-predicted ozone. The IRFK represent the sensitivity of outgoing longwave radiation to the vertical and spatial distribution of ozone under all-sky condition. Through this technique, we find total tropospheric IRF biases from -0.4 to + 0.7 W/m(2) over large regions within the tropics and midlatitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper troposphere-lower stratospheric region. The zonal mean biases also range from -30 to + 50 mW/m(2) for the models. However, the ensemble mean total tropospheric IRF bias is less than 0.2 W/m(2) within the entire troposphere
Pragmatics of Yes/No Indirect-responses (YNIRs)
AbstractHow do people transmit information with âquestion-answerâ structures? What happens when a speaker utters a meaningful question and the hearer understands it? The present paper focuses on YNIRs in terms of (a) a radical lack of consensus about their potential in production of messages in interpersonal communication; (b) the ways in which they are used to establish and maintain coherent conversation, and (c) to what extent commentary, and supplementary indirect responses can invoke goal (in) compatibility, and how this kind of conflict can prevent stagnation, stimulate interest, and finally contribute to âescalationâ of mutual understanding. Although the functional horizons of general questions and the answers to them vary from context to context, the addressee can âcontrolâ his judgements and attitudes (apology, ignorance, consent, or refusal) by his deeper exposure to the situation, what, in the end, enables his affiliation with others. The other major concern of the paper is to specify the cases when the pragmatic interpretation of questionless responses is defined as unification of the semantic representation and the internal utterance context
Geometric modeling of 3D woven preforms in composite T-joints
A common method to fabricate net-shaped three-dimensional (3D) woven preforms for composite T-joints is to weave flat 3D preforms via a standard weaving machine with variation in binder yarn path and then separate the preform in the form of a bifurcation. Folding introduces fiber architecture deformation at the 3D woven bifurcation area. In this paper, a geometric modeling approach is proposed to represent the realistic fiber architecture, as a preprocessor for finite element analyses to predict composite structural performance. Supported by X-ray micro-computed tomography (mCT), three important deformation mechanisms are observed including yarn stack shifting, cross-section bending, and cross-section flattening resulting from the folding process. Furthermore, a set of mathematical formulae for simulation of the deformations in the junction region are developed and satisfactory agreement is observed when compared with mCT scan results
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
This Report summarizes the proceedings of the 2013 Les Houches workshop on
Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for
calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections
and (2) the comparison of those cross sections with LHC data from Run 1, and
projections for future measurements in Run 2.Comment: Proceedings of the Standard Model Working Group of the 2013 Les
Houches Workshop, Physics at TeV Colliders, Les houches 3-21 June 2013. 200
page
Different atmospheric moisture divergence responses to extreme and moderate El Niños
On seasonal and inter-annual time scales, vertically integrated moisture divergence provides a useful measure of the tropical atmospheric hydrological cycle. It reflects the combined dynamical and thermodynamical effects, and is not subject to the limitations that afflict observations of evaporation minus precipitation. An empirical orthogonal function (EOF) analysis of the tropical Pacific moisture divergence fields calculated from the ERA-Interim reanalysis reveals the dominant effects of the El Niño-Southern Oscillation (ENSO) on inter-annual time scales. Two EOFs are necessary to capture the ENSO signature, and regression relationships between their Principal Components and indices of equatorial Pacific sea surface temperature (SST) demonstrate that the transition from strong La Niña through to extreme El Niño events is not a linear one. The largest deviation from linearity is for the strongest El Niños, and we interpret that this arises at least partly because the EOF analysis cannot easily separate different patterns of responses that are not orthogonal to each other. To overcome the orthogonality constraints, a self-organizing map (SOM) analysis of the same moisture divergence fields was performed. The SOM analysis captures the range of responses to ENSO, including the distinction between the moderate and strong El Niños identified by the EOF analysis. The work demonstrates the potential for the application of SOM to large scale climatic analysis, by virtue of its easier interpretation, relaxation of orthogonality constraints and its versatility for serving as an alternative classification method. Both the EOF and SOM analyses suggest a classification of âmoderateâ and âextremeâ El Niños by their differences in the magnitudes of the hydrological cycle responses, spatial patterns and evolutionary paths. Classification from the moisture divergence point of view shows consistency with results based on other physical variables such as SST
Mendeliome sequencing enables differential diagnosis and treatment of neonatal lactic acidosis
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