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Searches for third generation squark production in fully hadronic final states in proton-proton collisions at sqrt(s)=8 TeV
No full textSubmitted to JHEP - see paper for full list of authorsInternational audienceSearches for third-generation squarks in fully hadronic final states are presented using data samples corresponding to integrated luminosities of 19.4 or 19.7 inverse femtobarns, collected at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. Three mutually exclusive searches are presented, each optimized for a different decay topology. They include a multijet search requiring one fully reconstructed top quark, a dijet search requiring one or two jets originating from b quarks, and a monojet search. No excesses above the standard model expectations are seen, and limits are set on top and bottom squark production in the context of simplified models of supersymmetry
Search for vector-like T quarks decaying to top quarks and Higgs bosons in the all-hadronic channel using jet substructure
No full textSubmitted to JHEP - see paper for full list of authorsInternational audienceA search is performed for a vector-like heavy T quark that is produced in pairs and that decays to a top quark and a Higgs boson. The data analysed correspond to an integrated luminosity of 19.7 inverse femtobarns collected with the CMS detector in proton-proton collisions at sqrt(s) = 8 TeV. For T quarks with large mass values the top quarks and Higgs bosons can have significant Lorentz boosts, so that their individual decay products often overlap and merge. Methods are applied to resolve the substructure of such merged jets. Upper limits on the production cross section of a T quark with mass between 500 and 1000 GeV are derived. If the T quark decays exclusively to tH, the observed (expected) lower limit on the mass of the T quark is 745 (773) GeV at 95% confidence level. For the first time an algorithm is used for tagging boosted Higgs bosons that is based on a combination of jet substructure information and b tagging
MAJORITY MEASURES
No full textThe validity of majority rule in an election with but two candidates—and of Condorcet consistency—is challenged. Axioms based on measures— paralleling those of K. O. May characterizing majority rule for two candidates that are based on comparisons—lead to another method. It is unique in agreeing with the majority rule when the electorate is “polarized” and meets R. A. Dahl’s requirement that an apathetic majority not defeat an intense minority. It accommodates any number of candidates and avoids both the Condorcet and Arrow paradoxes
Offline parameter estimation using EnKF and maximum likelihood error covariance estimates: Application to a subgrid-scale orography parameterization
No full textInternational audienceRecent works show that the parameters controlling the parameterizations of the physical processes in climate models can be estimated from observations using filtering techniques. In this paper, we propose an offline parameter estimation approach, without estimating the state of the climate model. It is based on the Ensemble Kalman Filter (EnKF) and an iterative estimation of the error covariance matrices and of the background state using a maximum likelihood algorithm. The technique is implemented in a subgrid-scale orography (SSO) parameterization scheme that works in a single vertical column. First, the parameter estimation technique is evaluated using twin experiments. Then, the technique is used with synthetic observations to estimate how the parameters of the SSO scheme should change when the resolution of the input orography dataset of a general circulation model is increased. Our analysis reveals that when the resolution of the orography dataset increases, the scheme should take into account the dynamical sheltering that can occur at low levels between mountain peaks located within the same gridbox area
Dynamic realistic lip animation using a limited number of control points
No full textInternational audienceOne main concern of audiovisual speech research is the intelligibility of audiovisual speech (i.e., talking head). In fact, lip reading is crucial for challenged population as hard of hearing people. For audiovisual synthesis and animation, this suggests that one should pay careful attention to modeling the region of the face that participates actively during speech. Above all, a facial animation system needs extremely good representations of lip motion and deformation in order to achieve realism and effective communication
What favors convective aggregation and why?
No full textInternational audienceThe organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a radiative aggregation. In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak (moisture-memory aggregation), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size
The two-point function of bicolored planar maps
No full textInternational audienceWe compute the distance-dependent two-point function of vertex-bicolored planar maps, i.e., maps whose vertices are colored in black and white so that no adjacent vertices have the same color. By distance-dependent two-point function, we mean the generating function of these maps with both a marked oriented edge and a marked vertex which are at a prescribed distance from each other. As customary, the maps are enumerated with arbitrary degree-dependent face weights, but the novelty here is that we also introduce color-dependent vertex weights. Explicit expressions are given for vertex-bicolored maps with bounded face degrees in the form of ratios of determinants of fixed size. Our approach is based on a slice decomposition of maps which relates the distance-dependent two-point function to the coefficients of the continued fraction expansions of some distance-independent map generating functions. Special attention is paid to the case of vertex-bicolored quadrangulations and hexangulations, whose two-point functions are also obtained in a more direct way involving equivalences with hard dimer statistics. A few consequences of our results, as well as some extension to vertex-tricolored maps, are also discussed
Update of stratospheric temperature interannual variability and trends from space sounders and ground-based lidars observations
No full textInternational audiencethe stratosphere is expected to cool, in conjunction with the global warming at the surface and in the troposphere, due to the increase of greenhouse gas concentration in the atmosphere, and also to stratospheric ozone loss. this is already observed but the rate of cooling is not constant and there is still a debate on its amplitude. several other factors may influence the evolution of the stratospheric temperature. external forcings, like the solar variability that modulate the UV solar flux and strong volcanic eruptions injecting aerosols in the stratosphere, participate to its decadal variability. the variability of the stratospheric dynamics is also adding some complexity to the system. For instance global climate models predicts an increase of the occurrence frequency of sudden stratospheric warming (SSW) events not yet confirmed by the observations. A monitoring of the stratospheric temperature evolution is crucially needed to better understand the complexity of the processes playing a role in the coupling between the stratosphere, the troposphere and the climate.the stratospheric temperature is measured at a global scale by satellite instruments; mainly microwave sounders aMsU (advanced Microwave sounding Unit) on board meteorological satellites. these sounders are very useful to provide the global overview but may suffer from biases and orbital drifts and have a poor vertical resolution in the upper stratosphere. since 2000 radio-occultation sensors, among them the Us-taiwan COsMiC constellation, provide well-resolved and accurate temperature profiles but limited to the upper troposphere-lower stratosphere. rayleigh lidars implemented within the nDaCC (network for the Detection of atmospheric Composition Change) international network measure accurately the temperature profile from the middle stratosphere to the upper mesosphere but in a very few locations. they are used climate change monitoring, dynamics studies and satellite validation.in this presentation we will present an update of the interannual variability and trends in the stratospheric temperature from aMsU, rayleigh lidar and radio- occultation measurements. similarities and differences in the temperature evolution captured by these various sensors will be evaluated. the contribution of anthropogenic and natural forcings to the observed changes will be discussed. a particular focus will be given to the role of SSW events to the stratospheric temperature evolution as a function of latitude and season
Spatial distribution of 17O-excess in surface snow along a traverse from Zhongshan station to Dome A, East Antarctica
No full textInternational audienceThe influence of temperature on the triple isotopic composition of oxygen in water is still an open question and limits the interpretation of water isotopic profiles in Antarctic ice cores. The main limitation arises from the lack of 17O-excess measurements in surface snow and especially for remote regions characterized by low temperature and accumulation rate. In this study, we present new 17O-excess measurements of surface snow along an East Antarctic traverse, from the coastal Zhongshan station to the highest point of the Antarctic ice sheet at Dome A. The 17O-excess data significantly decrease inland, with a latitudinal gradient of −1.33±0.41 per meg/degree, an altitudinal gradient of View the MathML source, and a temperature gradient of View the MathML source. Theoretical calculations performed using a Rayleigh model attribute this inland decrease to kinetic isotopic fractionation occurring during condensation from vapor to ice under supersaturation conditions at low temperatures. However, large heterogeneity of 17O-excess in Antarctic precipitation cannot only be explained by temperature at condensation and/or influences of relative humidity in the moisture source regio
Capillary muscle
No full textInternational audienceThe contraction of a muscle generates a force that decreases when increasing the contraction velocity. This “hyperbolic” force–velocity relationship has been known since the seminal work of A. V. Hill in 1938 [Hill AV (1938) Proc R Soc Lond B Biol Sci 126(843):136–195]. Hill’s heuristic equation is still used, and the sliding-filament theory for the sarcomere [Huxley H, Hanson J (1954) Nature 173(4412):973–976; Huxley AF, Niedergerke R (1954) Nature 173(4412):971–973] suggested how its different parameters can be related to the molecular origin of the force generator [Huxley AF (1957) Prog Biophys Biophys Chem 7:255–318; Deshcherevskiĭ VI (1968) Biofizika 13(5):928–935]. Here, we develop a capillary analog of the sarcomere obeying Hill’s equation and discuss its analogy with muscles