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Measurement of J/psi and psi(2S) prompt double-differential cross sections in pp collisions at sqrt(s) = 7 TeV
No full textsee paper for full list of authorsInternational audienceThe double-differential cross sections of promptly produced J/psi and psi(2S) mesons are measured in pp collisions at sqrt(s) = 7 TeV, as a function of transverse momentum pt and absolute rapidity abs(y). The analysis uses J/psi and psi(2S) dimuon samples collected by CMS, corresponding to integrated luminosities of 4.55 and 4.90 inverse femtobarns, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to pt=120 and 100 GeV for the J/psi and psi(2S), respectively, when integrated over the interval abs(y)<1.2. The ratio of the psi(2S) to J/psi cross sections is also reported for abs(y)<1.2, over the range 10 < pt < 100 GeV. These are the highest-pt values for which the cross sections and ratio have been measured
ParisFog : observations brouillard au SIRTA et études de processus associées
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Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions
No full textsee paper for full list of authorsInternational audienceA systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pt and eta of both particles, and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at sqrt(s[NN]) = 2.76 TeV and pPb collisions at sqrt(s[NN]) = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pt and eta. When measured with particles of different pt, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different eta. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very high-multiplicity pPb collisions. The eta-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions
Cross-validation of IASI/MetOp derived tropospheric δD with TES and ground-based FTIR observations
No full textInternational audienceThe Infrared Atmospheric Sounding Interferometer (IASI) flying on-board MetOpA and MetOpB is able to capture fine isotopic variations of the HDO to H2O ratio (δD) in the troposphere. Such observations at the high spatio temporal resolution of the sounder are of great interest to improve our understanding of the mechanisms controlling humidity in the troposphere. In this study we aim to empirically assess the validity of our error estimation previously evaluated theoretically. To achieve this, we compare IASI δD retrieved profiles with other available profiles of δD, from the TES infrared sounder onboard AURA and from three ground-based FTIR stations produced within the MUSICA project: the NDACC (Network for the Detection of Atmospheric Composition Change) sites Kiruna and Izana, and the TCCON site Karlsruhe, which in addition to near-infrared TCCON spectra also records mid-infrared spectra. We describe the achievable level of agreement between the different retrievals and show that these theoretical errors are in good agreement with empirical differences. The comparisons are made at different locations from tropical to Arctic latitudes, above sea and above land. Generally IASI and TES are similarly sensitive to δD in the free troposphere which allows to compare their measurements directly. At tropical latitudes where IASI's sensitivity is lower than that of TES, we show that the agreement improves when taking into account the sensitivity of IASI in the TES retrieval. For the comparison IASI-FTIR only direct comparisons are performed because of similar sensitivities. We identify a quasi negligible bias in the free troposphere (−3‰) between IASI retrieved δD with the TES one, which are bias corrected, but an important with the ground-based FTIR reaching −47‰. We also suggest that model-satellite observations comparisons could be optimized with IASI thanks to its high spatial and temporal sampling
Dynamique et Modélisation des Atmosphères Profondes: Application à l'Atmosphère de Titan
No full textLarge-scale atmospheric and oceanic motions are fairly well described under the so-called shallow-atmosphere approximation, which neglects the thickness of the atmosphere comparing to the planetary radius. Titan is the biggest moon of Saturn and has a thick atmosphere with an aspect ratio reaching almost 25%. It is then preferable not to make the shallow-atmosphere approximation to model its atmospheric general circulation. This thesis solves problems in modeling of such deep-atmospheres and addresses some issues for understanding their dynamics.The shallow-atmosphere and traditional approximation neglecting the part of the Coriolis force due to the horizontal component of the planetary rotation rate vector (also called as non-traditional part) seem to be inseparable to satisfy the conservation of absolute angular momentum. However, we show that it is possible to retain non-traditional terms under the shallow-atmosphere approximation while satisfying all conservation laws, in the compressible Euler equations as well as in the shallow-water equations on the rotating sphere. In most cases, given the small aspect ratio, this new non-traditional model is accurate. In this case, several idealized zonal jet stability and free evolving turbulence studies have been conducted using shallow-water and Boussinesq models taking into account the complete Coriolis force. We highlight the parameters for which the non-traditional effects are significant and discuss the dynamical effects in realistic cases. To model general circulation of Titan's atmosphere, we integrate the quasi-hydrostatic equations in the dynamical core of the LMD-Z (Titan) atmospheric general circulation model. After identifying the Hamiltonian structure of the equations, we imitate the formulation at discrete level to conserve total energy. Various test cases are performed in order to validate the stability and the accuracy of the new dynamical core. The latter is applied to Titan's atmosphere. Firstly, an idealized simulation is performed starting from an atmosphere at rest and using a Newtonian relaxation. Then more realistic simulations are implemented using parameterizations of LMD-Z (Titan).Les mouvements de l'atmosphère terrestre sont assez bien décrits dans le cadre de l'approximation d'atmosphère mince, qui néglige l'épaisseur de l'atmosphère devant le rayon de la Terre. Titan, le plus grand satellite de Saturne, possède une atmosphère épaisse, le rapport de l'épaisseur par le rayon planétaire atteignant près de 25%. Pour modéliser et comprendre sa circulation générale, il est ainsi préférable voire indispensable de ne pas faire l'approximation de couche mince. Cette thèse résout des problèmes liés à la modélisation de ce type d'atmosphères dites profondes, et aborde des questions visant à la compréhension de leur dynamique.L'approximation de couche mince et l'approximation traditionnelle qui néglige la partie de la force de Coriolis associée à la composante horizontale du vecteur rotation de la planète (appelée également partie non-traditionnelle) semblent indissociables pour satisfaire la conservation du moment cinétique absolu. Nous montrons pourtant qu'il est possible de retenir les termes non-traditionnels sous l'approximation de couche mince tout en satisfaisant les lois de conservation, et ce dans les équations d'Euler compressibles et dans celles de Saint-Venant sur la sphère. Pour certains cas d'écoulements terrestres, étant donné le petit rapport d'aspect, ce nouveau modèle NT est suffisamment précis. Dans ce cas, nous réalisons plusieurs études idéalisées de stabilité de jet zonaux et de turbulence en déclin, dans le cadre de modèles de Saint-Venant et de Boussinesq en prenant en compte la force de Coriolis complète. Nous mettons en évidence les paramètres pour lesquels les effets non-traditionnels sont significatifs et discutons des effets dans des cas réalistes. Pour modéliser la circulation atmosphérique de Titan, nous intégrons les équations quasi-hydrostatiques en levant l'approximation de couche mince dans le coeur dynamique du modèle de circulation générale LMD-Z (Titan). Après avoir identifié la structure Hamiltonienne des équations, nous imitons ce formalisme au niveau discret de manière à conserver l'énergie totale dans le modèle. Divers cas tests sont mis en place afin de valider la stabilité et la précision du nouveau coeur dynamique.Finalement, le nouveau coeur est appliqué à l'atmosphère de Titan. Dans un premier temps une simulation idéalisée est réalisée en partant de vents au repos et en utilisant un rappel newtonien vers une température d'équilibre issue d'un profil vertical mesuré par la sonde Huygens. Des simulations plus réalistes sont mises en place en couplant le c{\oe}ur dynamique profond avec les paramétrisations physiques de LMD-Z (Titan)
Gender Preferences in Africa: A Comparative Analysis of Fertility Choices
No full textThis paper proposes a new method to infer gender preferences from birth spacing. We apply it to Africa, where the least is known about gender preferences. We show that son preference is strong and increasing in North Africa. By contrast, most Sub-Saharan African countries display a preference for variety or no preference at all. Further analysis concludes that traditional family systems predict well the nature of gender preferences, while religion does not. Last, the magnitude of preferences is stronger for wealthier and more educated women
Measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections in pp collisions at sqrt(s) = 7 TeV
No full textsee paper for full list of authorsInternational audienceDifferential cross sections as a function of transverse momentum pt are presented for the production of Y(nS) (n = 1, 2, 3) states decaying into a pair of muons. Data corresponding to an integrated luminosity of 4.9 inverse femtobarns in pp collisions at sqrt(s) = 7 TeV were collected with the CMS detector at the LHC. The analysis selects events with dimuon rapidity abs(y) < 1.2 and dimuon transverse momentum in the range 10 < pt < 100 GeV. The measurements show a transition from an exponential to a power-law behavior at pt ~ 20 GeV for the three Y states. Above that transition, the Y spectrum is significantly harder than that of the Y(1S) and Y(2S). The ratios of the Y(3S) and Y(2S) differential cross sections to the Y(1S) cross section show a rise as pt increases at low pt, then become flatter at higher pt
Ammonia emissions in tropical biomass burning regions: Comparison between satellite-derived emissions and bottom-up fire inventories
No full textInternational audienceVegetation fires emit large amounts of nitrogen compounds in the atmosphere, including ammonia (NH3). These emissions are still subject to large uncertainties. In this study, we analyze time series of monthly NH3 total columns (molec cm-2) from the IASI sounder on board MetOp-A satellite and their relation with MODIS fire radiative power (MW) measurements. We derive monthly NH3 emissions estimates for four regions accounting for a major part of the total area affected by fires (two in Africa, one in central South America and one in Southeast Asia), using a simplified box model, and we compare them to the emissions from both the GFEDv3.1 and GFASv1.0 biomass burning emission inventories. In order to strengthen the analysis, we perform a similar comparison for carbon monoxide (CO), also measured by IASI and for which the emission factors used in the inventories to convert biomass burned to trace gas emissions are thought to be more reliable. In general, a good correspondence between NH3 and CO columns and the FRP is found, especially for regions in central South America with correlation coefficients of 0.82 and 0.66, respectively. The comparison with the two biomass burning emission inventories GFASv1.0 and GFEDv3.1 shows good agreements, particularly in the time of the maximum of emissions for the central South America region and in the magnitude for the region of Africa south of the equator. We find evidence of significant non-pyrogenic emissions for the regions of Africa north of the equator (for NH3) and Southeast Asia (for NH3 and CO). On a yearly basis, total emissions calculated from IASI measurements for the four regions reproduce fairly well the interannual variability from the GFEDv3.1 and GFASv1.0 emissions inventories for NH3 but show values about 1.5-2 times higher than emissions given by the two biomass burning emission inventories, even when assuming a fairly long lifetime of 36 hours for that species
Study of final-state radiation in decays of Z bosons produced in pp collisions at 7 TeV
No full textsee paper for full list of authorsInternational audienceThe differential cross sections for the production of photons in Z to mu+ mu- gamma decays are presented as a function of the transverse energy of the photon and its separation from the nearest muon. The data for these measurements were collected with the CMS detector and correspond to an integrated luminosity of 4.7 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV delivered by the CERN LHC. The cross sections are compared to simulations with POWHEG and PYTHIA, where PYTHIA is used to simulate parton showers and final-state photons. These simulations match the data to better than 5%
Search for physics beyond the standard model in events with two leptons, jets, and missing transverse momentum in pp collisions at sqrt(s) = 8 TeV
No full textSubmitted to JHEP - see paper for full list of authorsInternational audienceA search is presented for physics beyond the standard model in final states with two opposite-sign same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 19.4 inverse femtobarns of proton-proton collisions at sqrt(s) = 8 TeV collected with the CMS detector at the CERN LHC in 2012. The analysis focuses on searches for a kinematic edge in the invariant mass distribution of the opposite-sign same-flavor lepton pair and for final states with an on-shell Z boson. The observations are consistent with expectations from standard model processes and are interpreted in terms of upper limits on the production of supersymmetric particles