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Search for W' decaying to tau lepton and neutrino in proton-proton collisions at sqrt(s) = 8 TeV
No full textSubmitted to Phys. Rev. Lett, see paper for full list of authorsInternational audienceThe first search for a heavy charged vector boson in the final state with a tau lepton and a neutrino is reported, using 19.7 inverse femtobarns of LHC data at sqrt(s) = 8 TeV. A signal would appear as an excess of events in kinematic regions where the standard model background is low. No excess is observed. Limits are set on a model in which the W' decays preferentially to fermions of the third generation. These results substantially extend previous constraints on this model. Masses below 2.0 to 2.7 TeV are excluded, depending on the model parameters. In addition, the existence of a W' boson with universal fermion couplings is excluded at 95% confidence level, for W' masses below 2.7 TeV
A search for pair production of new light bosons decaying into muons
No full textSubmitted to Phys. Lett. B ; see paper for full list of authorsInternational audienceA search for the pair production of new light bosons, each decaying into a pair of muons, is performed with the CMS experiment at the LHC, using a dataset corresponding to an integrated luminosity of 20.7 inverse femtobarns collected in proton-proton collisions at center-of-mass energy of sqrt(s) = 8 TeV. No excess is observed in the data relative to standard model background expectation and a model independent upper limit on the product of the cross section, branching fraction, and acceptance is derived. The results are compared with two benchmark models, the first one in the context of the next-to-minimal supersymmetric standard model, and the second one in scenarios containing a hidden sector, including those predicting a non-negligible light boson lifetime
Measurement of the ratio B(B[0,s] to J/psi f0(980) )/B(B[0,s] to J/psi phi(1020)) in pp collisions at sqrt(s) = 7 TeV
No full textSubmitted to Phys. Lett. B - see paper for full list of authorsInternational audienceThe ratio R(f0/phi) of the branching fractions of the B[0,s] meson to the CP-odd eigenstate J/psi f0(980) and to J/psi phi(1020) is measured, where J/psi to mu+ mu-, f0 to pi+ pi-, and phi to K+ K-. The analysis is based on a data sample of pp collisions at a centre-of-mass energy of 7 TeV, collected by the CMS experiment, corresponding to an integrated luminosity of 5.3 inverse femtobarns. The result is R(f0/phi) = 0.140 +/- 0.013 +/- 0.018, where the first uncertainty is statistical and the second is systematic. This result is consistent with theoretical predictions and previous measurements of R(f0/phi). It is the most precise measurement of the ratio to date
Asymptotic analysis of a linear isotropic elastic composite reinforced by athin layer of periodically distributed isotropic parallel stiff fibres.
No full textInternational audienceWe present some mathematical convergence results using a two-scale method for a linearelastic isotropic medium containing one layer of parallel periodically distributed heterogeneities locatedin the interior of the whole domain around a plane surface \Sigma. The aim of this paper is to study thesituation when the rigidity of the linearly isotropic elastic fibres is 1/ \epsilon ^ m the rigidity of the surroundinglinearly isotropic elastic material. We use a two-scale convergence method adapted to the geometry of theproblem (layer of fibres). In the models obtained \Sigma behaves for m = 1 as a "material surface" withoutmembrane energy in the direction of the plane orthogonal to the direction of the fibres. For m = 3 the"material surface" has no bending energy in the direction orthogonal to the fibres
Mathematical Font Art
No full textCurrently, only a limited number of fonts are available for high quality mathematical typesetting, such as Knuth's computer modern font, the Stix font, and several fonts from the TeX Gyre family. An interesting challenge is to develop tools which allow users to pick any existing favorite font and to use it for writing mathematical texts. We will present progress on this problem as part of recent developments in the GNU TeXmacs scientic text editor
Trends of total water vapor column above the Arctic from satellites observations
No full textInternational audienceAtmospheric water vapor (H2O) is the most important natural (as opposed to man-made) greenhouse gas, accounting for about two-thirds of the natural greenhouse effect. Despite this importance, its role in climate and its reaction to climate change are still difficult to assess.Many details of the hydrological cycle are poorly understood, such as the process of cloud formation and the transport and release of latent heat contained in the water vapor.In contrast to other important greenhouse gases like carbon dioxide (CO2) and methane, water vapor has a much higher temporal and spatial variability.Total precipitable water (TPW) or the total column of water vapor (TCWV) is the amount of liquid water that would result if all the water vapor in the atmospheric column of unit area were condensed. TCWV distribution contains valuable information on the vigor of the hydrological processes and moisture transport in the atmosphere. Measurement of TPW can be obtained based on atmospheric water vapor absorption or emission of radiation in the spectral range from UV to MW.TRENDS were found over the terrestrial Arctic by means of TCWV retrievals (using Moderate Resolution Imaging Spectro-radiometer (MODIS) near-infrared (2001-2015) records).More detailed approach was made for comparisons with ground based instruments over Sodankyla – Finland (TCWV from: SCIAMACHY 2003-2011, GOME-2A 2007-2011, SAOZ 2003-2011, GPS 2003-2011, MODIS 2003-2011
foF2 long-term trend linked to Earth's magnetic field secular variation at a station under the northern crest of the equatorial ionization anomaly
No full textInternational audienceLong-term trend of the critical frequency of the F 2 ionospheric region, f o F 2 , at Phu Thuy station (21.03°N, 105.96°E), Vietnam, located under the northern crest of the equatorial ionization anomaly, EIA, is studied. Annual mean data are analyzed at 04 LT and 12 LT for the period 1962–2002 using monthly median values and monthly mean values during magnetically quiet days (am < 20). In both cases we obtain similar trends at 4 LT and 12 LT, which we interpret as an absence of geomagnetic activity effect over trends. The positive trends obtained are not consistent with the negative values expected from greenhouse gases effect at this layer of the upper atmosphere. The increasing trend observed at 12 LT is qualitatively in agreement with the expected effect of the secular displacement of the dip equator over the EIA latitudinal profile. At 04 LT, when the EIA is absent, the positive trend is in qualitative agreement with the secular variation of the Earth's magnetic field inclination, I, and the consequent increase of the sin(I)cos(I) factor at the corresponding location
Middle and low latitude ionosphere response to 2015 St. Patrick's Day geomagnetic storm
No full textInternational audienceThis paper presents a study of the St Patrick's Day storm of 2015, with its ionospheric response at middle and low latitudes. The effects of the storm in each longitudinal sector (Asian, African, American, and Pacific) are characterized using global and regional electron content. At the beginning of the storm, one or two ionospheric positive storm effects are observed depending on the longitudinal zones. After the main phase of the storm, a strong decrease in ionization is observed at all longitudes, lasting several days. The American region exhibits the most remarkable increase in vertical total electron content (vTEC), while in the Asian sector, the largest decrease in vTEC is observed. At low latitudes, using spectral analysis, we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field (PPEF) and of the disturbance dynamo electric field (DDEF) on the basis of ground magnetic data. Concerning the PPEF, Earth's magnetic field oscillations occur simultaneously in the Asian, African, and American sectors, during southward magnetization of the B z component of the interplanetary magnetic field. Concerning the DDEF, diurnal magnetic oscillations in the horizontal component H of the Earth's magnetic field exhibit a behavior that is opposed to the regular one. These diurnal oscillations are recognized to last several days in all longitudinal sectors. The observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models
A map of D/H on Mars in the thermal infrared using EXES aboard SOFIA
No full textInternational audienceOn a planetary scale, the D/H ratio on Mars is a key diagnostic for understanding the past history of water on the planet; locally, it can help to constrain the sources and sinks of water vapor through the monitoring of condensation and sublimation processes. To obtain simultaneous measurements of H2O and HDO lines, we have used the Echelle Cross Echelle Spectrograph (EXES) instrument aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) facility to map the abundances of these two species over the Martian disk. High-resolution spectra (R = 6 × 104) were recorded in the 1383−1390 cm-1 range (7.2 μm) on April 08, 2014. Mars was very close to opposition and near northern summer solstice (Ls = 113°). Maps of the H2O and HDO mixing ratios were retrieved from the line depth ratios of weak H2O and HDO transitions divided by a weak CO2 line. As expected for this season, the H2O and HDO maps show a distinct enhancement toward polar regions, and their mixing ratios are consistent with previous measurements and with predictions by the global climate models, except at the north pole where the EXES values are weaker. We derive a disk-integrated D/H ratio of 6.8 (+1.6, −1.0) × 10-4. It is higher than the value in Earth’s oceans by a factor 4.4 (+1.0, −0.6). The D/H map also shows an enhancement from southern to northern latitudes, with values ranging from about 3.5 times to 6.0 times the VSMOW (Vienna standard mean ocean water) value. The D/H distribution shows a depletion over the Tharsis mountains and is consistent with observed latitudinal variations. The variations in D/H with latitude and altitude agree with the models and with the isotope fractionation expected from condensation and sublimation processes
ADAPTIVE DECONVOLUTION OF LINEAR FUNCTIONALS ON THE NONNEGATIVE REAL LINE
No full textInternational audienceIn this paper we consider the convolution model Z = X + Y with X of unknown density f , independent of Y , when both random variables are nonnegative. Our goal is to estimate linear functionals of f such as f for a known function ψ assuming that the distribution of Y is known and only Z is observed. We propose an estimator of f based on a projection estimator of f on Laguerre spaces, present upper bounds on the quadratic risk and derive the rate of convergence in function of the smoothness of f, g and ψ. Then we propose a nonparametric data driven strategy, inspired Goldenshluger and Lepski (2011) method to select a relevant projection space. This methodology is then adapted to pointwise estimation of f. We illustrate the good performance of the new method through simulations. We also test a new approach for choosing the tuning parameter in Goldenshluger-Lepski data driven estimators following ideas developed in Lacour and Massart (2015)