Ref Arxiv: 1404.7042
DOI: 10.1016/j.physletb.2014.09.020
WoS: 000344624900005
Ref. & Cit.: NASA ADS
11 Citations
Résumé:

This Letter reports the observation of a high transverse momentum $Z\rightarrow b\bar{b}$ signal in proton-proton collisions at $\sqrt{s}=8$ TeV and the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fb$^{-1}$. The $Z\rightarrow b\bar{b}$ decay is reconstructed from a pair of b-tagged jets, clustered with the anti-$k_t$ jet algorithm with $R = 0.4$, that have low angular separation and form a dijet with $p_T > 200$ GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully data-driven technique that reduces the dependence of the analysis on simulation. The fiducial cross section is determined to be \[ \sigma^\mathrm{fid}_{Z\rightarrow b\bar{b}} = 2.02 \pm 0.20 ({\rm stat.}) \pm0.25 ({\rm syst.)}\pm 0.06 ({\rm lumi.}){\rm\,pb} = 2.02 \pm{0.33}{\rm\,pb}, \] in good agreement with next-to-leading-order theoretical predictions.

Commentaires: See paper for full list of authors - There are 8 pages + the cover page + the author list, (20 pages total), 3 figures, 1 table, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2013-04/

Ref Arxiv: 1401.7610
DOI: 10.1007/JHEP04(2014)031
WoS: 000334502400001
Ref. & Cit.: NASA ADS
40 Citations
Résumé:

Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 inverse femtobarns of proton-proton collision data collected at a centre-of-mass energy of sqrt(s)=8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5 sigma level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the SHERPA and POWHEG event generators.

Commentaires: See paper for full list of authors - Comments: 42 pages plus author list (63 pages total), 16 figures, 7 tables, submitted to JHEP, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2013-02/

Ref HAL: hal-01100860_v1
Exporter : BibTex | endNote
Résumé:

L’état vitreux est un état de la matière que l’on rencontre couramment dans le domaine des matériaux mais aussi dans le domaine de la géologie, du vivant, de la pharmacopée ou encore de la cuisine… La zone de température où un système passe de l’état liquide, pour lequel la mobilité des entités structurales est élevée, à l’état vitreux, pour lequel la structure peut être considérée comme figée sur le temps de l’expérience et la cristallisation empêchée, est qualifié de domaine de transition vitreuse. Ce phénomène est étudié depuis de nombreuses années en sciences de la matière condensée et pourtant il n’existe pas actuellement de consensus quant à sa description théorique.En dehors des aspects thermodynamiques qui accompagnent cette transition, qui n’est pas une transition de phase classique, ce phénomène présente un caractère cinétique marqué. Il est aussi associé à des processus relaxationnels complexes qui s’étendent sur une large gamme de temps. Dans cet exposé nous rappellerons ces caractéristiques typiques de la transition vitreuse et des matériaux vitrifiables. Et nous aborderons également les grandes idées proposées dans la littérature pour décrire cette transition.

Ref HAL: hal-01100853_v1
DOI: 10.1111/jace.13140
WoS: WOS:000344779900021
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7 Citations
Résumé:

The evolution of radial cracks generated by Vickers indentation on “tin side” of float glass is analysed when heat treated at 620°C under various atmospheres and results are compared with a previous similar study performed on the “air side” of the same glass. Results evidence that the presence and the oxidation state of tin ions has a strong influence on crack morphological changes. If the oxidation state of tin remains quasi unchanged during the heat treatment, the mechanism responsible of the crack evolution is the spheroidization and there is no strong difference between the crack morphological changes observed on the “air” and “tin side” in this case. For oxidative atmospheres, contrary to what is observed on the “air side”, no crack spheroidization occurs. The cracks stay quasi unchanged for dry air or close for humid air. Increase of the viscosity at the top surface due to Sn oxidation is proposed to explain this spheroidization impediment. It is also shown that in these two cases, there is an efficient blunting and healing of the cracks, as four point bending tests indicate a significant sample strengthening with thermal treatment.

Ref HAL: hal-01083826_v1
Ref Arxiv: 1501.01609
DOI: 10.1364/AIO.2014.JTu4A.7
Ref. & Cit.: NASA ADS
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Résumé:

A laser Doppler imaging scheme combined to an upright microscope is proposed. Quantitative Doppler imaging in both velocity norm and direction, as well as amplitude contrast of either zebrafish flesh or vasculature is demonstrated.

Ref HAL: hal-01100019_v1
Ref Arxiv: 1409.0378
DOI: 10.1140/epjst/e2014-02327-3
WoS: 000346416400012
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
4 Citations
Résumé:

Some recent results on the rotational dynamics of polymers are reviewed and extended. We focus here on the relaxation of a polymer, either flexible or semiflexible, initially wrapped around a rigid rod. We also study the steady polymer rotation generated by a constant torque on the rod. The interplay of frictional and entropic forces leads to a complex dynamical behavior characterized by non-trivial universal exponents. The results are based on extensive simulations of polymers undergoing Rouse dynamics and on an analytical approach using force balance and scaling arguments. The analytical results are in general in good agreement with the simulations, showing how a simplified approach can correctly capture the complex dynamical behavior of rotating polymers.

Commentaires: 13 pages; 7 figures; proceedings of the International Workshop on "Brownian Motion in Confined Geometries", Max Planck Institute for the Physics of Complex Systems in Dresden from 17 - 21 March 2014; to appear in EPJ-ST

Ref HAL: hal-01084111_v1
DOI: 10.1016/j.ceramint.2014.01.019
WoS: 000335201800071
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8 Citations
Résumé:

This study reports on the synthesis of polycrystalline samples of (Na0.5Bi0.5)((1-x))BaxTi(1-x)(Fe0.5Nb0.5)(x)O-3 with x=0, 0.025, 0.05, 0.075, and 0.1, using the solid-state reaction technique. It investigates the effects of the substitution of sodium and bismuth by barium in the A site and of titanium by iron and niobium in the B site with regard to the free NBT symmetry and dielectric properties were investigated. The crystallographic and dielectric properties were also investigated. The diffractograms showed that all the samples had a single phase character. The increase of ceramic lattice parameters induced an increase in the size of the perovskite lattice. This increase was caused by the increase of the radii of the A and B sites. Room temperature X-ray data revealed that the ceramic structures underwent a gradual distortion with the increase in the composition fraction. Dielectric permittivity was measured in the temperature range of 120-780 K with frequencies ranging from 1 to 10(3) KHz. Three anomalies, namely T-d, T-1 and T-m, were detected and noted to coexist at lower T-d and T-m as the rate of substitutions increased. All the samples exhibited a diffuse phase transition and implied better dielectric permittivity maxima values at temperatures approaching room temperature, since the substitution rate values increased more than that of pure NBT. A relaxor behavior with Delta T-m= 14K and epsilon'(rmax) =3876 at 1 kHz was observed for (Na0.5Bi0.5)(0.9)Ba0.1Ti0.9(Fe0.5Nb0.5)(0.1)O-3 ceramic.