Boosted tops: Physics and reconstruction

The production of boosted top quarks in the high centre-of-mass energy collisions at the LHC is a probe to new phenomena at the TeV scale. Numerous extensions to the Standard Model (SM) predict massive particles whose couplings to top quarks are enhanced. Such massive particles, referred as t¯t resonances, will distort the t¯t invariant mass spectrum relative to the SM expectation. This presentation is dedicated to studies performed by the ATLAS and CMS Collaborations. New techniques were developed to reconstruct boosted top quarks as single objects, both as a top-tagged jet with a substructure in the hadronic decay mode and a jet with a lepton inside in the leptonic decay mode. These techniques were applied in dedicated analyses to search for high mass t¯t resonances. Expected limits and the potential for observation are presented for a luminosity of few hundreds of pb−1

El Feto, un Paciente que Espera

La preocupación sobre la salud fetal surge en nuestra sociedad a medida que se conoce que una de las causas fundamentales de las muertes prenatales es debida a las malformaciones y enfermedades fetales. En este artículo, se entrega información relevante sobre este tema que es de alta complejidad. Las preguntas que surgen frente a estos hechos son:¿Cómo y cuando enferma un feto?, ¿Cómo se pueden prevenir estas enfermedades o bien curarlas?, ¿Que se puede hacer frente a un feto enfermo? El objetivo de nuestro artículo es aportar información sobre un tema no bien conocido pero que, de una u otra forma, interesa a cada uno de nosotros

Experimental and numerical study of crack healing in a nuclear glass

International audiencea b s t r a c t An experimental study of thermally or water-induced crack healing in an inactive borosil-icate glass, chemically analogous to that used in France for the vitrification of nuclear waste was carried out. Partial welding of glass plates was observed after annealing in air at 425 °C (77 °C below T g) when at least 20 MPa compressive stress was applied, while annealing at 450 °C under 20 MPa led to a complete disappearance of the interface. Closure of indenta-tion-induced cracks was observed during annealing at 400 °C in an ESEM as a result of viscous relaxation of residual stresses but it did not constitute a sufficient proof of crack healing. DCDC specimens were thus pre-cracked in an ESEM and then either annealed at various temperatures (350–490 °C) in secondary vacuum or in air, or left in water at 70–90 °C, sometimes under a compressive stress normal to the crack face. The specimens were then reloaded in the ESEM and the crack opening displacements under a given load were compared to those measured during pre-cracking. The cracks were bridged by an alteration layer over a distance from the crack tip which decreased as loading increased. The restraining effect of these bridges on crack opening was assessed via finite element simulations, using interface elements. The tensile strength of the bridging layer was estimated as 27–39 MPa after vacuum annealing at 400 °C, 11–20 MPa after 15 days in water at 90 °C and 44–78 MPa after 11 days in water at 70 °C under 5 MPa normal compression. Partially healed cracks did not resume propagation from their former crack tip, but due to branch cracks re-initiated a few hundred microns behind it which grow avoiding the healed area. This behaviour was explained using finite element simulations

El hombre y la cultura. (Estudio de los nn. 61 Y 62 de la Constitución Pastoral «Gaudium et Spes» del Concilio Vaticano II)

El interés del tema del hombre y de la cultura de que se trata en este trabajo se justifica, en mi opinión, principalmente por dos factores: la importancia que Juan Pablo II atribuye a cada uno de los elementos del tema, y el que este tema se inserte en la cuestión más concreta de las relaciones entre fe y cultura, objeto de la Tesis de doctorado. De hecho el Papa en sus enseñanzas, de modo general, tiene como línea asentar una antropología firme y verdadera —una antropología cristiana— que sea después camino para volver a Dios

High intensity and space charge problems at GANIL

http://accelconf.web.cern.ch/AccelConf/c86/papers/g-04.pdfInternational audienceWe routinely accelerate up to micro-amperes of ionsat energies ranging from 25 to 95 MeV / A. Already atthese levels, space charge (S.C) problems drasticallyaffect the bunching efficiency between the ECRexternal ion-source and our Co compact injector.Moreover in the "2.5" version of GANIL we expectcurrents above 50 e\l A (Ar+6 for instance) and S.Ceffects will be of prime importance during accelerationin the injector and even in our first SSC. Wepresent our computer codes and our first results

Upper Bounding in Inner Regions for Global Optimization under Inequality Constraints

International audienceIn deterministic continuous constrained global optimization, upper bounding the objective function generally resorts to local minimization at several nodes/iterations of the branch and bound. We propose in this paper an alternative approach when the constraints are inequalities and the feasible space has a non-null volume. First, we extract an inner region , i.e., an entirely feasible convex polyhedron or box in which all points satisfy the constraints. Second, we select a point inside the extracted inner region and update the upper bound with its cost. We describe in this paper two original inner region extraction algorithms implemented in our interval B&B called IbexOpt. They apply to nonconvex constraints involving mathematical operators like +,x,power,sqrt,exp,log,sin. This upper bounding shows very good performance obtained on medium-sized systems proposed in the COCONUT suite

Preliminary design of a new high intensity injection system for GANIL.

http://accelconf.web.cern.ch/AccelConf/c89/papers/f6-12.pdfInternational audienc

Seismic evidence for shallow gas-escape features associated with a retreating gas hydrate zone offshore west Svalbard

Active gas venting occurs on the uppermost continental slope off west Svalbard, close to and upslope from the present-day intersection of the base of methane hydrate stability (BMHS) with the seabed in about 400 m water depth in the inter-fan region between the Kongsfjorden and Isfjorden cross-shelf troughs. From an integrated analysis of high-resolution, two-dimensional, pre-stack migrated seismic reflection profiles and multibeam bathymetric data, we map out a bottom simulating reflector (BSR) in the inter-fan region and analyze the subsurface gas migration and accumulation. Gas seeps mostly occur in the zone from which the BMHS at the seabed has retreated over the recent past (1975–2008) as a consequence of a bottom water temperature rise of 1°C. The overall margin-parallel alignment of the gas seeps is not related to fault-controlled gas migration, as seismic evidence of faults is absent. There is no evidence for a BSR close to the gas flare region in the upper slope but numerous gas pockets exist directly below the predicted BMHS. While the contour following trend of the gas seeps could be a consequence of retreat of the landward limit of the BMHS and gas hydrate dissociation, the scattered distribution of seeps within the probable hydrate dissociation corridor and the occurrence of a cluster of seeps outside the predicted BMHS limit and near the shelf break indicate the role of lithological heterogeneity in focusing gas migration

Well dispersed fractal aggregates as filler in polymer-silica nanocomposites: long range effects in rheology

We are presenting a new method of processing polystyrene-silica nanocomposites, which results in a very well-defined dispersion of small primary aggregates (assembly of 15 nanoparticles of 10 nm diameter) in the matrix. The process is based on a high boiling point solvent, in which the nanoparticles are well dispersed, and controlled evaporation. The filler's fine network structure is determined over a wide range of sizes, using a combination of Small Angle Neutron Scattering (SANS) and Transmission Electronic Microscopy (TEM). The mechanical response of the nanocomposite material is investigated both for small (ARES oscillatory shear and Dynamical Mechanical Analysis) and large deformations (uniaxial traction), as a function of the concentration of the particles. We can investigate the structure-property correlations for the two main reinforcement effects: the filler network contribution, and a filler-polymer matrix effect. Above a silica volume fraction threshold, we see a divergence of the modulus correlated to the build up of a connected network. Below the threshold, we obtain a new additional elastic contribution of much longer terminal time than the matrix. Since aggregates are separated by at least 60 nm, this new filler-matrix contribution cannot be described solely with the concept of glassy layer (2nm)