4,092 research outputs found

    Higgs boson searches at LEP

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    In this paper we report on the legacy of Higgs boson searches at LEP. Specifically, the results of the statistical combination of the searches carried out by the ALEPH, DELPHI, L3 and OPAL experiments are presented. In the search for the Standard Model (SM) Higgs boson, a signal with mh<114.4 GeV/c^2 has been excluded at the 95% confidence level (CL) or higher. The LEP collaborations also carried out extensive searches for Higgs particles predicted by many scenarios beyond the Standard Model. Here we can only report on a very small fraction of these searches and refer the reader to the complete list of LEP-combined search results.Comment: 3 pages, 2 figures; submitted for proceedings of EPS HEP2007 Conference (19-25 July; Manchester, UK

    Upper limit on mh in the MSSM and M-SUGRA vs. prospective reach of LEP

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    The upper limit on the lightest CP-even Higgs boson mass, mh, is analyzed within the MSSM as a function of tan(beta) for fixed mtop and Msusy. The impact of recent diagrammatic two-loop results on this limit is investigated. We compare the MSSM theoretical upper bound on mh with the lower bound obtained from experimental searches at LEP. We estimate that with the LEP data taken until the end of 1999, the region mh < 108.2 GeV can be excluded at the 95% confidence level. This corresponds to an excluded region 0.6 <= tan(beta) <= 1.9 within the MSSM for mtop = 174.3 GeV and Msusy <= 1 TeV. The final exclusion sensitivity after the end of LEP, in the year 2000, is also briefly discussed. Finally, we determine the upper limit on mh within the Minimal Supergravity (M-SUGRA) scenario up to the two-loop level, consistent with radiative electroweak symmetry breaking. We find an upper bound of mh \approx 127 GeV for mtop = 174.3 GeV in this scenario, which is slightly below the bound in the unconstrained MSSM.Comment: 10 pages, 3 figure

    Sensitivity of ATLAS to FCNC single top quark production

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    The anomalous production of single top quarks via flavour-changing neutral currents (FCNCs), u(c)+g -> t, is studied using the ATLAS detector at the Large Hadron Collider. Detector simulation is done using the fast simulation package ATLFAST. A number of important systematic effects have been addressed. Based on a cut-based analysis, we shows that, with 10 fb-1, ATLAS can observe such top FCNC interactions with 5 sigma significance if the anomalous coupling strengths are k_ug/Lambda=k_cg/Lambda >= 0.0120 −0.0012+0.0014^{+0.0014}_{-0.0012} (sys.) TeV-1, or equivalently Br(t->ug)+Br(t->cg) >= 2.64 −0.54+0.63^{+0.63}_{-0.54} (sys.) x 10^{-4}$. In terms of production cross section, such a discovery requires at least 13.7 pb of anomalous single top quark production. With this level of sensitivity, ATLAS will be able to test some models of new physics

    Reforço de edifícios existentes de betão armado com contraventamentos metålicos

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    Foi calibrado um modelo numérico refinado para a reprodução do comportamento de estruturas existentes de betão armado, e do seu reforço por contraventamento, face a solicitaçÔes sísmicas. Estes modelos foram calibrados com base numa série de ensaios

    Tortuosity variation in a low density binary particulate bed

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    The importance of particle size ratio and particle composition in the properties of a mixed bed is well known. Nevertheless, the dependence of the bed channel tortuosity T on the porosity Δ in the form T=1/Δn, where n is assumed to be a constant, shows that the value of n depends on the properties of the packed bed. For loose packing, experimental data for binary mixtures of glass beads of a size ratio from 1 up to 53.8 was analysed in terms of porosity, tortuosity and permeability. The packing procedure was performed without intensive compacting methods e.g. vibration, etc. Obtained results show that the parameter n is a function of the volume fraction of large particles xD and, for spherical particles, lies in the range 0.4–0.5. The explanation for this variation is (1) a distortion effect on the small particles arrangement occurring near the large particle surface; (2) in the region of minimum porosity, near contact points of large particles, the occurrence of dead zones that are free of small particles. A relationship accounting for this effect is proposed that may be useful for the analysis of transport phenomena in granular bed filters, chromatographic columns, etc.Fundação para a CiĂȘncia e a Tecnologia FCT); FEDE

    Particulate binary mixtures : dependence of packing porosity on particle size ratio

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    Binary mixtures with significant size ratios are scarcely studied. Yet, contaminants of chromatographic columns or ion-exchange resins have size ratios of delta < 0.1. Binary mixtures of glass beads with delta = 0.1-0.0375 were used experimentally to measure packing porosity. Simultaneously, a significant number of published data was analyzed. A linear mixing model was adopted to predict the porosity of each particle fraction in the binary mixture. Deviations from the model may be caused by wedging of small particles between the large ones. Large particles may disturb the porous medium properties by inducing a wall effect over the small particles. Wedging analysis led to the conclusion that, for delta < 0.01, its effect is insignificant. The wall effect yields an additional void around the large particles as long as delta > 0.0035. For delta < 0.0035, the small particles form a monosized dense packing and both wedging and wall effects become negligible.Fundação para a CiĂȘncia e a Tecnologia (FCT) e FEDER – POCTI/EQU/37500/2001

    Application of binary packing for starch separation by hydrodynamic chromatography

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    Columns packed with commercial glass beads of 5 and 19 microns average diameter and binary mixtures with finest fraction of 5 micron (30 % volume fraction of the mixture) were used to analyse starch by hydrodynamic chromatography (HDC). Experiments were carried out at 3 and 15 ÂșC. The observed resolution increased with the application of binary packing as compared with single-size packing. The best results were obtained at starch’s amylopectin and amylose separation with a glass beads mixture (5 + 19 micron) at 3ÂșC. In what concerns amylopectin and amylose separation, a lower pressure drop were obtained for the mixed binary packing when compared with the packing containing uniform 5 micron glass beads. For the Hylon VII starch RRT were 0.777 and 0.964 for amylopectin (AP) and amylose (AM), respectively, while for the Tapioca starch the obtained RRTs were 0.799 and 0.923. Application of unbound glass beads as column packing might reduce equipment and running costs in preparative scale separations.Fundação para a CiĂȘncia e a Tecnologia (FCT) .FEDER - projecto POCI_EQU_58337/200

    Effect of real particles packing with large size ratio on porosity and tortuosity of filter bed

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    The complexity of processes involved in the formation of granular beds results in limited information about permeability Îș , which directly rela tes with packing porosity Δ and tortuosity T . For a mixed bed of particles significantly different in size, the influence of packing affects permeability. For a better understanding of the underlying relationship between Îș , Δ , and T in mixed beds of particles significantly different in size, simplified porous media model of binary mixture of spheres were used. Boundary analysis of the binary packing showed that the approach based on the fractional porosity of large and small size particle fractions gives a tool for Δ control. This approach allows a new insight into the mixture structure and provides explanation for the different types of the obtained porosity. Binary packing of glass beads with size ratios 13.3, 20, and 26.7 were investigated. As a basic relation for the dependence of T on Δ, at different volume fraction xD of large particles in the mixture, the formula T=1/ Δⁿ was used. The obtained experimental results show that the parameter n is a function of the packing content xD and may vary in the range of 0.4-0.5. The reason for n variation was explained by the wall effect of the small particles arrangement occurring near the large particles surface. A model accounting for this effect is proposed and may be useful for transport phenomena analysis in granular bed filters.Fundação para a CiĂȘncia e a Tecnologia (FCT) – Programa Operacional “CiĂȘncia, Tecnologia, Inovação” (POCTI) - POCTI/EQU/37500/2001.UniĂŁo Europeia (UE). Fundo Europeu de Desenvolvimento Regional (FEDER)

    Functional respiratory re-education interventions in people with respiratory disease: a systematic literature review

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    Objectives: to identify nursing interventions in rehabilitation, within the scope of functional respiratory reeducation, which allow a respiratory function improvement in people with respiratory disease. Methods: systematic literature review using the MEDLINE database search, adopting the PICO mnemonic and the Joanna Briggs Institute’s assessment of the level of evidence and methodological quality. The search for randomized controlled trials was carried out in June 2021 considering the period from 2015 to 2020, in English or Portuguese. Results: a sample of nine randomized controlled trials with methodological quality was obtained which highlighted the use of positive expiratory pressure devices as an importantcomponent and intervention for respiratory functional reeducation. Conclusions: nursing interventions in rehabilitation with an emphasis on functional respiratory reeducation are essential, showing improvements in people’s general health