1,910 research outputs found

    Looking for single top quarks in D0 data

    Get PDF
    The search for the electroweak production of top quarks is entering an exciting time: with the ever increasing luminosity furnished by the Tevatron ppbar Collider at Fermilab and sophisticated analysis techniques we are now able to approach the expected standard model production cross section for this new mode of production. Using 370pb-1 of D0 data and likelihoods as discriminants to extract the signal from the large backgrounds, we set upper limits on the standard model production cross section in the s-channel of 5.0 pb and in the t-channel of 4.4 pb, at 95% confidence level.Comment: 5 pages, 3 figures. Contributed to the proceedings of the 34th International Meeting on Fundamental Physics. El Escorial, Spain, April 200

    Evidence for single top quark production at D0

    Get PDF
    The results of the first analysis to show evidence for production of single top quarks are presented. Using 0.9 fb-1 of data collected with the D0 detector at the Fermilab Tevatron, the analysis is performed in the electron+jets and muon+jets decay modes, taking special care in modeling the large backgrounds, applying a new powerful b-quark tagging algorithm and using three multivariate techniques to extract the small signal in the data. The combined measured production cross section is 4.8 +- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.027%, corresponding to a 3.5 standard deviation significance.Comment: 6 pages, 4 figures. Presented at 42nd Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 10-17 Mar 200

    Single top quark production at the Tevatron

    Full text link
    The observation of single top quark production by the CDF and D0 collaborations is one of the flagship measurements of the Run II of the Tevatron. The Tevatron combined single top quark cross section is measured to be: ŌÉ(tb+X,¬†tqb+X)=2.8‚ąí0.5+0.6\sigma(tb+X,~tqb+X)=2.8^{+0.6}_{-0.5}~pb for a top quark mass of 170~GeV. This result is in agreement with the standard model production of a single top quark together with a jet in \ppbar collisions at s\sqrt{s}=1.96~TeV and allows to measure the CKM matrix element ‚ą£Vtb‚ą£|V_{tb}| without assumptions about the number of quark families. Other analyses involving tau leptons have been performed, and several properties, like the top quark width or the polarization have been measured.Comment: Presented at 45th Rencontres de Moriond: QCD and High Energy Interactions, La Thuile, Aosta Valley, Italy, 13-20 Mar 201

    Searches for gauge mediated supersymmetry breaking at ALEPH with centre-of-mass energies up to 209 GeV

    Full text link
    A total of 628 pb-1 of data collected with the ALEPH detector at centre-of-mass energies from 189 to 209 GeV is analysed in the search for gauge mediated supersymmetry breaking (GMSB) topologies. In this framework, a novel search for six-lepton final states when the stau is the next-to-lightest supersymmetric particle (NLSP) and has negligible lifetime is performed. Other possible signatures at LEP are studied and the ALEPH final results described for two acoplanar photons, non-pointing single photons, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and multi-leptons plus missing energy final states. No evidence is found for new phenomena, and lower limits on the masses of the relevant supersymmetric particles are derived. A scan of a minimal GMSB parameter space is performed and lower limits are set for the NLSP mass at 54 GeV and for the mass scale parameter Lambda at 10 TeV, independent of the NLSP lifetime. Including the results from the neutral Higgs boson searches, a NLSP mass limit of 77 GeV is obtained and values of Lambda up to 16 TeV are excluded.Comment: PhD thesis Royal Holloway University of London, September 2002 111 pages, with 55 figures and 22 table

    Recent Progress and Next Steps for the MATHUSLA LLP Detector

    Full text link
    We report on recent progress and next steps in the design of the proposed MATHUSLA Long Lived Particle (LLP) detector for the HL-LHC as part of the Snowmass 2021 process. Our understanding of backgrounds has greatly improved, aided by detailed simulation studies, and significant R&D has been performed on designing the scintillator detectors and understanding their performance. The collaboration is on track to complete a Technical Design Report, and there are many opportunities for interested new members to contribute towards the goal of designing and constructing MATHUSLA in time for HL-LHC collisions, which would increase the sensitivity to a large variety of highly motivated LLP signals by orders of magnitude.Comment: Contribution to Snowmass 2021 (EF09, EF10, IF6, IF9), 18 pages, 12 figures. v2: included additional endorser

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

    Full text link
    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function √į√į¬•with constraints√į √į √į¬• ¬• √įand√į¬ī√į¬• = √į. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV