1,906 research outputs found

    Searching for t‚Üícht \to c h with Multi-Leptons

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    The results of a multi-lepton search conducted by the CMS collaboration with 5 fb‚ąí1^{-1} of data collected from 7 TeV pppp collisions are used to place the first bound on the rare flavor-changing decay of the top quark to a Higgs boson and charm quark. Combining results from a number of exclusive three- and four-lepton search channels yields an estimated upper limit of Br(t‚Üích)<2.7{\rm Br}(t \to ch) < 2.7% for a Higgs boson mass of 125 GeV. The sensitivity of future dedicated searches for t‚Üícht \to c h could be improved by adding exclusive same sign di-lepton channels, as well as by sub-dividing channels based on bb-quark tagging and partial kinematic top quark and Higgs boson tagging. This bound may be interpreted more widely within a range of new physics processes that yield final states with a WW-boson in association with a Higgs boson. For such processes with kinematics that are similar to top--anti-top production and decay, the estimated limit on cross section times branching ratio corresponds to roughly ŌÉ‚čÖBr(pp‚ÜíWhX)<9\sigma \cdot {\rm Br}(pp \to WhX) < 9 pb.Comment: 11 pages, 1 table; v2 typo correcte

    Multi-Lepton Signals of the Higgs Boson

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    The possibility of searching for the Higgs boson in channels with multiple non-resonant leptons is evaluated in light of recent advances in multi-lepton search techniques at the LHC. The total multi-lepton Higgs signal exceeds the four lepton gold-plated resonant mode, but is spread over many channels with same-sign di-lepton, tri-lepton, and four lepton final states. While any individual channel alone is not significant, the exclusive combination across multiple channels is shown to provide a sensitivity competitive with other discovery level searches for the Higgs boson. We estimate that with 5 inverse femtobarn of data, existing non-optimized multi-lepton searches at the LHC could exclude the Higgs boson to 95% CL at a few times the predicted Standard Model cross section in the mass range 120-150 GeV. Refinements focused specifically on the Higgs boson signal are suggested that would further increase sensitivity. We illustrate the possibility of discerning patterns in production and decay modes using correlations across multiple channels by comparing sensitivities to Standard Model, Fermi-phobic, and b-phobic Higgs bosons.Comment: 21 pages, 4 figures, 4 table

    Simplified Models for LHC New Physics Searches

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    This document proposes a collection of simplified models relevant to the design of new-physics searches at the LHC and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the "Topologies for Early LHC Searches" workshop, held at SLAC in September of 2010, the purpose of which was to develop a set of representative models that can be used to cover all relevant phase space in experimental searches. Particular emphasis is placed on searches relevant for the first ~50-500 pb-1 of data and those motivated by supersymmetric models. This note largely summarizes material posted at http://lhcnewphysics.org/, which includes simplified model definitions, Monte Carlo material, and supporting contacts within the theory community. We also comment on future developments that may be useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results from "Topologies for Early LHC Searches" workshop (SLAC, September 2010). Supplementary material can be found at http://lhcnewphysics.or

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

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    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

    Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon