397 research outputs found

    Physics with Jets in Association with a Z Boson in pp-collisions with the ATLAS Detector at the Large Hadron Collider

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    Die Arbeit beschreibt die Messung des Wirkungsquerschnittes fĂŒr die Produktion von Jets in Ereignissen mit Z-Bosonen in Proton-Proton Kollisionen bei einer Schwerpunktsenergie von √s = 7 TeV mit einer integrierten LuminositĂ€t von ∫Ldt = 36 pb−1 und ∫Ldt = 4.6 fb−1 aufgenommen mit dem ATLAS Experiment am Large Hadron Collider in Genf. Die inklusiven und diïŹ€erenziellen Wirkungsquerschnitte fĂŒr Z (→ e+ e−) + jets werden fĂŒr Jets mit einem Transversalimpuls von pT(jet) > 30 GeV und einer RapiditĂ€t von |y(jet)| < 4.4 gemessen. Die DatensĂ€tze erlauben Messungen in vorher nicht zugĂ€nglichen Phasenraumregionen und können genutzt werden, um die Modellierungen von Z/γ∗ + jets in typischen Phasenraumregionen, die vom Zerfall des Higgs Bosons oder Suchen nach neuer Physik erwarten werden, zu testen. Die Ergebnisse werden auf Partonlevel entfaltet und mit Vorhersagen verschiedener Monte-Carlo Generatoren und Vorhersagen der perturbativen QCD in nĂ€chst-fĂŒhrender Ordnung verglichen

    Search for physics beyond the standard model in events with two leptons, jets, and missing transverse momentum in pp collisions at √s = 8 TeV

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    A search is presented for physics beyond the standard model in final states with two opposite-sign same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 19.4 fb[superscript −1] of proton-proton collisions at √s = 8 TeV collected with the CMS detector at the CERN LHC in 2012. The analysis focuses on searches for a kinematic edge in the invariant mass distribution of the oppositesign same-flavor lepton pair and for final states with an on-shell Z boson. The observations are consistent with expectations from standard model processes and are interpreted in terms of upper limits on the production of supersymmetric particles.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Search for the production of dark matter in association with top-quark pairs in the single-lepton final state in proton-proton collisions at √s = 8 TeV

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    A search is presented for particle dark matter produced in association with a pair of top quarks in pp collisions at a centre-of-mass energy of √s = 8 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 19.7 fb[superscript −1]. This search requires the presence of one lepton, multiple jets, and large missing transverse energy. No excess of events is found above the SM expectation, and upper limits are derived on the production cross section. Interpreting the findings in the context of a scalar contact interaction between fermionic dark matter particles and top quarks, lower limits on the interaction scale are set. These limits are also interpreted in terms of the dark matter-nucleon scattering cross sections for the spin-independent scalar operator and they complement direct searches for dark matter particles in the low mass region.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks using a matrix element method

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    A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5 fb[superscript -1] collected by the CMS experiment at the LHC in pp collisions at a centre-of-mass energy of 8 TeV. In order to separate the signal from the larger t[bar over t] + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, ÎŒ, relative to the standard model prediction for a Higgs boson mass of 125 GeV. The observed (expected) exclusion limit at a 95 % confidence level is ÎŒ < 4.2 (3.3), corresponding to a best fit value [^ over ÎŒ] = 1.2[+1.6 over −1.5].United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Search for third-generation scalar leptoquarks in the tτ channel in proton-proton collisions at √s = 8 TeV

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    A search for pair production of third-generation scalar leptoquarks decaying to top quark and τ lepton pairs is presented using proton-proton collision data at a center-of-mass energy of √s = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb[superscript −1]. The search is performed using events that contain an electron or a muon, a hadronically decaying τ lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a τ lepton, the existence of pair produced, charge −1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a τ lepton, and may also be applied directly to the pair production of bottom squarks decaying predominantly via the R-parity violating coupling λ [subscript 333] â€Č.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at √s=8 TeV using H → WW decays

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    The cross section for Higgs boson production in pp collisions is studied using the H → W[superscript +]W[superscript −] decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 fb[superscript −1]. The Higgs boson transverse momentum (p[subscript T]) is reconstructed using the lepton pair p[subscript T] and missing p[subscript T]. The differential cross section times branching fraction is measured as a function of the Higgs boson pTin a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 ± 8 (stat) ± 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model. Keywords: Hadron-Hadron scattering (experiments), Higgs physicsNational Science Foundation (U.S.)United States. Department of Energ

    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 ðð„with constraintsð ð ð„ „ ðandðŽð„ = ð. 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

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector