26 research outputs found

    Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

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    Measurements of t(t)over-bar charge asymmetry using dilepton final states in pp collisions at root s=8 TeV

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    Search for heavy resonances decaying to a top quark and a bottom quark in the lepton+jets final state in proton–proton collisions at 13 TeV

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    A search is presented for narrow heavy resonances decaying to a top quark and a bottom quark using data collected by the CMS experiment at √s = 13TeV in 2016. The data set analyzed corresponds to an integrated luminosity of 35.9 fb−1. Final states that include a single lepton (e, μ), multiple jets, and missing transverse momentum are analyzed. No evidence is found for the production of a W′ boson, and the production of right-handed W′ bosons is excluded at 95% confidence level for masses up to 3.6 TeV depending on the scenario considered. Exclusion limits for W′ bosons are also presented as a function of their coupling strength to left- and right-handed fermions. These limits on a W′ boson decaying via a top and a bottom quark are the most stringent published to date

    Measurement of the integrated and differential t(t)over-bar production cross sections for high-p(T) top quarks in pp collisions at root s=8 TeV

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    Measurement of spin correlations in tt production using the matrix element method in the muon plus jets final state in pp collisions at root S=8 TeV

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    Measurement of the charge asymmetry in top quark pair production in pp collisions at root s=8 TeV using a template method

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    Measurements of tt⁻ cross sections in association with b jets and inclusive jets and their ratio using dilepton final states in pp collisions at √s = 13TeV

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    Search for standard model production of four top quarks in proton–proton collisions at √s = 13 TeV

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    A search for events containing four top quarks (tt¯tt¯) is reported from proton–proton collisions recorded by the CMS experiment at √s=13 TeV and corresponding to an integrated luminosity of 2.6 fb−1. The analysis considers the single-lepton (e or μ)+jets and the opposite-sign dilepton (μ+μ−, μ±e∓ , or e+e−)+jets channels. It uses boosted decision trees to combine information on the global event and jet properties to distinguish between tt¯tt¯ and tt¯ production. The number of events observed after all selection requirements is consistent with expectations from background and standard model signal predictions, and an upper limit is set on the cross section for tt¯tt¯ production in the standard model of 94 fb at 95% confidence level (10.2× the prediction), with an expected limit of 118 fb. This is combined with the results from the published CMS search in the same-sign dilepton channel, resulting in an improved limit of 69 fb at 95% confidence level (7.4× the prediction), with an expected limit of 71 fb. These are the strongest constraints on the rate of tt¯tt¯ production to date

    Search for pair production of excited top quarks in the lepton + jets final state

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    A search is performed for the pair production of spin-3/2 excited top quarks, each decaying to a top quark and a gluon. The search uses the data collected with the CMS detector from proton–proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9  fb−1 . Events are selected by requiring an isolated muon or electron, an imbalance in the transverse momentum, and at least six jets of which exactly two must be compatible with originating from the fragmentation of a bottom quark. No significant excess over the standard model predictions is found. A lower limit of 1.2 TeV is set at 95% confidence level on the mass of the spin-3/2 excited top quark in an extension of the Randall–Sundrum model, assuming a 100% branching fraction of its decay into a top quark and a gluon. These are the best limits to date in a search for excited top quarks and the first at 13 TeV

    Inclusive and differential measurements of the tt charge asymmetry in pp collisions at √s=8 TeV

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    The View the MathML sourcett¯ charge asymmetry is measured in proton–proton collisions at a centre-of-mass energy of 8 TeV8 TeV. The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 fb−1. Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010±0.0068 (stat)±0.0037 (syst)0.0010±0.0068 (stat)±0.0037 (syst). In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the View the MathML sourcett¯ system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of −0.0035±0.0072 (stat)±0.0031 (syst)−0.0035±0.0072 (stat)±0.0031 (syst). All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model
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