E_T^miss distributions in the electron (a) and muon (25 < p_T(μ) < 30 GeV) (b) channels after fitting the QCD background. No E_T^miss requirement is applied, and overflows are included in the last bin. In the plots, the fractions β denote the normalizations of the Standard Model backgrounds determined by the fit, and f_QCD gives the fraction of the data due to the QCD background, as discussed in the text. Systematic uncertainties are not shown in these plots.

E_T^miss distributions in the electron (a) and muon (25 < p_T(μ) < 30 GeV) (b) channels after fitting the QCD background. No E_T^miss requirement is applied, and overflows are included in the last bin. In the plots, the fractions β denote the normalizations of the Standard Model backgrounds determined by the fit, and f_QCD gives the fraction of the data due to the QCD background, as discussed in the text. Systematic uncertainties are not shown in these plots.

Reconstructed tt pair invariant mass (left) and its resolution (right) for three Z′ boson masses: m_Z′ = 500 GeV, m_Z′ = 700 GeV and m_Z′ = 1000 GeV for the dRmin algorithm.

Reconstructed tt pair invariant mass (left) and its resolution (right) for three Z′ boson masses: m_Z′ = 500 GeV, m_Z′ = 700 GeV and m_Z′ = 1000 GeV for the dRmin algorithm.

Leading jet (a) and charged lepton (b) p_T distributions after all cuts. The electron and muon channels have been added together and only statistical uncertainties are shown.

Leading jet (a) and charged lepton (b) p_T distributions after all cuts. The electron and muon channels have been added together and only statistical uncertainties are shown.

Reconstructed tt mass on linear (a) and logarithmic (b) scales using the dRmin algorithm after all cuts. The electron and muon channels have been added together and all events beyond the range of the histogram have been added to the last bin. Only statistical uncertainties are shown.

Reconstructed tt mass on linear (a) and logarithmic (b) scales using the dRmin algorithm after all cuts. The electron and muon channels have been added together and all events beyond the range of the histogram have been added to the last bin. Only statistical uncertainties are shown.

Event display for a high-mass event (m_tt = 1602 GeV). The main panel on the top left shows the r - ϕ view, the bottom panel the r - z view, and the middle right panel the calorimeter η - ϕ view. The top quark boosts lead the decay products to be collimated, albeit still mostly distinguishable using standard reconstruction algorithms.

Expected (dashed line) and observed (black points connected by a line) upper limits on σ× BR(Z′→ tt) (a) and σ× BR(g_KK → tt) (b) using the dRmin algorithm. The dark and light green bands show the range in which the limit is expected to lie in 68% and 95% of experiments, respectively, and the red lines correspond to the predicted cross-section times branching ratio in the leptophobic topcolour and RS models. The error bars on the topcolour cross-section curve represent the effect of the PDF uncertainty on the prediction.

Expected (dashed line) and observed (black points connected by a line) upper limits on σ× BR(Z′→ tt) (a) and σ× BR(g_KK → tt) (b) using the dRmin algorithm. The dark and light green bands show the range in which the limit is expected to lie in 68% and 95% of experiments, respectively, and the red lines correspond to the predicted cross-section times branching ratio in the leptophobic topcolour and RS models. The error bars on the topcolour cross-section curve represent the effect of the PDF uncertainty on the prediction.