Measurements of the $$\mathrm{t}\overline{\mathrm{t}}$$ t t ¯ production cross section in lepton+jets final states in pp collisions at 8 $$\,\text {TeV}$$ TeV and ratio of 8 to 7  $$\,\text {TeV}$$ TeV cross sections

Abstract

A measurement of the top quark pair production () cross section in proton–proton collisions at the centre-of-mass energy of 8 is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6. This analysis is performed in the decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured cross section is . This measurement is compared with an analysis of 7 data, corresponding to an integrated luminosity of 5.0, to determine the ratio of 8 to 7 cross sections, which is found to be . The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.

Measurement of the $$t\bar{t}$$ production cross-section and lepton differential distributions in $$e\mu $$ dilepton events from pp collisions at $$\sqrt{s}=13\,\text {TeV}$$ with the ATLAS detector

“…Predictions for the inclusive tt production cross-section in proton-proton ( pp) collisions, σ tt , are available at next-tonext-to-leading-order (NNLO) accuracy in the strong coupling constant α S , including the resummation of next-tonext-to-leading logarithmic (NNLL) soft gluon terms [1][2][3][4][5][6], and are in excellent agreement with measurements from ATLAS and CMS at √ s = 7, 8 and 13 TeV [7][8][9][10][11][12][13]. At √ s = 13 TeV, and assuming a fixed top quark mass of m t = 172.5 GeV, the NNLO+NNLL prediction is 832 ± 35 +20 −29 pb, as calculated using the Top++ 2.0 program [14].…”

Rare two-body decays of the top quark into a bottom meson plus an up or charm quark

“…Compared to the fully-hadronic mode, the -plus-jets channel has a slightly smaller B ≈ 35% overall branching ratio, and half the number of top quarks available for the 2-body decay, but it features a cleaner experimental signature based on the presence of a high-p T isolated electron or muon. The following selection criteria, typically used by the ATLAS/CMS experiments [46][47][48][49][50][51], are applied:…”

Top-quark physics at the Large Hadron Collider

“…Furthermore, the ATLAS em dilepton sample was used for a more comprehensive test of the Standard Model by measuring simultaneously the production of tt ¯, WW and Z tt  [43]. Measurements at 8 TeV are available in the singlelepton channel as well, albeit with larger uncertainties [44,45].…”