Abstract
Measurements of normalized differential cross-sections of top quark pair ($t\bar t$) production are presented as a function of the mass, the transverse momentum and the rapidity of the $t\bar t$ system in proton-proton collisions at center-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at 7 TeV and 20.2 fb$^{-1}$ at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a $b$-hadron. The measured distributions are corrected for detector effects and selection efficiency to cross-sections at the parton level. The differential cross-sections are compared with different Monte Carlo generators and theoretical calculations of $t\bar t$ production. The results are consistent with the majority of predictions in a wide kinematic range.
Highlights
The top quark is the most massive elementary particle in the Standard Model (SM)
More accurate and detailed knowledge of top quark pair production is an essential component of the wide-ranging Large Hadron Collider (LHC) physics program, since tt events are the dominant background to many searches for new physics as well as Higgs boson measurements
This paper presents measurements of the normalized differential tt cross sections as a function of the invariant mass, the rapidity of tthraentstvesyrssetemmoinmpenptucmolli(spioTn;tts),atapndffisffi the 1⁄47 and 8 TeV recorded by the ATLAS detector [16]
Summary
The top quark is the most massive elementary particle in the Standard Model (SM). Its mass is close to the scale of electroweak symmetry breaking, implying a unique sensitivity to interactions beyond the SM. Possible new phenomena beyond the SM can modify the kinematic properties of the tt system Measurements of these distributions provide a means of testing the SM prediction at the TeV scale. The large tt production cross section at the LHC leads to a large number of tt pairs, allowing precise inclusive and differential measurements in a wide kinematic range. This paper presents measurements of the normalized differential tt cross sections as a function of the invariant mass (mtt), the rapidity (jyttj) of tthraentstvesyrssetemmoinmpenptucmolli(spioTn;tts),atapndffisffi the 1⁄47 and 8 TeV recorded by the ATLAS detector [16]. In the 7 TeV analysis, where the integrated luminosity is smaller, events containing same-flavor electron or muon pairs (the ee and μμ channels) are selected in order to maximize the size of the available data set
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