Abstract
The results of phenomenological studies of top-quark pair production in proton-proton collisions are presented. Differential cross sections are calculated in perturbative QCD at approximate next-to-next-to-leading order ${\cal O}(\alpha_s^4)$ by using methods of threshold resummation beyond the leading logarithmic accuracy. Predictions for the single-particle inclusive kinematics are presented for transverse momentum and rapidity distributions of final-state top quarks. Uncertainties related to the description of proton structure, top-quark mass and strong coupling constant are investigated in detail. The results are compared to the recent measurements by the ATLAS and CMS collaborations at the LHC at the center of mass energy of 7 TeV. The calculation presented here is implemented in the computer code \textsc{Difftop} and can be applied to the general case of heavy-quark pair production at hadron-hadron colliders. For the first time, a fit of parton distribution functions at NNLO is performed by using the differential cross sections of top-quark pair production together with other data sets. The impact of the top-pair production on the precision of the gluon distribution at high scales is illustrated.
Highlights
Precise measurements for the total √and differential cross section for top-quark pair production at a center-of-mass energies S = 7 and 8 TeV have been recently published by the CMS [10, 11] and ATLAS [12,13,14,15] collaborations
The approximate next-to-next-to-leading order (NNLO) O(αs4) calculation for the differential cross section in the single-particle inclusive (1PI) kinematic for heavy-flavor production at hadron colliders has been implemented in a novel computer code DiffTop which we provide at [44]
We present results for the differential cross section of ttproduction at approximate NNLO that are of interest for phenomenological studies at hadron colliders
Summary
Top-pair production at the LHC probes parton distribution functions (PDFs) of the proton, in particular the gluon distribution. For the purpose of a fast calculation within QCD analyses for PDF determination, DiffTop is interfaced to fastNLO [47,48,49,50] and included into the QCD analysis platform HERAFitter [51]. This allows the user to perform, for the first time, full genuine PDF fits including differential cross sections of ttproduction by using fast theoretical predictions for these observables. If that will be the case, a possible way out will be to work on approximate calculations which can be highly improved once the full calculation is available
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