Hadronic top-quark pair production in association with a hard jet at next-to-leading order QCD: phenomenological studies for the Tevatron and the LHC

Abstract

We report on the calculation of the next-toleading order QCD corrections to the production of topantitop-quark pairs in association with a hard jet at the Tevatron and at the LHC. Results for integrated and differential cross sections are presented. We find a significant reduction of the scale dependence. In most cases the corrections are below 20% indicating that the perturbative expansion is well under control. Moreover, the forward-backward charge asymmetry of the top quark, which is analyzed at the Tevatron, is studied at next-to-leading order. We find large corrections, suggesting that the definition of the observable has to be refined.

Hadronic top-quark pair-production with one jet and parton showering

“…Top-quark pairproduction associated with jets is also an important background to Higgs boson production in vector boson fusion and for many signals of new physics, e.g., those motivated by supersymmetry. For the process tt+jet we are merging the NLO QCD corrections [7,8] (see [20] for the impact of top-quark decays) with the parton SMC HERWIG [21] and PYTHIA [22,23] using the POWHEG BOX. An independent implementation of this process using the results of HELAC-NLO [9,24] has been reported recently in ref.…”

“…For the reaction tt+jet we are building on the computation of [7,8] for the QCD corrections to NLO, which provides us with all necessary details. The list of all flavor structures of the partonic Born and the real emission processes can be obtained from generic matrix elements by considering all possible crossings of light particles into the initial state.…”

“…[5,6]. The NLO QCD corrections for the processes pp → tt+jet [7,8] and pp → tt + 2 jets [9,10] are more recent achievements. For the direct comparison with experimental data, however, e.g., in order to model experimental acceptances, it is important to provide also theory predictions for the production of fully exclusive events.…”

Two-loop leading color corrections to heavy-quark pair production in the gluon fusion channel

“…The diagrams belonging to the sets ii) and iii) form part of the NLO corrections to top-pair-plus-jet production and have been calculated by several groups [49][50][51][52]. Aside from the calculation of the required Feynman diagrams, a full NNLO calculation of the top-quark pair production cross section is particularly challenging because it entails the development of a NNLO subtraction method, which could be used in processes with massive partons [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69].…”

“…In order to obtain NNLO predictions for the total tt production cross section and for differential distributions, it is necessary to combine the two-loop virtual corrections with the already available one-loop corrections to the tt+(1 parton) process and with the tree-level matrix elements for the process tt+(2 partons) [49][50][51][52]. These diagrams with additional partons in the final state contribute to infrared-divergent configurations where up to two partons can become unresolved.…”