Abstract
We present the NLO QCD corrections to the processes p p and p anti-p to W+ W- b anti-b including leptonic decays of the W bosons. Non-resonant contributions as well as diagrams with doubly resonant and singly resonant top quark propagators are fully taken into account. We employ the narrow width approximation to perform the decays of the W bosons; spin correlations are however preserved. We also calculate observables relevant for top quark mass measurements, and study the impact of kinematical requirements and different scale choices on t anti-t asymmetries.
Highlights
The next-to-leading order (NLO) QCD corrections to top quark pair production have been already known for a long time [26,27,28,29,30]
We present the NLO QCD corrections to the processes pp and pp → W +W −bb including leptonic decays of the W bosons
To investigate top quark finite width effects, we compare the outcomes of two different types of calculations for the W +(e+νe) W −(μ−νμ) bb final states: (I) the full or W W bb approach based on the NLO or lo pdf bbbb (LO) treatment of the 2 → 4 processes where finite width effects of the top quarks and non-resonant contributions are fully taken into account, and (II) the factorized or ttapproach based on the narrow width approximation where the production of the top quarks factorizes from their decays
Summary
For all our perturbative QCD, parton level calculations, we use the GoSam [42] plus Sherpa [43] combined generator package, in short GoSam+Sherpa. GoSam is an automated one-loop amplitude package, combining automatized diagram generation and algebraic manipulation [55,56,57,58] with d-dimensional integrand-level reduction as implemented in the libraries Samurai [59, 60] and Ninja [61]. As mentioned in the introduction, we include singly resonant top quark and non-resonant contributions, see figure 1 Owing to their small overall effect, diagrams that involve Higgs bosons have been neglected throughout. The weak mixing angle remains real-valued in our calculation, as we neglect non-resonant W and Z boson contributions. Using this setup, the correctness of the virtual amplitude has been checked by comparing it with the results of [38] for a given phase-space point.
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