Abstract
We present results of a computation of NLO QCD corrections to the production of an off-shell top-antitop pair in association with an off-shell W+ boson in proton-proton collisions. As the calculation is based on the full matrix elements for the process mathrm{pp}to {mathrm{e}}^{+}{v}_{mathrm{e}}{mu}^{-}{overline{v}}_{mu }{tau}^{+}{v}_{tau}mathrm{b}overline{mathrm{b}} , all off-shell, spin-correlation, and interference effects are included. The NLO QCD corrections are about 20% for the integrated cross-section. Using a dynamical scale, the corrections to most distributions are at the same level, while some distributions show much larger K-factors in suppressed regions of phase space. We have performed a second calculation based on a double-pole approximation. While the corresponding results agree with the full calculation within few per cent for integrated cross-sections, the discrepancy can reach 10% and more in regions of phase space that are not dominated by top-antitop production. As a consequence, on-shell calculations should only be trusted to this level of accuracy.
Highlights
The associated production of top quarks with a W± boson in the fullyleptonic decay channel represents a rare process at the LHC, owing to the presence of two like-sign leptons in the final state
We present results of a computation of next-to-leading order (NLO) QCD corrections to the production of an off-shell top-antitop pair in association with an off-shell W+ boson in protonproton collisions
The focus is put on the differences between the results obtained with the fixed scale and those obtained with μ(0c) and μ(0d), as we expect that the choice of a well-motivated dynamical scale is beneficial for a better behaviour of NLO QCD corrections, in particular, in the tails of energy-dependent distributions
Summary
In this paper we present the NLO QCD corrections to the process pp → e+νe μ−νμ τ +ντ b b. The calculation has been performed with MoCaNLO, a Monte Carlo generator that has been used to simulate other processes involving top quarks with NLO EW and QCD accuracy [37,38,39,40] It is interfaced with Recola [41, 42] which provides the tree-level and one-loop SM amplitudes using the Collier library [43] to perform the reduction and numerical evaluation of one-loop integrals [44,45,46]. In most of the diagrams, the propagating gluon is radiated from initial-state quarks and converts to bb [see for example figures 1(c), 1(d) and 1(f)] Such diagrams give a small contribution to the squared amplitude, since they do not contain resonant top or antitop quarks. We observe that all diagrams contain at least one resonant W+ boson
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