Abstract
We present results at next-to-leading order accuracy in QCD for single top-quark production in the t, s and tW channels at the lhc at a centre-of-mass energy of 8TeV, obtained with the sherpa event generator. We find them in very good agreement with measured values and quantify their theory uncertainties. Uncertainties stemming from the choice between the four- and the five-flavour scheme are found to be typically of the order of 5–10% over large ranges of phase space. We discuss the impact of parton distribution functions, and in particular of the bottom PDF. We also show how different cuts on QCD radiation patterns improve the signal-to-background ratio in realistic fiducial volumes.
Highlights
In this publication, we present results obtained with the SHERPA event generation framework [28] for single-top production in all three channels
Because the Nl-jets = 1 requirement does not enforce a rapidity gap, we find that when using this requirement a large number of background events survive where the signal cross section is minimal
We reported on the simulation of single top-quark production in the s, t- and t W -channels with the SHERPA event generator at MC@NLO accuracy
Summary
We present results obtained with the SHERPA event generation framework [28] for single-top production in all three channels. The dominant background processes for the analysis, ttproduction and W -boson production in association with at least one light- and one b-jet, use the MC@NLO technique. As in [48] the kinematics of the decay are adjusted a posteriori to the physical width of the top quark and the W boson by redistributing their masses according to the respective Breit–Wigner distribution. The scales for top-pair production are the default choice in the SHERPA event generator for the production of massive or massless QCD object in hadronic collisions branching ratios are correctly taken into account throughout, with the exception of the total cross sections in Sect. The PDFs for our central value are given by the NNPDF 3.0 set at NLO [58] in the appropriate flavour number scheme, interfaced through LHAPDF 6 [59]. For observables other than total inclusive cross sections, we use the Rivet framework [62] for the object definitions, observable projections and binnings
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