Top pair production
Top quark pair production proceeds at the Tevatron mainly through the quark-antiquark channel, while at the LHC the gluon-gluon channel dominates, reflecting the different parton fluxes at the two accelerators. In the inclusive top-quark sample a substantial number of events is accompanied by additional jets. We performed a NLO calculation for top-pair production in association with a jet, which is of particular interest for the top quark forward-backward asymmetry at the Tevatron.
Single top production
A top quark can also be produced singly by an electro-weak W t b-vertex. There are several motivations from physics to study single top production: First of all, the process is sensitive to the electro-weak W t b-vertex and non-standard couplings can give a hint on physics beyond the Standard Model. Secondly, the top quark is produced left-handed. Since no hadronisation occurs, spin correlations survive in the final decay products. Thirdly, the flavour excitation channel can be used to extract the b-quark density. Finally, single top production allows a direct measurement of the CKM matrix element V_tb and a verification of the unitarity of the CKM-matrix.
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