Berlin 2005 – scientific programme

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T: Teilchenphysik

T 207: Höhere Ordnungen

T 207.7: Talk

Friday, March 4, 2005, 15:30–15:45, TU H2037

QED corrections to tt production at the LHC — •Kollar Monika and Hollik Wolfgang — MPI fuer Physik, Muenchen

A precise understanding of the Standard Model (SM) processes as the main source of background to the new physics beyond the SM is crucial for the LHC purposes. In this context, the top quark sector plays an important role due to the large top quark production rate expected to be about 8 million tt pairs per year. QED corrections to tt production in proton-proton collisions are part of the higher order effects, required for a complete treatment at the 1-loop level.

A characteristic feature of the QED corrections is the appearence of infra-red (IR) singularities. The IR divergent contributions are cancelled if summing the virtual and the real (soft bremsstrahlung) corrections. This results in a dependence on cuts to the photon momentum. To obtain quantities accessible in experiments, also the hard part of the bremsstrahlung free of IR divergences has to be included. The cross section for top quark production at the hadronic level is given by the partonic cross section of the 2 contributing processes qq → tt and gg → tt convoluted with the parton distribution functions and integrated over the fraction of the momentum carried by the partons within the protons.