Radiative Corrections to γγ → tt̄ in the Electroweak Standard Model

The cross-section for γγ → tt̄ with arbitrary polarized photons is calculated within the electroweak Standard Model including the complete virtual and soft-photonic O(α) corrections. We present a detailed numerical discussion of the radiative corrections with particular emphasis on the purely weak corrections. These are usually of the order of 1–10% for energies up to 1 TeV. For unpolarized or equally polarized photons they reach almost 10% close to threshold. The large corrections cannot be traced back to a universal origin like the running of α or the ρ-parameter. Apart from the energy region around the Higgs resonance (γγ → H → tt̄) the weak corrections are widely independent of the Higgs-boson mass. BI-TP 95/27 WUE-ITP-95-017 July 1995 Partially supported by the Bundesministerium für Bildung und Forschung, Bonn, Germany.