Radiative Corrections to $γγ\to t \bar t$ in the Electroweak Standard Model

Abstract

The cross-section for $γγ\to t \bar t$ 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 $(γγ\to H^*\to t\bar t)$ the weak corrections are widely independent of the Higgs-boson mass.