QCD corrections to t\bar t b \bar b productions via photon-photon collisions at linear colliders

Abstract

We calculated the complete next-to-leading order(NLO) QCD corrections to the $t\bar{t}b\bar{b}$ production process at a $\gamma \gamma$ collider in the standard model(SM). The calculation of the one-loop QCD correction includes the evaluations of the hexagon and pentagon amplitudes. We studied the NLO QCD corrected total cross section, the distributions of transverse momenta of final top- and bottom-quark states, and the dependence of the cross section on renormalization scale $\mu$. It shows that NLO QCD correction generally increases the LO cross section in our chosen parameter space, and the K-factor varies from 1.70 to 1.14 when colliding energy goes up from $400GeV$ to $2TeV$. We find that the correction distinctly changes the distributions of transverse momenta of the final top- and bottom-quark states, and the NLO QCD correction obviously improves the independence of the cross section for process $\gamma \gamma \to t\bar{t}b\bar{b}$ on the renormalization scale.

14pages, 9figures, to be appeared in Physics Letters B