{cal O}(α_{s}) QCD and {cal O}(α_{ew}) electroweak corrections to tbar{t}h⁰ production in γ γ collision

We calculate the ${\cal O}(\alpha_{s})$ QCD and ${\cal O}(\alpha_{{\rm ew}})$ electroweak one-loop corrections in the Standard Model framework, to the production of an intermediate Higgs boson associated with $t\bar{t}$ pair via $\gamma \gamma$ fusion at an electron-positron linear collider (LC). We find the ${\cal O}(\alpha_{s})$ QCD corrections can be larger than the ${\cal O}(\alpha_{{\rm ew}})$ electroweak ones, with the variations of the Higgs boson mass $m_{h}$ and $e^+e^-$ colliding energy $\sqrt{s}$. Both corrections may significantly decrease or increase the Born cross section. The numerical results show that the relative corrections from QCD to the process \eep may reach 34.8%, when $\sqrt{s}=800$ GeV and $m_h=200$ GeV, while those from electroweak can be -13.1%, -15.8% and -12.0%, at $\sqrt{s} = 800$ GeV, 1 TeV and 2 TeV respectively.