= -\frac{C_{t1}}{\Lambda^2}
 \frac{v}{\sqrt2} \bar u_t v_t, \\
{\mathcal M}_H^{\omega^- \omega^+ \to t \bar t} 
(2 \pi)^3 \sqrt{2p^0} \sqrt{2{p'}^0} & = \frac{m_H^2/v}{\hat{s}-m_H^2+i
 m_H \Gamma_H}
\frac{y_t^{\rm eff}(\hat{s},\Lambda)}{\sqrt{2}}
 \bar u_t   v_t, \\
{\mathcal M}_\gamma^{\omega^- \omega^+ \to t \bar t} 
(2 \pi)^3 \sqrt{2p^0} \sqrt{2{p'}^0} & = - \frac{Q_t e^2}{\hat{s}}  \bar
 u_t i P\!\!\!\!/\, v_t, \\
{\mathcal M}_Z^{\omega^- \omega^+ \to t \bar t} 
(2 \pi)^3 \sqrt{2p^0} \sqrt{2{p'}^0} &
 = - \frac{g_Z^2 (V_t + A_t)}{4 (\hat{s}-m_Z^2)} \bar u_t  \left( i P\!\!\!\!/\,
 (V_t + A_t \gamma_5)  + \frac{C_{Dt}}{\Lambda^2} \frac{v}{2\sqrt2}
 K\cdot P \right) v_t, \\
{\mathcal M}_b^{\omega^- \omega^+ \to t \bar t} 
(2 \pi)^3 \sqrt{2p^0} \sqrt{2{p'}^0} & = - \frac{1}{\hat{u}-m_b^2}
 \left(y_t^{\rm SM} - \frac{C_{Dt}}{\Lambda^2} p\cdot {k'}
 \right)^2
 \bar u_t P_L  i (p\!\!\!\!/\,-k'\!\!\!\!/\,) v_t, \end{aligned}$$ where momenta $p$ ($p'$) and $k$ ($k'$) are defined in a similar way to the case of $W^-W^+\to t \bar t$. The invariant amplitude is obtained as $$\begin{aligned}
    {\cal M}^{\omega\omega\to tt} = 
{\cal M}^{\omega\omega\to tt}_{\times} 
+{\cal M}^{\omega\omega\to tt}_H
+{\cal M}^{\omega\omega\to tt}_\gamma
+{\cal M}^{\omega\omega\to tt}_Z
+{\cal M}^{\omega\omega\to tt}_b. \end{aligned}$$

The numerical results for the subprocess $W_\lambda^-W_{\bar \lambda}^+\to t \bar t$ in the model with the dimension-six operators ${\cal O}_{t1}$ and ${\cal O}_{Dt}$ are shown as solid curves in Figs. \[fig:WW-tt-ct1\](a) and \[fig:WW-tt-ct1\](b) and in Figs. 