$$ T_{i_ai_b} = \frac{\hbar (-1)^{i_a-i_b}}{2m_w \Delta w^2} \left\{ \begin{array}{ll} \dfrac{\pi^2}{3}, & i_a = i_b \\ \dfrac{2}{(i_a-i_b)^2}, & i_a \neq i_b \end{array} \right\} $$$$ T_{i_ai_b} = \frac{\hbar^2 (-1)^{i_a-i_b}}{2m_w \Delta w^2} \left\{ \begin{array}{ll} \dfrac{\pi^2}{3}, & i_a = i_b \\ \dfrac{2}{(i_a-i_b)^2}, & i_a \neq i_b \end{array} \right\} $$
EDIT 2:
Correction of LaTeX code: should be $\hbar^2$ in definition of T, not $\hbar$ as previously written.
