how to add single-sided brackets in latex

to produce the above equation, use the following code:

\begin{split}
\arg\max_\Theta\left[\sum_zP(\mathcal{G}|\mathcal{D},\mathcal{S})
P(\mathcal{G}|\mathcal{S},\Theta_n)\log{P(\mathcal{D}|\mathcal{G},
\mathcal{S},\Theta)}\right. \ +
\left.\sum_zP(\mathcal{G}|\mathcal{D},\mathcal{S})P(\mathcal{G}|
\mathcal{S},\Theta_n)\log{P(\mathcal{D}|\mathcal{G},\mathcal{S},\Theta)}\right]
\end{split}

note that to produce the single-sided brackets, you need to add empty \left and \right brackets, which can be done by inserting periods following the \left or \right statement.