\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}
(A_{l,\mu})^{\alpha\beta}:= \langle\psi_{l}^\alpha(\lambda)|
\,{\partial}/{\partial\lambda^\mu}\,
|\psi_{l}^\beta(\lambda)\rangle
\label{conn}
\end{equation*}
\end{document}