# Wick Contractions aren't displaying properly

My Wick contractions aren't displaying properly: the ones on the left are fine but the ones on the right have the contraction at a very low height

\documentclass[amsmath,amssymb,12pt,eqsecnum]{revtex4}
\usepackage[a4paper]{geometry}
\usepackage{slashed}
\usepackage{gensymb}
\usepackage{simplewick}
\usepackage{feynmp-auto}
\usepackage[pdftex]{graphicx}
\begin{document}

\begin{eqnarray}
\contraction{}{\psi}{|p}{,} \psi |p,s \rangle = u^s (p) &\quad& \langle
p \contraction{}{,}{s|}{\bar{\psi}} ,s|\bar{\psi}
= \bar{u}^s (p) \\ \nonumber
\contraction{}{\bar{\psi}}{|k}{,} \bar{\psi}|k,s \rangle = \bar{v}^s (k)
&\quad& \langle k \contraction{}{,}{s|}{\psi} ,s| \psi
= v^s (k) \nonumber
\end{eqnarray}

\end{document}

• Never use eqnarray; in this case the align* environment is what you want. – egreg Dec 28 '14 at 10:38

simplewick uses the height of the character in the second argument to raise the contraction symbol to its appropriate height. Unfortunately , is a little too small so you have to add \vphantom{...} to raise the symbol a more reasonable height.

\documentclass{article}
\usepackage{simplewick}
\begin{document}
\begin{eqnarray}
\contraction{}{\psi}{|p}{,} \psi |p,s \rangle = u^s (p) &\quad& \langle
p \contraction{}{\vphantom{\bar\psi},}{s|}{\bar{\psi}} ,s|\bar{\psi}
= \bar{u}^s (p) \\ \nonumber
\contraction{}{\bar{\psi}}{|k}{,} \bar{\psi}|k,s \rangle = \bar{v}^s (k)
&\quad& \langle k \contraction{}{\vphantom{\psi},}{s|}{\psi} ,s| \psi
= v^s (k) \nonumber
\end{eqnarray}
\end{document}