Dashed line in equation

Question

What I want:

What I have:

with this code:

\documentclass[11pt, titlepage]{report}
\begin{document}

\begin{equation} \label{eq:quark1}
   \left( \begin{array}{c}
u \\ 
c  \\
t \end{array} \right),  \left( \begin{array}{c}
d \\
s  \\
b \end{array} \right) \hphantom{iiiii} \begin{array}{c}
\textnormal{1\textsuperscript{st}} \\
\textnormal{2\textsuperscript{nd}}  \\
\textnormal{3\textsuperscript{rd}} \end{array} 
\end{equation}

\end{document}

I am trying to use \hdashline[2pt/2pt] which I saw in this post, but it doesn't work (undefined control sequence...)

Answer 1

Here I \stackon your system of arrays a \Centerstack of three dashed lines (with a -3pt shift).

\documentclass[11pt, titlepage]{report}
\usepackage{stackengine}
\stackMath
% DASHED LINE OF SPECIFIED LENGTH
% From morsburg at http://tex.stackexchange.com/questions/12537/
% how-can-i-make-a-horizontal-dashed-line/12553#12553
\def\dashfill{\cleaders\hbox to .5em{\rule{.4ex}{.4pt}}\hfill}
\newcommand\dashline[1]{\hbox to #1{\dashfill\hfil}}

\begin{document}
\begin{equation} \label{eq:quark1}
\renewcommand\stacktype{L}
\stackon[-3pt]{%
   \left( \begin{array}{c}
u \\ 
c  \\
t \end{array} \right),  \left( \begin{array}{c}
d \\
s  \\
b \end{array} \right) \hphantom{iiiii} \begin{array}{c}
\textnormal{1\textsuperscript{st}} \\
\textnormal{2\textsuperscript{nd}}  \\
\textnormal{3\textsuperscript{rd}} \end{array}
}{
\Centerstack{\dashline{1.7in} \dashline{1.7in} \dashline{1.7in}}
}
\end{equation}

\end{document}