Drawing a scattering Feynman diagram with TikZ

Question

I am trying to produce a scattering diagram with TikZ but I have become stuck.

The Desired Structure

I am trying to achieve this layout of lines, including their arrow directions. In my diagram.

Minimum Working Example

\documentclass[11pt]{article}
\usepackage[latin1]{inputenc}
\usepackage{tikz}
\usetikzlibrary{trees}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}

\tikzset{
photon/.style={decorate, decoration={snake}, draw=red},
particle/.style={draw=blue, postaction={decorate},
    decoration={markings,mark=at position .5 with {\arrow[draw=blue]{>}}}},
antiparticle/.style={draw=blue, postaction={decorate},
    decoration={markings,mark=at position .5 with {\arrow[draw=blue]{<}}}},
gluon/.style={decorate, draw=black,
    decoration={coil,amplitude=4pt, segment length=5pt}}
 }

\begin{tikzpicture}[
    thick,
    % Set the overall layout of the tree
    level/.style={level distance=1.5cm},
    level 2/.style={sibling distance=3.5cm},
]
\coordinate
    child[grow=down]{
        edge from parent [antiparticle]
        child {
        node{$E$}
        edge from parent [particle]
        }
        child {
         node{$D$}
         edge from parent [gluon]
        }
        node [above=3pt] {$C$}
     }
    % I have to insert a dummy child to get the tree to grow
    % correctly to the right.
    child[grow=right, level distance=0pt] {
        child {
        node{$A$}
        edge from parent [gluon]
        }
        child { 
        node{$B$}
        edge from parent [particle]               
        }
    };
\end{tikzpicture}

\end{document}

Output

So far, I have the basic structure, except one of my lines is 'wandering'. The one that's labelled $A$ should be 'reflected' from where it is by 180 degrees.

Edit

Using @GonzaloMedina's approach, and with his helpful suggestion to the TikZ lirary, I found I can get the following diagram, which is very close to what I wanted:

\begin{document}
\tikzset{
particle/.style={thick,draw=blue, postaction={decorate},
    decoration={markings,mark=at position .5 with {\arrow[blue]{triangle 45}}}},
gluon/.style={decorate, draw=black,
    decoration={coil,aspect=0}}
 }
\tikzset{
particle/.style={thin,draw=blue, postaction={decorate},
decoration={markings,mark=at position .5 with {\arrow[blue]{stealth}}}},
gluon/.style={decorate, draw=black, decoration={snake=coil}}
}

\begin{tikzpicture}[node distance=1cm and 1.5cm]
\coordinate[label=left:$G$] (e1);
\coordinate[below right=of e1] (aux1);
\coordinate[above right=of aux1,label=right:$N$] (e2);
\coordinate[below=1.25cm of aux1] (aux2);
\coordinate[below left=of aux2,label=left:$N$] (e3);
\coordinate[below right=of aux2,label=right:$G$] (e4);

\draw[gluon] (e1) -- (aux1);
\draw[particle] (aux1) -- (e2);
\draw[particle] (e3) -- (aux2);
\draw[gluon] (aux2) -- (e4);
\draw[particle] (aux2) -- node[label=right:$N$] {} (aux1);
\end{tikzpicture}
\end{document}

I looked in the TikZ manual (on page 95) and found how to make a coil (like a spring), but it didn't seem to work.

Answer 1

One possibility: instead of a tree, I just used some coordinates and decorated paths; I used the triangle 45 arrow tip from the arrows library, changed the gluon style to use decoration={coil,aspect=0}, and suppressed parts of the original code not relevant here:

\documentclass[11pt]{article}
\usepackage{tikz}
\usetikzlibrary{positioning,arrows}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}

\tikzset{
particle/.style={thick,draw=blue, postaction={decorate},
    decoration={markings,mark=at position .5 with {\arrow[blue]{triangle 45}}}},
gluon/.style={decorate, draw=black,
    decoration={coil,aspect=0}}
 }

\begin{tikzpicture}[node distance=1cm and 1.5cm]
\coordinate[label=left:$e^{-}$] (e1);
\coordinate[below right=of e1] (aux1);
\coordinate[above right=of aux1,label=right:$e^{-}$] (e2);
\coordinate[below=1.25cm of aux1] (aux2);
\coordinate[below left=of aux2,label=left:$e^{-}$] (e3);
\coordinate[below right=of aux2,label=right:$e^{-}$] (e4);

\draw[particle] (e1) -- (aux1);
\draw[particle] (aux1) -- (e2);
\draw[particle] (e3) -- (aux2);
\draw[particle] (aux2) -- (e4);
\draw[gluon] (aux1) -- node[label=right:$\gamma$] {} (aux2);
\end{tikzpicture}
\end{document}

After an edit to the question, here's some new code with the required coil decoration:

\documentclass[11pt]{article}
\usepackage{tikz}
\usetikzlibrary{positioning,arrows}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}


\begin{document}
\tikzset{
particle/.style={thick,draw=blue, postaction={decorate},
    decoration={markings,mark=at position .5 with {\arrow[blue]{triangle 45}}}},
gluon/.style={decorate, draw=black,
    decoration={coil,aspect=0.3,segment length=3pt,amplitude=3pt}}
 }

\begin{tikzpicture}[node distance=1cm and 1.5cm]
\coordinate[label=left:$G$] (e1);
\coordinate[below right=of e1] (aux1);
\coordinate[above right=of aux1,label=right:$N$] (e2);
\coordinate[below=1.25cm of aux1] (aux2);
\coordinate[below left=of aux2,label=left:$N$] (e3);
\coordinate[below right=of aux2,label=right:$G$] (e4);

\draw[gluon] (e1) -- (aux1);
\draw[particle] (aux1) -- (e2);
\draw[particle] (e3) -- (aux2);
\draw[gluon] (aux2) -- (e4);
\draw[particle] (aux2) -- node[label=right:$N$] {} (aux1);
\end{tikzpicture}
\end{document}

Answer 2

You can also use the feynMP package to create Feynman diagrams. It uses metapost instead of tikz, but provides a nice interface for creating different types of Feynman diagrams. For example:

\documentclass{article}
\usepackage{feynmp}
\DeclareGraphicsRule{*}{mps}{*}{}

\begin{document}
\unitlength = 1mm
\begin{fmffile}{gluon}
\begin{fmfgraph*}(40,30) 
  \fmfleft{i1,i2} 
  \fmflabel{$e^{-}$}{i1}
  \fmflabel{$e^{-}$}{i2}
  \fmfright{o1,o2}
  \fmflabel{$e^{-}$}{o1}
  \fmflabel{$e^{-}$}{o2}
  \fmf{fermion, fore=blue}{i1,v1,o1} 
  \fmf{fermion, fore=blue}{i2,v2,o2}
  \fmf{photon,label=$\gamma$}{v1,v2} 
  \fmfdot{v1,v2}
\end{fmfgraph*}
\end{fmffile}
\write18{mpost gluon}
\end{document}

Run this twice with pdflatex --shell-escape filename, and you will get

Answer 3

These diagrams are very easy to produce with the new tikz-feynman package (see also the project page), based on this answer. The only requirement for using automatic positioning of the vertices is to compile the document with lualatex:

\documentclass[tikz]{standalone}
\usepackage[compat=1.1.0]{tikz-feynman}
\begin{document}
\feynmandiagram [vertical=b to a] {
  i1 [particle=\(\textup{e}^{-}\)] -- [fermion] a -- [fermion] i2 [particle=\(\textup{e}^{-}\)],
  a -- [photon,edge label'=\(\gamma\)] b,
  f1 [particle=\(\textup{e}^{-}\)] -- [fermion] b -- [fermion] f2 [particle=\(\textup{e}^{-}\)],
};

\tikzfeynmanset{
  every fermion={draw=blue},
}
\feynmandiagram [vertical=b to a] {
  i1 [particle=\(N\)] -- [fermion] a,
  i2 [particle=\(G\)] -- [photon] a,
  a  -- [fermion,edge label'=\(N\)] b,
  b  -- [photon] f1 [particle=\(G\)],
  b  -- [fermion] f2 [particle=\(N\)],
};
\end{document}

Answer 4

Here is my take on this. I think it produces beautiful output and doesn't require running any special programs like feynmp. Drawback: you have to put in the nodes manually, but that's very managable imho. Bonus: it retains full flexibility for using any kind of tikz decorations and so on while at the same time making it easy to use due to the tree approach.

\documentclass{standalone}

\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{trees}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}

% Define styles for the different kind of edges in a Feynman diagram
\tikzset{
    gageboson/.style={decorate,decoration={snake},draw=tud9a},
    electronin/.style={draw=tud1a,postaction={decorate},decoration={markings,mark=at position .55 with {\arrow[draw=tud1a]{<}}}},
    electronout/.style={draw=tud1a,postaction={decorate},decoration={markings,mark=at position .55 with {\arrow[draw=tud1a]{>}}}},
    gluon/.style={decorate,draw=magenta,decoration={coil,amplitude=4pt,segment length=5pt}}
}

\begin{tikzpicture}[thick,
        % Set the overall layout of the tree
        level/.style={level distance=1.2cm},
        level 2/.style={sibling distance=2.6cm},
        level 3/.style={sibling distance=2cm}
    ]
    \coordinate
        child[grow=up]{
            child {
                node {$k^{'}_{1}$}
                edge from parent [electronout]
            }
            child {
                node {$k_1$}
                edge from parent [electronin]
            }
            edge from parent [gageboson] node [right=3pt] {$q$}
        }
        child[grow=down,level distance=0pt]{
            child {
                node {$k_{2}$}
                edge from parent [electronin]
            }
            child {
                node {$k^{'}_2$}
                edge from parent [electronout]
            }
        };
    \fill[black] (0,0) circle (.05cm);
    \fill[black] (0,1.2cm) circle (.05cm);
\end{tikzpicture}

\end{document}

Yields:

However, when you look closely, the wriggly line of the phonon is not perfect. Anybody know how to get rid of that linear part?

In the particular case asked above, the code would be:

\documentclass{standalone}

\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{trees}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}

% Define styles for the different kind of edges in a Feynman diagram
\tikzset{
    gageboson/.style={decorate,decoration={snake},draw=black},
    electronin/.style={draw=tud1a,postaction={decorate},decoration={markings,mark=at position .55 with {\arrow[draw=red]{<}}}},
    electronout/.style={draw=tud1a,postaction={decorate},decoration={markings,mark=at position .55 with {\arrow[draw=red]{>}}}},
    gluon/.style={decorate,draw=magenta,decoration={coil,amplitude=4pt,segment length=5pt}}
}

\begin{tikzpicture}[
        thick,
        % Set the overall layout of the tree
        level/.style={level distance=1.5cm},
        level 2/.style={sibling distance=2.6cm},
        level 3/.style={sibling distance=2cm}
    ]
    \coordinate
        child[grow=up]{
            child {
                node {$N$}
                edge from parent [electronout]
            }
            child {
                node {$G$}
                edge from parent [gageboson]
            }
            edge from parent [electronout] node [right=3pt] {$N$}
        }
        child[grow=down,level distance=0pt]{
            child {
                node {$N$}
                edge from parent [electronin]
            }
            child {
                node {$G$}
                edge from parent [gageboson]
            }
        };
    \fill[black] (0,0) circle (.05cm);
    \fill[black] (0,1.5cm) circle (.05cm);
\end{tikzpicture}

\end{document}

and results in this