%    FEYNMANDOC2C:  CHAPTER 2 PART C OF FEYNMANDOC.TEX  \include d there.
%
\section{Gluons}
\subsection{Anatomy of a Gluon}

A gluon consists of connected loops.  As in the case of the photon line,
the length of a single loop varies between styles and configurations.
The syntax for creating a gluon with the \ddrawline\ command is:
\begin{verbatim}

\drawline\gluon[<gluon direction><gluon style>]
       <(x,y), the co-ordinates of the beginning of the gluon>[<number of loops>]

\end{verbatim}
The styles currently available for gluons are:

\begin{verbatim}

                                 \REG
                                 \FLIPPED
                                 \CURLY
                                 \FLIPPEDCURLY
                                 \FLAT
                                 \FLIPPEDFLAT
                                 \CENTRAL
                                 \FLIPPEDCENTRAL
                                 \SQUASHEDGLUON

\end{verbatim}

The \bs REG and \bs FLIPPED styles are available in all orientations.
The others are available only in the following directions:
\begin{verbatim}

                \CURLY:           \N, \S, \E, \W   
                \FLIPPEDCURLY:    \N, \S, \E, \W   
                \CENTRAL:         \N, \S, \E, \W   
                \FLIPPEDCENTRAL:  \N, \S, \E, \W   
                \FLAT:            \E, \W
                \FLIPPEDFLAT:     \E, \W
                \SQUASHEDGLUON:   \E

\end{verbatim}
The differences in style are illustrated in the next subsection.
The \bs THICKLINES, \bs THINLINES,
\bs thicklines and \bs thinlines options are available in all
orientations and styles.

\medskip
The parameters returned by \ddrawline\bs gluon are analogous
to those returned after drawing photons, fermions and scalars:

\begin{verbatim}

\gluonfrontx,\gluonfronty:         The (x,y) co-ordinates of the front of the line.
\gluonbackx,\gluonbacky:           The (x,y) co-ordinates of the back of the line.
\gluonlengthx,\gluonlengthy:       The (x,y) extent of the line.
\gluoncount                        The number of gluons printed thus far.
\particlefrontx,\particlefronty:   The (x,y) co-ords of the front of the line.
\particlemidx,\particlemidy:       The (x,y) co-ordinates of the middle of the line.
\particlebackx,\particlebacky:     The (x,y) co-ordinates of the back of the line.
\particlelengthx,\particlelengthy: The (x,y) extent of the line.

\end{verbatim}
\newpage
%
\subsection{Examples and Details}

The different styles of gluon are:
\vskip -0.5in  \hskip 0.4in
\begin{picture}(40000,8000)(0,10000)
\drawline\gluon[\S\REG](0,8000)[6]   
\put(-1000,10000){{\tiny \bs REG}}
\drawline\gluon[\S\FLIPPED](6000,8000)[6]   
\put(4300,10000){{\tiny \bs FLIPPED}}
\drawline\gluon[\S\CURLY](12000,8000)[6]   
\put(10500,10000){{\tiny \bs CURLY}}
\drawline\gluon[\S\FLIPPEDCURLY](18000,8000)[6]   
\put(15000,10000){{\tiny \bs FLIPPEDCURLY}}
\drawline\gluon[\S\CENTRAL](24000,8000)[6]   
\put(22200,10000){{\tiny \bs CENTRAL}}
\drawline\gluon[\S\FLIPPEDCENTRAL](30000,8000)[6]   
\put(26500,10000){{\tiny \bs FLIPPEDCENTRAL}}
\drawline\gluon[\E\FLAT](-1000,-500)[6]   
\put(1500,-2500){{\tiny \bs FLAT}}
\drawline\gluon[\E\FLIPPEDFLAT](11200,-500)[6]   
\put(12100,-2500){{\tiny \bs FLIPPEDFLAT}}
\drawline\gluon[\E\SQUASHEDGLUON](23500,-500)[6]   
\put(23500,-2500){{\tiny \bs SQUASHEDGLUON}}
%\drawline\gluon[\E\FLAT](5000,-500)[6]   
%\put(7000,-2500){{\tiny \bs FLAT}}
%\drawline\gluon[\E\SQUASHEDGLUON](20000,-500)[6]   
%\put(20000,-2500){{\tiny \bs SQUASHEDGLUON}}

\end{picture}
\vskip 2.5in
The different directions may be illustrated by the following file:

\begin{verbatim}

% EXAMPLE OF USING FEYNMAN TO DRAW gluon DIAGRAMS IN TEX.
\documentstyle [11pt]{article}
\input FEYNMAN
\begin {document}
\centerline{GLUONBURST using FEYNMAN}
\vskip 0.75in
\hskip 1.5in
\begin{picture}(20000,20000)(-10000,-10000)
\put(0,0){\circle*{1500}}
\drawline\gluon[\N\CENTRAL](0,0)[10]
\drawline\gluon[\NE\REG](0,0)[8]
\drawline\gluon[\E\CENTRAL](0,0)[10]
\drawline\gluon[\SE\REG](0,0)[8]
\drawline\gluon[\S\CENTRAL](0,0)[10]
\drawline\gluon[\SW\REG](0,0)[8]
\drawline\gluon[\W\CENTRAL](0,0)[10]
\drawline\gluon[\NW\REG](0,0)[8]
\end{picture}

\end{verbatim}
Which produces: