A general result concerning gluon styles is that the \bs CURLY (\bs FLIPPEDCURLY) and the \bs CENTRAL (\bs FLIPPEDCENTRAL) configurations are frequently more appealing than the \bs REG (\bs FLIPPED) configuration if both diagonal and non-diagonal gluons appear in the same diagram. The reason is that slanted (eg. NW) gluons may only be drawn in a \bs CENTRALGLUON sort of style (but still called \bs REG) and the \bs CURLY style is also very similar to this from a spacing and size viewpoint. Another important point is that gluons are by far the most {\em expensive} sort of lines to draw from the viewpoint of \TeX's internal memory (independent of the memory of the driving system). For this reason you will quickly discover that diagrams involving a great many gluons tend to run out of \TeX\ capacity. One way to alleviate the problem is to use \LaTeX's `\bs include' facility which allows you to divide up a long program into a series of small ones connected by {\em auxiliary} files which are automatically produced when \LaTeX\ is run. Dozens of photonic, scalar and fermionic diagrams may be constructed for the same memory usage of a single hadronic diagram. A number a further features exist which will be mentioned here and elaborated on in subsequent chapters. Thus far no multi-gluon vertices have been drawn. Using the techniques presented here it is obvious how this may be done - draw a gluon at (\bs gluonbackx,\bs gluonbacky), attaching it at the rear of the last gluon. The results are not always \ae sthetically appealing so a number a pre-drawn vertices are available. This is the subject of chapter 3. A further feature has to do with attaching gluons end-to-end. This may not seem necessary but is often desirable (see the exercise below). The problem is illustrated by the following file: \begin{verbatim} \begin{picture}(25000,7000) \drawline\gluon[\E\REG](0,3000)[4] \drawline\gluon[\E\REG](\pbackx,\pbacky)[4] \drawline\gluon[\E\CENTRAL](15000,3000)[4] \drawline\gluon[\E\CENTRAL](\pbackx,\pbacky)[4] \end{picture} \end{verbatim} giving us: \begin{picture}(25000,7000) \drawline\gluon[\E\REG](0,4000)[4] \drawline\gluon[\E\REG](\pbackx,\pbacky)[4] \drawline\gluon[\E\CENTRAL](15000,4000)[4] \drawline\gluon[\E\CENTRAL](\pbackx,\pbacky)[4] \end{picture} For gluons in the N,S, E and W directions \bs REG, \bs CURLY, \bs FLAT and \bs SQUASHED configurations may be attached end-to-end trivially. For \bs CENTRAL gluons and all gluons in the NW, NE, SE and SW directions the connection is imperfect. The \verb@\gluonlink@ command, discussed in chapter four, alleviates this: \begin{verbatim} \begin{picture}(10000,5000) \drawline\gluon[\E\CENTRAL](0,3000)[4]\gluonlink \drawline\gluon[\E\CENTRAL](\pbackx,\pbacky)[4] \end{picture} \end{verbatim} \begin{picture}(10000,5000) \drawline\gluon[\E\CENTRAL](0,3000)[4]\gluonlink \drawline\gluon[\E\CENTRAL](\pbackx,\pbacky)[4] \end{picture} \vskip 0.15in The {\em stemmed} option demonstrated for photons is also available for gluons and is of significantly more interest, especially for those of the \bs CENTRAL variety: \vskip 0.2in \hskip 1.25in \begin{picture}(25000,10000) \drawline\gluon[\E\CENTRAL](0,7000)[6] \advance \gluonfrontx by -800 \put(\gluonfrontx,2000){UNSTEMMED} \drawline\fermion[\NW\REG](\pfrontx,\pfronty)[2000] \drawline\fermion[\SW\REG](\pfrontx,\pfronty)[2000] \drawline\fermion[\NE\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2000] \stemmed\drawline\gluon[\E\CENTRAL](13000,7000)[6] \gluonbacky=\pbacky \gluonbackx=\pbackx \advance \gluonfrontx by 400 \put(\gluonfrontx,2000){STEMMED} \drawline\fermion[\NW\REG](\pfrontx,\pfronty)[2000] \drawline\fermion[\SW\REG](\pfrontx,\pfronty)[2000] \drawline\fermion[\NE\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2000] \end{picture} \vskip 0.34in The chief advantage of \bs CENTRAL gluons is that their endpoints are approximately on the axis along which the line is being drawn. This may be artificially achieved for other styles using the \bs gluoncap command. The {\it capped} option is unique to gluons. It is employed to make gluon lines of a non-central variety (\ie\ those which do not terminate near the axis of the gluon line) appear centralized. An example is: \vskip 0.2in \hskip 0.71in \begin{picture}(25000,10000) \THICKLINES \put(4000,7000){\circle{3000}} \drawline\gluon[\E\REG](5400,7000)[4] \drawline\fermion[\NE\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2000] \drawline\gluon[\W\FLIPPED](2600,7000)[4] \drawline\fermion[\NW\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SW\REG](\gluonbackx,\gluonbacky)[2000] \advance \gluonfrontx by -1500 \put(\gluonfrontx,2000){UNCAPPED} %\put(24000,7000){\circle{3000}} %\drawline\gluon[\E\REG](25500,7000)[4]\gluoncap %\drawline\fermion[\NE\REG](\gluonbackx,\gluonbacky)[2000] %\drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2000] %\drawline\gluon[\W\FLIPPED](22500,7000)[4]\gluoncap %\drawline\fermion[\NW\REG](\gluonbackx,\gluonbacky)[2000] %\drawline\fermion[\SW\REG](\gluonbackx,\gluonbacky)[2000] %\advance \gluonfrontx by -900 %\put(\gluonfrontx,2000){CAPPED} \put(24000,7000){\circle{3000}} \startphantom \drawline\gluon[\E\REG](0,0)[2]\gluoncap \stopphantom \pbackx=22600 \pbacky=7000 \multiply \plengthx by -1 \multiply \plengthy by -1 \advance \pbackx by \plengthx \advance \pbacky by \plengthy \drawline\gluon[\E\REG](\pbackx,\pbacky)[2]\gluoncap %\advance\gluonfrontx by 75 \drawline\gluon[\W\FLIPPED](\gluonfrontx,\gluonfronty)[2]\gluoncap \drawline\fermion[\NW\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SW\REG](\gluonbackx,\gluonbacky)[2000] \gluonbackx=25400 \gluonbacky=7000 \multiply \gluonlengthx by -1 \multiply \gluonlengthy by -1 \advance \gluonbackx by \gluonlengthx \advance \gluonbacky by \gluonlengthy \drawline\gluon[\W\FLIPPED](\gluonbackx,\gluonbacky)[2]\gluoncap %\advance\gluonfrontx by -75 \drawline\gluon[\E\REG](\gluonfrontx,\gluonfronty)[2]\gluoncap \drawline\fermion[\NE\REG](\gluonbackx,\gluonbacky)[2000] \drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2000] \advance \gluonfrontx by -6800 \put(\gluonfrontx,2000){CAPPED} \THINLINES \end{picture} \vskip 0.2in There are a number of subtleties involved with the above features which is why their discussion is being postponed. Finally a primitive \bs drawloop\footnote{currently only available for gluons} command allows a gluon loop to be drawn. These are also discussed in chapter four. We conclude with the following exercises. First draw the following which uses \bs REG style gluons: \begin{picture}(20000,20000) \thinlines \drawline\gluon[\E\REG](18000,18000)[4] \drawline\fermion[\S\REG](\pfrontx,\pfronty)[\gluonlengthx] \thicklines \drawline\gluon[\E\REG](\gluonbackx,\gluonbacky)[4] \drawline\fermion[\S\REG](\pbackx,\pbacky)[\gluonlengthx] \thinlines \drawline\fermion[\S\REG](\pbackx,\pbacky)[\gluonlengthx] \drawline\gluon[\W\REG](\fermionbackx,\fermionbacky)[4] \thicklines \drawline\gluon[\W\REG](\gluonbackx,\gluonbacky)[4] \drawline\fermion[\N\REG](\pbackx,\pbacky)[\fermionlength] \end{picture} \vskip -0.15in How would you draw this using \bs CENTRAL gluons {\it without} invoking the \bs gluonlink command? % Answer: each gluon should be drawn in 3 overlapping pieces: %\drawline\gluon[\E\CENTRAL](0,0)[5] %\drawline\gluon[\E\CENTRAL](0,0)[4] %\thicklines\drawline\gluon[\E\CENTRAL](0,0)[4]