\section{Arrows and Labels} In addition to the actual lines of a Feynman diagram one commonly desires to include labels directly on the diagram, occasionally explanatory text or equations, and quite frequently arrows indicating the flow of momentum or some quantum number. These are accommodated quite easily in \FEYNMAN. \subsection{Arrows} The command for drawing arrows is \bs drawarrow. The syntax is similar to the \ddrawline\ command: \begin{verbatim} \drawarrow[] (<(x,y) co-ordinates of the arrow>) \end{verbatim} An arrowhead is produced at the specified (x,y) co-ordinates, generally at the end or middle of a line. The direction is one of the usual compass point directions: \begin{verbatim} \N \NE \E \SE \S \SW \W \NW \end{verbatim} If \bs LDIR or \bs LINEDIRECTION is used instead then the direction of the last drawn line will automatically be used (pre-supposing that a line has been drawn in the current picture). If the previous line was drawn by the \ddrawvertex\ command (see next chapter) then the {\it initially specified} vertex direction will be used. The {\em configuration} is one of the following: \begin{verbatim} \ATTIP \ATBASE \end{verbatim} These specify whether the co-ordinates which you've input refer to the position of the {\bf base} of the arrow or the {\bf tip} of the arrow. Arrows may be drawn boldly if \bs thicklines is in operation. The length of an arrow is given by the variable \bs arrowlength. When an arrow is attached to the end of a line the \bs particlelengthx,y are not altered (and neither is \bs gluonlengthx \etc) however the variables \bs{\it boxlengthx} and \bs{\it boxlengthy}, mentioned in subsection 2.10.2, assume a different meaning now. The {\it tip} of the arrow will always have co-ordinates (\bs~boxlengthx,\bs~boxlengthy), whether it is drawn with \bs ATTIP or \bs ATBASE. The following examples should illustrate these features. \begin{verbatim} \documentstyle [12pt]{article} \input FEYNMAN \begin {document} \bigphotons \centerline{ARROWS using FEYNMAN.TEX} \begin{picture}(10000,10000)(0,0) % PICTURE 1 \drawline\fermion[\NE\REG](0,0)[8000] \drawarrow[\LDIR\ATTIP](\pmidx,\pmidy) \drawline\fermion[\E\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\N\REG](\fermionfrontx,\fermionfronty)[2000] \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\S\REG](0,0)[2000] \drawarrow[\S\ATBASE](0,-2000) \drawarrow[\W\ATBASE](-2000,0) \end{picture} \hskip -0.4in \begin{picture}(10000,10000)(0,0) % PICTURE 2 \drawline\fermion[\SW\REG](0,0)[8000] \thicklines \drawarrow[\SW\ATTIP](\pbackx,\pbacky) \thinlines \drawline\fermion[\W\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\S\REG](\fermionfrontx,\fermionfronty)[2000] \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \drawarrow[\E\ATBASE](2000,0) \drawarrow[\N\ATBASE](0,2000) \end{picture} \hskip -0.4in \begin{picture}(10000,10000)(0,0) % PICTURE 3 \drawline\scalar[\SW\REG](0,0)[6] \drawarrow[\SW\ATTIP](\pbackx,\pbacky) \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \drawarrow[\E\ATBASE](2000,0) \drawarrow[\E\ATTIP](2000,0) \drawarrow[\N\ATBASE](0,2000) \drawarrow[\N\ATTIP](0,2000) \drawline\fermion[\W\REG](\scalarbackx,\scalarbacky)[2000] \drawline\fermion[\S\REG](\scalarbackx,\scalarbacky)[2000] \drawarrow[\E\ATTIP](\scalarbackx,\scalarbacky) \drawarrow[\N\ATTIP](\scalarbackx,\scalarbacky) \end{picture} \begin{picture}(10000,10000)(0,0) % PICTURE 4 \thicklines \drawline\fermion[\NW\REG](0,0)[8000] \drawline\fermion[\W\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\N\REG](\fermionfrontx,\fermionfronty)[2000] \drawarrow[\NW\ATBASE](-1000,1000) \drawarrow[\NW\ATBASE](-2000,2000) \drawarrow[\NW\ATBASE](-3000,3000) \drawarrow[\NW\ATTIP](-4000,4000) \drawarrow[\NW\ATTIP](-5000,5000) \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\S\REG](0,0)[2000] \end{picture} \begin{picture}(10000,10000)(0,0) % PICTURE 5 \drawline\photon[\E\REG](0,0)[8] \drawline\fermion[\E\REG](\pbackx,\pbacky)[200] \drawarrow[\E\ATBASE](\pbackx,\pbacky) \drawline\fermion[\SW\REG](0,0)[2000] \drawline\fermion[\NW\REG](0,0)[2000] \end{picture} \vskip 0.5in \begin{picture}(10000,10000)(0,0) % PICTURE 6 \drawline\gluon[\E\REG](0,0)[8] \drawarrow[\E\ATBASE](\pbackx,\pbacky) \drawline\fermion[\SW\REG](0,0)[2000] \drawline\fermion[\NW\REG](0,0)[2000] \end{picture} \hskip 0.42in \begin{picture}(10000,10000)(0,0) % PICTURE 7 \drawline\photon[\SE\REG](0,0)[8] \drawarrow[\E\ATBASE](\pmidx,\pmidy) \drawarrow[\E\ATBASE](\pbackx,\pbacky) \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \end{picture} \begin{picture}(10000,10000)(0,0) % PICTURE 8 \drawline\gluon[\SE\REG](0,0)[7] \drawarrow[\E\ATTIP](\pmidx,\pmidy) \drawarrow[\S\ATBASE](\pbackx,\pbacky) \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \end{picture} \end{verbatim} giving \centerline{ARROWS using FEYNMAN.TEX} \begin{picture}(10000,10000)(0,0) \drawline\fermion[\NE\REG](0,0)[8000] \drawarrow[\LDIR\ATTIP](\pmidx,\pmidy) \drawline\fermion[\E\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\N\REG](\fermionfrontx,\fermionfronty)[2000] \global\advance\fermionfrontx by 400 \global\advance\fermionfronty by 400 \put(\fermionfrontx,\fermionfronty){{\scriptsize 1}} \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\S\REG](0,0)[2000] \drawarrow[\S\ATBASE](0,-2000) \drawarrow[\W\ATBASE](-2000,0) \end{picture} \hskip -0.4in \begin{picture}(10000,10000)(0,0) \drawline\fermion[\SW\REG](0,0)[8000] \thicklines \drawarrow[\SW\ATTIP](\pbackx,\pbacky) \thinlines \drawline\fermion[\W\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\S\REG](\fermionfrontx,\fermionfronty)[2000] \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \global\advance\fermionfrontx by 400 \global\advance\fermionfronty by 400 \put(\fermionfrontx,\fermionfronty){{\scriptsize 2}} \drawarrow[\E\ATBASE](2000,0) \drawarrow[\N\ATBASE](0,2000) \end{picture} \hskip -0.4in \begin{picture}(10000,10000)(0,0) \drawline\scalar[\SW\REG](0,0)[6] \drawarrow[\SW\ATTIP](\pbackx,\pbacky) \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \global\advance\fermionfrontx by 400 \global\advance\fermionfronty by 400 \put(\fermionfrontx,\fermionfronty){{\scriptsize 3}} \drawarrow[\E\ATBASE](2000,0) \drawarrow[\E\ATTIP](2000,0) \drawarrow[\N\ATBASE](0,2000) \drawarrow[\N\ATTIP](0,2000) \drawline\fermion[\W\REG](\scalarbackx,\scalarbacky)[2000] \drawline\fermion[\S\REG](\scalarbackx,\scalarbacky)[2000] \drawarrow[\E\ATTIP](\scalarbackx,\scalarbacky) \drawarrow[\N\ATTIP](\scalarbackx,\scalarbacky) \end{picture} \begin{picture}(10000,10000)(0,0) \thicklines \drawline\fermion[\NW\REG](0,0)[8000] \global\advance\pmidy by 500 \put(\pmidx,\pmidy){{\scriptsize 4}} \drawline\fermion[\W\REG](\fermionbackx,\fermionbacky)[2000] \drawline\fermion[\N\REG](\fermionfrontx,\fermionfronty)[2000] \drawarrow[\NW\ATBASE](-1000,1000) \drawarrow[\NW\ATBASE](-2000,2000) \drawarrow[\NW\ATBASE](-3000,3000) \drawarrow[\NW\ATTIP](-4000,4000) \drawarrow[\NW\ATTIP](-5000,5000) \drawline\fermion[\E\REG](0,0)[2000] \drawline\fermion[\S\REG](0,0)[2000] \end{picture} \begin{picture}(10000,10000)(0,0) \drawline\photon[\E\REG](0,0)[8] \global\advance\pmidx by -600 \global\advance\pmidy by 500 \put(\pmidx,\pmidy){{\scriptsize 5}} \drawline\fermion[\E\REG](\pbackx,\pbacky)[200] \drawarrow[\E\ATBASE](\pbackx,\pbacky) \drawline\fermion[\SW\REG](0,0)[2000] \drawline\fermion[\NW\REG](0,0)[2000] \end{picture} \vskip 0.5in \begin{picture}(10000,10000)(0,0) \drawline\gluon[\E\REG](0,0)[8] \global\advance\pmidx by -200 \global\advance\pmidy by -2000 \put(\pmidx,\pmidy){{\scriptsize 6}} \drawarrow[\E\ATBASE](\pbackx,\pbacky) \drawline\fermion[\SW\REG](0,0)[2000] \drawline\fermion[\NW\REG](0,0)[2000] \end{picture} \hskip 0.42in \begin{picture}(10000,10000)(0,0) \drawline\photon[\SE\REG](0,0)[8] \drawarrow[\E\ATBASE](\pmidx,\pmidy) \drawarrow[\E\ATBASE](\pbackx,\pbacky) \global\advance\pmidx by -200 \global\advance\pmidy by 500 \put(\pmidx,\pmidy){{\scriptsize 7}} \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \end{picture} \begin{picture}(10000,10000)(0,0) \drawline\gluon[\SE\REG](0,0)[7] \drawarrow[\E\ATTIP](\pmidx,\pmidy) \drawarrow[\S\ATBASE](\pbackx,\pbacky) \global\advance\pmidx by 100 \global\advance\pmidy by 800 \put(\pmidx,\pmidy){{\scriptsize 8}} \drawline\fermion[\W\REG](0,0)[2000] \drawline\fermion[\N\REG](0,0)[2000] \end{picture} \hskip 0.41in