1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
|
\chapter{Drawing Lines}
\section{The \ddrawline\ Command}
The principal command for drawing a particle line in \FEYNMAN\ is
via the {\it \ddrawline}\ statement. The syntax is:\\
%\ddrawline$<$particle type$>$[$<$particle direction$> <$configuration$>$]
%$<$co-ordinates of the beginning of the line of form $(x,y)>$[$<$length$>$\\
\begin{verbatim}
\drawline<particle type>[<particle direction><configuration>]
<(x,y), the co-ordinates of the beginning of the line>[<length>]
\end{verbatim}
where it is understood that the triangular brackets do not appear in the
syntax but their contents describe what goes in that position.
An example would be:
\begin{verbatim}
\drawline\photon[\NW\FLIPPED](1500,-18000)[6]
\end{verbatim}
which would draw a photon (or W,Z) starting from the point (1500,-18000),
with distances in centipoints (section 1.5), in the NorthWesterly direction
(\ie towards the upper lefthand corner), in a {\it flipped} configuration
(described below) for an extent of 6 `units'. In the case of photons
each unit is a `half-wiggle'. The actual distance traversed on the page
is not specified since photons come in distinct `quanta', in this case
half-wiggles.
When the above statement is issued a number of parameters are returned.
These may be used by the artiste (this is `Feyn Art').
These are:
\begin{verbatim}
\photonfrontx,\photonfronty: The (x,y) co-ordinates of the front of the line.
\photonbackx,\photonbacky: The (x,y) co-ordinates of the back of the line.
\photonlengthx,\photonlengthy: The (x,y) extent of the line.
\photoncount The number of photons 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}
All of the terms beginning with `\bs particle' may be abbreviated to
`\bs p' plus the rest of the name. For instance, \bs pmidx is the
same as \bs particlemidx \etc
You may be wondering why there is some duplication, such as
\bs pfrontx and \bs photonfrontx. The reason is that terms beginning with
{\it \bs particle} refer to the last particle line drawn by \ddrawline\
whereas those commencing with {\it \bs photon} refer only to the last
{\em photon line} drawn. This distinction often proves to be most
convenient.
To illustrate this point consider the following combination of
statements:
\begin{verbatim}
\input FEYNMAN
\vskip -0.7in
\begin{picture}(18000,8000)
\drawline\gluon[\S\CURLY](0,0)[8]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2500]
\drawline\fermion[\SE\REG](\particlebackx,\particlebacky)[2500]
\drawline\gluon[\S\CURLY](10000,0)[8]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2500]
\drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2500]
\end{picture}
\vskip 1.5in
\end{verbatim}
which produces the following results:
%\input FEYNMAN % MOVED TO FEYNMANDOC.TEX calling routine.
\vskip -0.7in
\begin{picture}(18000,8000)
\drawline\gluon[\S\CURLY](0,0)[8]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2500]
\drawline\fermion[\SE\REG](\particlebackx,\particlebacky)[2500]
\drawline\gluon[\S\CURLY](10000,0)[8]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2500]
\drawline\fermion[\SE\REG](\gluonbackx,\gluonbacky)[2500]
\end{picture}
\vskip 1.5in
We see immediately what the difference is.
In the first diagram \bs particlebackx,y refers, first to the gluon after
it is drawn, and then to the \bs SW fermion after that has been drawn.
If a third reference to those co-ordinates had been made it would have referred
to the final co-ordinates of the \bs SE fermion.
The second gluon line begins 10000 centipoints to the right of the first.
This time the \bs SE fermion commences at \bs gluonbackx,y which is the
end co-ordinates of the gluon and will remain so until the end of the
picture of until another gluon is drawn.
We now proceed to detail the various parameters of the \ddrawline\ command
given above.
\section{The Types of Particle Lines}
The four basic kinds of particle lines which \FEYNMAN\ can draw are
given by the following input parameters:
\begin{verbatim}
\fermion
\scalar
\photon
\gluon
\end{verbatim}
A fifth category, {\tt \bs especial}, which allows the user to define his
own non-standard style of line, has not yet been implemented.
As we have seen this is the first input parameter of \ddrawline\ and
is implemented as
\begin{verbatim}
\drawline\fermion...
\drawline\scalar...
\drawline\photon...
\drawline\gluon...
\end{verbatim}
Note that this is the only argument of \ddrawline\ which is in lowercase
letters. The specifics of each of these will be given in separate sections.
\section{Particle Direction}
Each particle line may be drawn in any of eight possible directions,
specified by the points of the compass with North always understood
as being at the top of the page:
\begin{verbatim}
\N \NE \E \SE \S \SW \W \NW
\end{verbatim}
This is the second argument of \ddrawline.
\begin{verbatim}
\drawline\photon[\NW...
\end{verbatim}
and so forth. The line is drawn from the specified {\it front} point
in the indicated direction. Note that all directions are in uppercase
and don't forget the backslash!
\section{Line Configuration}
Many different particle types are available in a variety of forms.
For the specific forms available see the section on the appropriate
particle type below. The current configurations available are:
\begin{verbatim}
\REG
\FLIPPED
\CURLY
\FLIPPEDCURLY
\FLAT
\FLIPPEDFLAT
\CENTRAL
\FLIPPEDCENTRAL
\LONGPHOTON
\FLIPPEDLONG
\SQUASHEDGLUON
\end{verbatim}
The shape of the individual particle types will be presented shortly but
a few general words might be given here. First, not every particle type
exists in all configurations in all directions. \bs REG is something
of a default (although \verb@\REG@\ must still be included as a parameter
in \ddrawline) and is defined for all particles in all directions.
It may not be your own \ae sthetic favourite, however. \bs FLIPPED lines
are inverted about their axes with respect to the \bs REG lines, but
are otherwise the same. Obviously, since fermions and scalars are merely
straight lines, the \bs REG and \bs FLIPPED configurations will be the same.
In fact for these two particle types \bs REG is the {\bf only}
legitimate configuration (but see \bs THICKLINES at the conclusion of
this section). The other configurations do not, in general, exist for
all of the directions available to a particle. \bs FLIPPEDCURLY,
\bs FLIPPEDCENTRAL, \bs FLIPPEDLONG
and \bs FLIPPEDFLAT are flipped along the direction
axis when compared with \bs CURLY, \bs CENTRAL, \bs LONGPHOTON and \bs FLAT
respectively. \bs CENTRAL and \bs FLIPPEDCENTRAL exist only for
gluons (\bs gluon), \bs LONGPHOTON and \bs FLIPPEDLONG exist only for photons,
while \bs SQUASHED exists only for gluons in the \bs E
direction!
The line configuration is the third input to \ddrawline\ and follows
the direction within the square brackets with no intervening spaces:
\begin{verbatim}
\drawline\scalar[\S\REG]...
\drawline\gluon[\NW\FLIPPED]...
\end{verbatim}
and so forth.
A final word concerns the \bs THINLINES and \bs THICKLINES commands.
When issued prior to a \ddrawline\ or \ddrawvertex\ statement
they cause the particle lines to be drawn in a thin or thick fashion
This remains in effect until superseded or the end of the picture is
encountered. The default is \bs THINLINES.
% The only lines which
%cannot be drawn in a thick mode are photons in the
These commands are identical to the \LaTeX\ \bs thinlines and
\bs thicklines commands except when drawing photons in the
\verb@\E@ and \verb@\W@ directions (any configuration).
These will not be emboldened by \bs thicklines but will be by
\bs THICKLINES. Photons in the
\verb@\N@ and \verb@\S@ directions (any configuration)
are unaffected since they are drawn in an intermediate state.
The following illustrates the difference:
\begin{verbatim}
\begin{picture}(8000,2000)
\drawline\gluon[\E\FLIPPEDCENTRAL](0,0)[5]
\end{picture}
\begin{picture}(8000,2000)
\THICKLINES
\drawline\gluon[\E\FLIPPEDCENTRAL](0,0)[5]
\end{picture}
\end{verbatim}
which produces
\begin{picture}(8000,2000)
\drawline\gluon[\E\FLIPPEDCENTRAL](0,0)[5]
\end{picture}
\begin{picture}(8000,2000)
\thicklines
\drawline\gluon[\E\FLIPPEDCENTRAL](0,0)[5]
\end{picture}
\section{Line Co-ordinate Parameters}
\subsection{Input Parameters}
The fourth and fifth arguments of the \ddrawline\ command
are the (x,y) co-ordinates of the {\em beginning} of the particle
line. these are as measured in {\em centipoints} on the grid
which \FEYNMAN\ has established. They are entered in the format
$(x\ co$-$ordinate,y\ co$-$ordinate)$\ where $x$ and $y$ may be integer
numbers (between, roughly, -30,000 and +30,000) or variables
(counters) with numerical values. A number of variables have been
pre-defined and available for use. The user may also define his own
(see section 4.2.1 on storing information). Some samples may be
illustrative:
\begin{verbatim}
\drawline\fermion[\SE\REG](-1500,12000)[2000]
\drawline\gluon[\E\SQUASHEDGLUON](\photonbackx,\photonbacky)[2]
\drawline\scalar[\N\REG](\Xone,\Yone)[11]
\drawline\photon[\S\FLIPPEDFLAT](3000,\pmidy)[7]
\end{verbatim}
In the above \bs photonbackx and \bs photonbacky are co-ordinates,
presumably returned from a previously drawing a photon.
\bs Xone and \bs Yone are some values stored by the user and
\bs pmidy is the ordinate of the midpoint of the previously drawn line.
Note in the last example how the x co-ordinate is a number while
the y co-ordinate is a variable.
\subsection{Output Parameters}
As discussed in section 2.1 a number of useful positional parameters
are returned when \ddrawline\ is called.
For the appropriate lines the following are defined, each definition superseding
the previous value of the variable.
For all lines:
\begin{verbatim}
\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.
\end{verbatim}
For photons:
\begin{verbatim}
\photonfrontx,\photonfronty: The (x,y) co-ordinates of the front of the photon.
\photonbackx,\photonbacky: The (x,y) co-ordinates of the back of the photon.
\end{verbatim}
For gluons:
\begin{verbatim}
\gluonfrontx,\gluonfronty: The (x,y) co-ordinates of the front of the gluon.
\gluonbackx,\gluonbacky: The (x,y) co-ordinates of the back of the gluon.
\end{verbatim}
For fermions:
\begin{verbatim}
\fermionfrontx,\fermionfronty: The (x,y) co-ordinates of the front of the fermion.
\fermionbackx,\fermionbacky: The (x,y) co-ordinates of the back of the fermion.
\end{verbatim}
For scalars:
\begin{verbatim}
\scalarfrontx,\scalarfronty: The (x,y) co-ordinates of the front of the scalar.
\scalarbackx,\scalarbacky: The (x,y) co-ordinates of the back of the scalar.
\end{verbatim}
As an illustration the command\\
\verb@ \drawline\fermion[\E\REG](0,0)[2000] @ \\
has \\
\begin{verbatim}
\pfrontx=0 \pfronty=0
\pmidx=1000 \pmidy=0
\pbackx=2000 \pbacky=0
\end{verbatim}
\section{Line Length}
\subsection{Input Parameters}
The final parameter to be given to \ddrawline\ is the {\it length}
of the particle to be drawn. The units in which the length is given
vary between the four particle types. For fermions it is simply the
actual length in centipoints. For scalars it is the number of line segments,
each of which is separated by a {\it gap}. The scalar line always begins and
ends on a line segment, never a gap. The default lengths of both segments
and gaps may be overruled by the user (see the section on scalars).
For gluons the length parameter is the {\em number of loops}.
The actual length of each loop depends upon which style is selected and
whether the gluon is drawn diagonally (at a slant) or not.
For photons the unit of measure is not a `wiggle', but a `half-wiggle'.
This enables one to produce a photon which both begins and ends on
the `upward' (or `downward') part of its oscillation. This is illustrated
in the following program:
\begin{verbatim}
\begin{document}
\input FEYNMAN
\textheight 600pt \textwidth 400pt
\begin{picture}(20000,10000)
\drawline\fermion[\E\REG](0,10000)[5000]
\drawline\gluon[\E\REG](10000,10000)[5]
\drawline\photon[\E\REG](0,5000)[5]
\drawline\photon[\E\REG](0,0)[6]
\drawline\scalar[\E\REG](10000,5000)[5]
\seglength=1200 \gaplength=300 % Changes the \scalar defaults.
\drawline\scalar[\E\REG](10000,0)[5]
\end{picture}
\end{document}
\end{verbatim}
\newpage
which produces:
\vskip 0.5in
\begin{picture}(20000,10000)
\drawline\fermion[\E\REG](0,10000)[5000]
\drawline\gluon[\E\REG](10000,10000)[5]
\drawline\photon[\E\REG](0,5000)[5]
\drawline\photon[\E\REG](0,0)[6]
\drawline\scalar[\E\REG](10000,5000)[5]
\seglength=1200 \gaplength=300 % Changes the \scalar defaults.
\drawline\scalar[\E\REG](10000,0)[5]
\end{picture}
\vskip 0.5in
\subsection{Output Parameters}
In the same way as co-ordinates related to the particle are returned,
the {\em displacements} of the line are also given. These are
essentially the $(\Delta x,\Delta y)$\
between the ending and beginning co-ordinates. Thus a particle
drawn in the \bs N direction will have positive \bs particlelengthy
(\bs plengthy for short) and zero \bs particlelengthx.
A particle in the \bs SE direction will have a positive \bs particlelengthx
but a negative \bs particlelengthy (and these will be of the same magnitude).
The full list is:
\begin{verbatim}
\particlelengthx,\particlelengthy: The (x,y) extent of the line.
\photonlengthx,\photonlengthy: The (x,y) extent of the photon.
\gluonlengthx,\gluonlengthy: The (x,y) extent of the gluon.
\scalarlengthx,\scalarlengthy: The (x,y) extent of the scalar.
\fermionlengthx,\fermionlengthy: The (x,y) extent of the fermion.
\fermionlength The total length of the fermion.
\end{verbatim}
A common usage of this parameter would be to draw a fermion line
to be the same length as, say, a gluon line.
\begin{verbatim}
\begin{picture}(9000,4500)
\drawline\gluon[\E\REG](0,4000)[7]
\drawline\fermion[\E\REG](0,0)[\gluonlengthx]
\end{picture}
\end{verbatim}
\vskip 0.5in
\begin{picture}(9000,4500)
\drawline\gluon[\E\REG](0,4000)[7]
\drawline\fermion[\E\REG](0,0)[\gluonlengthx]
\end{picture}
\vskip 0.2in
Each time that a new line is drawn \bs plengthx,y are re-assigned.
\bs photonlengthx,y is only re-assigned when the next photon is drawn,
\bs gluonlengthx,y is only re-assigned when the next gluon is drawn \etc
\newpage
\section{Fermions}
The format for drawing a fermion with \ddrawline\ is:
\begin{verbatim}
\drawline\fermion[<fermion direction>\REG]
<(x,y), the co-ordinates of the beginning of the fermion>[<length(cpt)>]
\end{verbatim}
where the arguments have been described in the preceding sections.
When \FEYNMAN draws a fermion it uses the \bs line facility of \LaTeX.
This places a restriction upon diagonally drawn fermions (those in the
\bs NE, \bs SE, \bs NW and \bs SW directions). The minimum length of such
lines is 1416 centipoints. The user can draw fermions in other directions
(NNE \etc) by utilizing the \bs put command of \LaTeX. The minimum extension
of these lines is at least as great. Fermions drawn in the N,S,E and W
directions have no such restrictions. If attempts are made to draw a fermion
of sub-minimal length it will be as though it were invisible. That is all of
the spacing and parameters will be as before but a blank space will appear
on the page. This effect may be deliberately achieved for {\em any}
particle or vertex using the {\em phantom} facility discussed under
advanced features.
The only option really available for fermions is the use of \bs thicklines
and \bs thinlines as described at the conclusion of section 2.4.
The parameters returned by \ddrawline\ when a fermion is drawn are:
\begin{verbatim}
\fermionfrontx,\fermionfronty: The (x,y) co-ordinates of the front of the line.
\fermionbackx,\fermionbacky: The (x,y) co-ordinates of the back of the line.
\fermionlengthx,\fermionlengthy: The (x,y) extent of the line.
\fermionlength The total length of the line.
\fermioncount The number of fermions 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}
As an example:
\begin{verbatim}
\begin{picture}(8000,8000)
\drawline\fermion[\E\REG](0,0)[6000]
\THICKLINES
\drawline\fermion[\N\REG](\fermionbackx,\pbacky)[5000]
\drawline\fermion[\SW\REG](\fermionbackx,\fermionbacky)[4000]
\THINLINES
\drawline\fermion[\NW\REG](\pmidx,\pmidy)[2000]
\drawline\fermion[\W\REG](\pfrontx,\pfronty)[\fermionlengthy]
\end{picture}
\end{verbatim}
which produces:
\vskip -0.25in \hskip 1.75in
\begin{picture}(8000,8000)
\drawline\fermion[\E\REG](0,0)[6000]
\thicklines
\drawline\fermion[\N\REG](\fermionbackx,\pbacky)[5000]
\drawline\fermion[\SW\REG](\fermionbackx,\fermionbacky)[4000]
\thinlines
\drawline\fermion[\NW\REG](\pmidx,\pmidy)[2000]
\drawline\fermion[\W\REG](\pfrontx,\pfronty)[\fermionlengthy]
\end{picture}
%\bigskip
\newpage
\section{Scalars}
\subsection{The Anatomy of a Scalar}
A scalar particle (eg. a Higgs) is generally drawn as a dashed line,
that is a series of line {\it segments} separated by {\it gaps}.
The format for drawing a scalar with \ddrawline\ is:
\begin{verbatim}
\drawline\scalar[<scalar direction>\REG]
<(x,y), the co-ordinates of the beginning of the scalar>
[<number of segments>]
\end{verbatim}
We note the similarity between the fermion and scalar lines.
The principal difference is in the units of length. Here the extent of
the line is given by an integral number of segments. These will be
of equal length and equally spaced. The same limitations on the
length of fermion lines applies here: diagonal (NW, NE \etc)
line segments may not be shorter than 1416 centipoints, which is
the default length for all directions. The default gap length is
850 centipoints and there is no innate limitation on this value
(other than it must not be negative or larger than the page size).
Attempts to draw a slanted scalar with segments of under 1416 centipoints
will lead to a blank space in the diagram.
The parameters returned by \ddrawline\ when a scalar is drawn are:
\begin{verbatim}
\scalarfrontx,\scalarfronty: The (x,y) co-ordinates of the front of the scalar.
\scalarbackx,\scalarbacky: The (x,y) co-ordinates of the back of the scalar.
\scalarlengthx,\scalarlengthy: The (x,y) extent of the scalar.
\scalarcount: The total number of scalars 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}
\subsection{Adjusting the Spacing}
The segment length is given, in centipoints, by the variable
\bs seglength and the gap length by \bs gaplength. Both are
adjustable by the user by issuing the commands:
\begin{verbatim}
\global\seglength=<your length in centipoints>
\global\gaplength=<your length in centipoints>
\end{verbatim}
just prior to a \ddrawline\bs scalar command. After this they automatically
return to their default values of 1416 and 850. If only one is adjusted the
other will retain its default value. The modifiers \bs thicklines and
\bs thinlines work normally here with \bs thinlines the default (but
\bs thicklines will remain in effect until \bs thinlines or \eendpic\
is encountered).
\bigskip
These features are illustrated by the following sample file:
\newpage
\begin{verbatim}
\begin{picture}(25000,25000)
% First picture:
\drawline\scalar[\E\REG](6000,0)[5]
\drawline\fermion[\SE\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\NE\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\SW\REG](\scalarfrontx,\scalarfronty)[2000]
\drawline\fermion[\NW\REG](\scalarfrontx,\scalarfronty)[2000]
\global\seglength=1000 \global\gaplength=250
\drawline\scalar[\W\REG](\pbackx,\pbacky)[5]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2000]
\drawline\fermion[\NW\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\NE\REG](\scalarfrontx,\scalarfronty)[2000]
\put(4000,0){1}
% Second Picture:
\THICKLINES
\drawline\fermion[\N\REG](23000,3000)[12345]
\global\gaplength=473
\drawline\scalar[\NW\REG](\pbackx,\fermionbacky)[3]
\global\gaplength=473
\drawline\scalar[\NE\REG](\fermionbackx,\pfronty)[3]
\drawline\scalar[\SW\REG](\fermionfrontx,\fermionfronty)[3]
\drawline\scalar[\SE\REG](\fermionfrontx,\fermionfronty)[3]
\put(23500,14000){2}
% Third Picture:
\THINLINES
\global\gaplength=0 \global\seglength=1000
\drawline\scalar[\S\REG](1000,16000)[4]
\drawline\fermion[\NW\REG](1000,16000)[1500]
\drawline\fermion[\NE\REG](1000,16000)[1500]
\drawline\fermion[\SW\REG](1000,12000)[1500]
\drawline\fermion[\SE\REG](1000,12000)[1500]
\put(1500,14000){3}
% Fourth Picture:
\global\gaplength=500 \global\seglength=500
\thicklines
\drawline\scalar[\NE\REG](6000,7000)[10]
\put(\pmidx,\pmidy){4}
\drawline\fermion[\W\REG](\scalarfrontx,\scalarfronty)[2500]
\drawline\fermion[\S\REG](\scalarfrontx,\scalarfronty)[2500]
\drawline\fermion[\E\REG](\scalarbackx,\scalarbacky)[2500]
\drawline\fermion[\N\REG](\scalarbackx,\scalarbacky)[2500]
\end{picture}
\end{verbatim}
which produces:
\begin{picture}(25000,25000)
% First picture:
\drawline\scalar[\E\REG](6000,0)[5]
\drawline\fermion[\SE\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\NE\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\SW\REG](\scalarfrontx,\scalarfronty)[2000]
\drawline\fermion[\NW\REG](\scalarfrontx,\scalarfronty)[2000]
\global\seglength=1000 \global\gaplength=250
\drawline\scalar[\W\REG](\pbackx,\pbacky)[5]
\drawline\fermion[\SW\REG](\particlebackx,\particlebacky)[2000]
\drawline\fermion[\NW\REG](\scalarbackx,\scalarbacky)[2000]
\drawline\fermion[\NE\REG](\scalarfrontx,\scalarfronty)[2000]
\put(4000,0){1}
% Second Picture:
\thicklines
\drawline\fermion[\N\REG](23000,3000)[12345]
\global\gaplength=473
\drawline\scalar[\NW\REG](\pbackx,\fermionbacky)[3]
\global\gaplength=473
\drawline\scalar[\NE\REG](\fermionbackx,\pfronty)[3]
\drawline\scalar[\SW\REG](\fermionfrontx,\fermionfronty)[3]
\drawline\scalar[\SE\REG](\fermionfrontx,\fermionfronty)[3]
\put(23500,14000){2}
% Third Picture:
\thinlines
\global\gaplength=0 \global\seglength=1000
\drawline\scalar[\S\REG](1000,16000)[4]
\drawline\fermion[\NW\REG](1000,16000)[1500]
\drawline\fermion[\NE\REG](1000,16000)[1500]
\drawline\fermion[\SW\REG](1000,12000)[1500]
\drawline\fermion[\SE\REG](1000,12000)[1500]
\put(1500,14000){3}
% Fourth Picture:
\global\gaplength=500 \global\seglength=500
\thicklines
\drawline\scalar[\NE\REG](6000,7000)[10]
\put(\pmidx,\pmidy){4}
\drawline\fermion[\W\REG](\scalarfrontx,\scalarfronty)[2500]
\drawline\fermion[\S\REG](\scalarfrontx,\scalarfronty)[2500]
\drawline\fermion[\E\REG](\scalarbackx,\scalarbacky)[2500]
\drawline\fermion[\N\REG](\scalarbackx,\scalarbacky)[2500]
\end{picture}
\bigskip
\bigskip
\bigskip
There are a few points of note. In the first picture observe how
\bs pbackx,y ($\equiv$\bs particlebackx,y) is used as opposed to
\bs scalarbackx,y. For more on this point see section 2.1.
Also note that the \bs seglength assignments stay in effect until
the next scalar is drawn. The second figure illustrates how
\bs gaplength automatically reverts to its default and further
demonstrates the assignments of the co-ordinate variables.
The third diagram shows that a zero gaplength creates a fermion
and that numerical co-ordinates may be used just as easily as
the pre-assigned positioning variables. This is also illustrated by
the positioning of the numerical labels (1,2,3,4) which was accomplished
with minimal thought. Finally the fourth diagram shows what happens when the
value of \bs seglength is reduced to less that 1416 for a diagonal
(non-horizontal, non-vertical) scalar. It also demonstrates how to
locate the central point of a line.
\section{Photons}
\subsection{The Anatomy of a Photon}
A photon line consists of a series of `wiggles' or undulations.
The length of each undulation depends upon the style of photon selected.
The format for drawing a photon with \ddrawline\ is:
\begin{verbatim}
\drawline\photon[<photon direction><photon style>]
<(x,y), the co-ordinates of the beginning of the photon>
[<number of HALF-wiggles>]
\end{verbatim}
The reason for specifying the number of {\it half}-wiggles is that it
is sometimes convenient to have a line begin and end in either orientation
(see section 2.6.1 for an example of this).
The styles currently available for photons are:
|