source: HiSusy/trunk/Pythia8/pythia8170/phpdoc/ParticleProperties.php @ 1

Last change on this file since 1 was 1, checked in by zerwas, 11 years ago

first import of structure, PYTHIA8 and DELPHES
File size: 31.2 KB
Line 
1<html>
2<head>
3<title>Particle Properties</title>
4<link rel="stylesheet" type="text/css" href="pythia.css"/>
5<link rel="shortcut icon" href="pythia32.gif"/>
6</head>
7<body>
8
9<script language=javascript type=text/javascript>
10function stopRKey(evt) {
11var evt = (evt) ? evt : ((event) ? event : null);
12var node = (evt.target) ? evt.target :((evt.srcElement) ? evt.srcElement : null);
13if ((evt.keyCode == 13) && (node.type=="text"))
14{return false;}
15}
16
17document.onkeypress = stopRKey;
18</script>
19<?php
20if($_POST['saved'] == 1) {
21if($_POST['filepath'] != "files/") {
22echo "<font color='red'>SETTINGS SAVED TO FILE</font><br/><br/>"; }
23else {
24echo "<font color='red'>NO FILE SELECTED YET.. PLEASE DO SO </font><a href='SaveSettings.php'>HERE</a><br/><br/>"; }
25}
26?>
27
28<form method='post' action='ParticleProperties.php'>
29
30<h2>Particle Properties</h2>
31
32A <code>Particle</code> corresponds to one entry/slot in the
33event record. Its properties therefore is a mix of ones belonging
34to a particle-as-such, like its identity code or four-momentum,
35and ones related to the event-as-a-whole, like which mother it has.
36
37<p/>
38What is stored for each particle is
39<ul>
40<li>the identity code,</li> 
41<li>the status code,</li> 
42<li>two mother indices,</li>
43<li>two daughter indices,</li> 
44<li>a colour and an anticolour index,</li> 
45<li>the four-momentum and mass,</li>
46<li>the scale at which the particle was produced (optional),</li> 
47<li>the polarization/spin/helicity of the particle (optional),</li>
48<li>the production vertex and proper lifetime (optional),</li>
49<li>a pointer to the particle kind in the particle data table, and</li>
50<li>a pointer to the whole particle data table.</li>
51</ul>
52From these, a number of further quantities may be derived.
53
54<h3>Basic output methods</h3>
55
56The following member functions can be used to extract the most important
57information:
58
59<a name="method1"></a>
60<p/><strong>int Particle::id() &nbsp;</strong> <br/>
61the identity of a particle, according to the PDG particle codes
62[<a href="Bibliography.php" target="page">Yao06</a>].
63 
64
65<a name="method2"></a>
66<p/><strong>int Particle::status() &nbsp;</strong> <br/>
67status code. The status code includes information on how a particle was
68produced, i.e. where in the program execution it was inserted into the
69event record, and why. It also tells whether the particle is still present
70or not. It does not tell how a particle disappeared, whether by a decay,
71a shower branching, a hadronization process, or whatever, but this is
72implicit in the status code of its daughter(s). The basic scheme is:
73<ul>
74<li>status = +- (10 * i + j)</li>
75<li> +          : still remaining particles</li>
76<li> -          : decayed/branched/fragmented/... and not remaining</li>
77<li> i =  1 - 9 : stage of event generation inside PYTHIA</li>
78<li> i = 10 -19 : reserved for future expansion</li>
79<li> i >= 20    : free for add-on programs</li>
80<li> j = 1 - 9  : further specification</li>
81</ul>
82In detail, the list of used or foreseen status codes is:
83<ul>
84<li>11 - 19 : beam particles</li> 
85  <ul>
86  <li>11 : the event as a whole</li>
87  <li>12 : incoming beam</li>
88  <li>13 : incoming beam-inside-beam (e.g. <i>gamma</i>
89           inside <i>e</i>)</li>
90  <li>14 : outgoing elastically scattered</li>
91  <li>15 : outgoing diffractively scattered</li>
92  </ul>
93<li>21 - 29 : particles of the hardest subprocess</li>
94  <ul>
95  <li>21 : incoming</li>
96  <li>22 : intermediate (intended to have preserved mass)</li>
97  <li>23 : outgoing</li>
98  </ul>
99<li>31 - 39 : particles of subsequent subprocesses</li>
100  <ul>
101  <li>31 : incoming</li>
102  <li>32 : intermediate (intended to have preserved mass)</li>
103  <li>33 : outgoing</li>
104  <li>34 : incoming that has already scattered</li>
105  </ul>
106<li>41 - 49 : particles produced by initial-state-showers</li>
107  <ul>
108  <li>41 : incoming on spacelike main branch</li>
109  <li>42 : incoming copy of recoiler</li>
110  <li>43 : outgoing produced by a branching</li>
111  <li>44 : outgoing shifted by a branching</li>
112  <li>45 : incoming rescattered parton, with changed kinematics
113           owing to ISR in the mother system (cf. status 34)</li>
114  <li>46 : incoming copy of recoiler when this is a rescattered
115           parton (cf. status 42)</li>
116  </ul>
117<li>51 - 59 : particles produced by final-state-showers</li>
118  <ul>
119  <li>51 : outgoing produced by parton branching</li>
120  <li>52 : outgoing copy of recoiler, with changed momentum</li> 
121  <li>53 : copy of recoiler when this is incoming parton,
122           with changed momentum</li> 
123  <li>54 : copy of a recoiler, when in the initial state of a
124           different system from the radiator</li>
125  <li>55 : copy of a recoiler, when in the final state of a
126           different system from the radiator</li>
127  </ul>
128<li>61 - 69 : particles produced by beam-remnant treatment</li>
129  <ul>
130  <li>61 : incoming subprocess particle with primordial <i>kT</i>
131           included</li>
132  <li>62 : outgoing subprocess particle with primordial <i>kT</i>
133           included</li>
134  <li>63 : outgoing beam remnant</li> 
135  </ul>
136<li>71 - 79 : partons in preparation of hadronization process</li>
137  <ul>
138  <li>71 : copied partons to collect into contiguous colour singlet</li> 
139  <li>72 : copied recoiling singlet when ministring collapses to
140           one hadron and momentum has to be reshuffled</li>
141  <li>73 : combination of very nearby partons into one</li>
142  <li>74 : combination of two junction quarks (+ nearby gluons)
143           to a diquark</li> 
144  <li>75 : gluons split to decouple a junction-antijunction pair</li>
145  <li>76 : partons with momentum shuffled to decouple a
146           junction-antijunction pair </li>
147  <li>77 : temporary opposing parton when fragmenting first two
148           strings in to junction (should disappear again)</li>
149  <li>78 : temporary combined diquark end when fragmenting last
150           string in to junction (should disappear again)</li>
151  </ul>
152<li>81 - 89 : primary hadrons produced by hadronization process</li>
153  <ul>
154  <li>81 : from ministring into one hadron</li>
155  <li>82 : from ministring into two hadrons</li>
156  <li>83, 84 : from normal string (the difference between the two
157           is technical, whether fragmented off from the top of the
158           string system or from the bottom, useful for debug only)</li>
159  <li>85, 86 : primary produced hadrons in junction frogmentation of
160           the first two string legs in to the junction,
161           in order of treatment</li>
162  </ul>
163<li>91 - 99 : particles produced in decay process, or by Bose-Einstein
164  effects</li>
165  <ul>
166  <li>91 : normal decay products</li>
167  <li>92 : decay products after oscillation <i>B0 &lt;-> B0bar</i> or
168           <i>B_s0 &lt;-> B_s0bar</i></li>
169  <li>93, 94 : decay handled by external program, normally
170           or with oscillation</li>
171  <li>99 : particles with momenta shifted by Bose-Einstein effects
172           (not a proper decay, but bookkept as an <i>1 -> 1</i> such,
173           happening after decays of short-lived resonances but before
174           decays of longer-lived particles)</li>
175  </ul>
176<li>101 - 109 : particles in the handling of R-hadron production and
177  decay, i.e. long-lived (or stable) particles containing a very heavy
178  flavour</li>
179  <ul>
180  <li>101 : when a string system contains two such long-lived particles,
181            the system is split up by the production of a new q-qbar
182            pair (bookkept as decay chains that seemingly need not conserve
183            flavour etc., but do when considered together)</li>
184  <li>102 : partons rearranged from the long-lived particle end to prepare
185            for fragmentation from this end</li>
186  <li>103 : intermediate "half-R-hadron" formed when a colour octet particle
187            (like the gluino) has been fragmented on one side, but not yet on
188            the other</li>
189  <li>104 : an R-hadron</li>
190  <li>105 : partons or particles formed together with the R-hadron during
191            the fragmentation treatment</li>
192  <li>106 : subdivision of an R-hadron into its flavour content, with
193           momentum split accordingly, in preparation of the decay of
194           the heavy new particle, if it is unstable</li>
195  <li>107 : two temporary leftover gluons joined into one in the formation
196          of a gluino-gluon R-hadron.</li>
197  </ul>
198<li>111 - 199 : reserved for future expansion</li>
199<li>201 - : free to be used by anybody</li>  
200</ul>
201 
202
203<a name="method3"></a>
204<p/><strong>int Particle::mother1() &nbsp;</strong> <br/>
205 
206<strong>int Particle::mother2() &nbsp;</strong> <br/>
207the indices in the event record where the first and last mothers are
208stored, if any. There are five allowed combinations of <code>mother1</code>
209and <code>mother2</code>:
210<ol>
211<li><code>mother1 = mother2 = 0</code>: for lines 0 - 2, where line 0
212represents the event as a whole, and 1 and 2 the two incoming
213beam particles; </li>
214<li><code>mother1 = mother2 > 0</code>: the particle is a "carbon copy"
215of its mother, but with changed momentum as a "recoil"  effect,
216e.g. in a shower;</li>
217<li><code>mother1 > 0, mother2 = 0</code>: the "normal" mother case, where
218it is meaningful to speak of one single mother to several products,
219in a shower or decay;</li>
220<li><code>mother1 &lt; mother2</code>, both > 0, for
221<code>abs(status) = 81 - 86</code>: primary hadrons produced from the
222fragmentation of a string spanning the range from <code>mother1</code>
223to <code>mother2</code>, so that all partons in this range should be
224considered mothers; and analogously for
225<code>abs(status) = 101 - 106</code>, the formation of R-hadrons;</li>
226<li><code>mother1 &lt; mother2</code>, both > 0, except case 4: particles
227with two truly different mothers, in particular the particles emerging
228from a hard <i>2 -> n</i> interaction.</li>
229</ol>   
230<br/><b>Note 1:</b> in backwards evolution of initial-state showers,
231the mother may well appear below the daughter in the event record.
232<br/><b>Note 2:</b> the <code>motherList(i)</code> method of the
233<code>Event</code> class returns a vector of all the mothers,
234providing a uniform representation for all five cases.
235 
236
237<a name="method4"></a>
238<p/><strong>int Particle::daughter1() &nbsp;</strong> <br/>
239 
240<strong>int Particle::daughter2() &nbsp;</strong> <br/>
241the indices in the event record where the first and last daughters
242are stored, if any. There are five allowed combinations of
243<code>daughter1</code> and <code>daughter2</code>:
244<ol>
245<li><code>daughter1 = daughter2 = 0</code>: there are no daughters
246(so far);</li>
247<li><code>daughter1 = daughter2 > 0</code>: the particle has a
248"carbon copy" as its sole daughter, but with changed momentum
249as a "recoil" effect, e.g. in a shower;</li>
250<li><code>daughter1 > 0, daughter2 = 0</code>: each of the incoming beams
251has only (at most) one daughter, namely the initiator parton of the
252hardest interaction; further, in a <i>2 -> 1</i> hard interaction,
253like <i>q qbar -> Z^0</i>, or in a clustering of two nearby partons,
254the initial partons only have this one daughter;</li>
255<li><code>daughter1 &lt; daughter2</code>, both > 0: the particle has
256a range of decay products from <code>daughter1</code> to
257<code>daughter2</code>;</li> <li><code>daughter2 &lt; daughter1</code>,
258both > 0: the particle has two separately stored decay products (e.g.
259in backwards evolution of initial-state showers).</li>
260</ol>
261<br/><b>Note 1:</b> in backwards evolution of initial-state showers, the
262daughters may well appear below the mother in the event record.
263<br/><b>Note 2:</b> the mother-daughter relation normally is reciprocal,
264but not always. An example is hadron beams (indices 1 and 2), where each
265beam remnant and the initiator of each multiparton interaction has the
266respective beam as mother, but the beam itself only has the initiator
267of the hardest interaction as daughter.
268<br/><b>Note 3:</b> the <code>daughterList(i)</code> method of the
269<code>Event</code> class returns a vector of all the daughters,
270providing a uniform representation for all five cases. With this method,
271also all the daughters of the beams are caught, with the initiators of
272the basic process given first,  while the rest are in no guaranteed order
273(since they are found by a scanning of the event record for particles
274with the beam as mother, with no further information).
275 
276
277<a name="method5"></a>
278<p/><strong>int Particle::col() &nbsp;</strong> <br/>
279 
280<strong>int Particle::acol() &nbsp;</strong> <br/>
281the colour and anticolour tags, Les Houches Accord [<a href="Bibliography.php" target="page">Boo01</a>]
282style (starting from tag 101 by default, see below).
283<br/><b>Note:</b> in the preliminary implementation of colour sextets
284(exotic BSM particles) that exists since PYTHIA 8.150, a negative
285anticolour tag is interpreted as an additional positive colour tag,
286and vice versa. 
287 
288
289<a name="method6"></a>
290<p/><strong>double Particle::px() &nbsp;</strong> <br/>
291 
292<strong>double Particle::py() &nbsp;</strong> <br/>
293 
294<strong>double Particle::pz() &nbsp;</strong> <br/>
295 
296<strong>double Particle::e() &nbsp;</strong> <br/>
297the particle four-momentum components.
298 
299
300<a name="method7"></a>
301<p/><strong>Vec4 Particle::p() &nbsp;</strong> <br/>
302the particle four-momentum vector, with components as above.
303 
304
305<a name="method8"></a>
306<p/><strong>double Particle::m() &nbsp;</strong> <br/>
307the particle mass, stored with a minus sign (times the absolute value)
308for spacelike virtual particles.
309 
310
311<a name="method9"></a>
312<p/><strong>double Particle::scale() &nbsp;</strong> <br/>
313the scale at which a parton was produced, which can be used to restrict
314its radiation to lower scales in subsequent steps of the shower evolution.
315Note that scale is linear in momenta, not quadratic (i.e. <i>Q</i>,
316not <i>Q^2</i>).
317 
318
319<a name="method10"></a>
320<p/><strong>double Particle::pol() &nbsp;</strong> <br/>
321the polarization/spin/helicity of a particle. Currently Pythia does not
322use this variable for any internal operations, so its meaning is not
323uniquely defined. The LHA standard sets <code>SPINUP</code> to be the
324cosine of the angle between the spin vector and the 3-momentum of the
325decaying particle in the lab frame, i.e. restricted to be between +1
326and -1. A more convenient choice could be the same quantity in the rest
327frame of the particle production, either the hard subprocess or the
328mother particle of a decay. Unknown or unpolarized particles should
329be assigned the value 9.
330 
331
332<a name="method11"></a>
333<p/><strong>double Particle::xProd() &nbsp;</strong> <br/>
334 
335<strong>double Particle::yProd() &nbsp;</strong> <br/>
336 
337<strong>double Particle::zProd() &nbsp;</strong> <br/>
338 
339<strong>double Particle::tProd() &nbsp;</strong> <br/>
340the production vertex coordinates, in mm or mm/c.
341 
342
343<a name="method12"></a>
344<p/><strong>Vec4 Particle::vProd() &nbsp;</strong> <br/>
345The production vertex four-vector. Note that the components of a
346<code>Vec4</code> are named <code>px(), py(), pz() and e()</code>
347which of course then should be reinterpreted as above.
348 
349
350<a name="method13"></a>
351<p/><strong>double Particle::tau() &nbsp;</strong> <br/>
352the proper lifetime, in mm/c. It is assigned for all hadrons with
353positive nominal <i>tau</i>, <i>tau_0 > 0</i>, because it can be used
354by PYTHIA to decide whether a particle should or should not be allowed
355to decay, e.g. based on the decay vertex distance to the primary interaction
356vertex.
357 
358
359<h3>Input methods</h3>
360
361The same method names as above are also overloaded in versions that
362set values. These have an input argument of the same type as the
363respective output above, and are of type <code>void</code>.
364
365<p/>
366There are also a few alternative methods for input:
367
368<a name="method14"></a>
369<p/><strong>void Particle::statusPos() &nbsp;</strong> <br/>
370 
371<strong>void Particle::statusNeg() &nbsp;</strong> <br/>
372sets the status sign positive or negative, without changing the absolute value.
373 
374
375<a name="method15"></a>
376<p/><strong>void Particle::statusCode(int code) &nbsp;</strong> <br/>
377changes the absolute value but retains the original sign.
378 
379
380<a name="method16"></a>
381<p/><strong>void Particle::mothers(int mother1, int mother2) &nbsp;</strong> <br/>
382sets both mothers in one go.
383 
384
385<a name="method17"></a>
386<p/><strong>void Particle::daughters(int daughter1, int daughter2) &nbsp;</strong> <br/>
387sets both daughters in one go.
388 
389
390<a name="method18"></a>
391<p/><strong>void Particle::cols(int col, int acol) &nbsp;</strong> <br/>
392sets both colour and anticolour in one go.
393 
394
395<a name="method19"></a>
396<p/><strong>void Particle::p(double px, double py, double pz, double e) &nbsp;</strong> <br/>
397sets the four-momentum components in one go.
398 
399
400<a name="method20"></a>
401<p/><strong>void Particle::vProd(double xProd, double yProd, double zProd, double tProd) &nbsp;</strong> <br/>
402sets the production vertex components in one go.
403 
404
405<h3>Further output methods</h3>
406
407<p/>
408In addition, a number of derived quantities can easily be obtained,
409but cannot be set, such as:
410
411<a name="method21"></a>
412<p/><strong>int Particle::idAbs() &nbsp;</strong> <br/>
413the absolute value of the particle identity code.
414 
415
416<a name="method22"></a>
417<p/><strong>int Particle::statusAbs() &nbsp;</strong> <br/>
418the absolute value of the status code.
419 
420
421<a name="method23"></a>
422<p/><strong>bool Particle::isFinal() &nbsp;</strong> <br/>
423true for a remaining particle, i.e. one with positive status code,
424else false. Thus, after an event has been fully generated, it
425separates the final-state particles from intermediate-stage ones.
426(If used earlier in the generation process, a particle then
427considered final may well decay later.) 
428 
429
430<a name="method24"></a>
431<p/><strong>bool Particle::isRescatteredIncoming() &nbsp;</strong> <br/>
432true for particles with a status code -34, -45, -46 or -54, else false.
433This singles out partons that have been created in a previous
434scattering but here are bookkept as belonging to the incoming state
435of another scattering.
436 
437
438<a name="method25"></a>
439<p/><strong>bool Particle::hasVertex() &nbsp;</strong> <br/>
440production vertex has been set; if false then production at the origin
441is assumed.
442 
443
444<a name="method26"></a>
445<p/><strong>double Particle::m2() &nbsp;</strong> <br/>
446squared mass, which can be negative for spacelike partons.
447 
448
449<a name="method27"></a>
450<p/><strong>double Particle::mCalc() &nbsp;</strong> <br/>
451 
452<strong>double Particle::m2Calc() &nbsp;</strong> <br/>
453(squared) mass calculated from the four-momentum; should agree
454with <code>m(), m2()</code> up to roundoff. Negative for spacelike
455virtualities.
456 
457
458<a name="method28"></a>
459<p/><strong>double Particle::eCalc() &nbsp;</strong> <br/>
460energy calculated from the mass and three-momentum; should agree
461with <code>e()</code> up to roundoff. For spacelike partons a
462positive-energy  solution is picked. This need not be the correct
463one, so it is recommended not to use the method in such cases.
464 
465
466<a name="method29"></a>
467<p/><strong>double Particle::pT() &nbsp;</strong> <br/>
468 
469<strong>double Particle::pT2() &nbsp;</strong> <br/>
470(squared) transverse momentum.
471 
472
473<a name="method30"></a>
474<p/><strong>double Particle::mT() &nbsp;</strong> <br/>
475 
476<strong>double Particle::mT2() &nbsp;</strong> <br/>
477(squared) transverse mass. If <i>m_T^2</i> is negative, which can happen
478for a spacelike parton, then <code>mT()</code> returns
479<i>-sqrt(-m_T^2)</i>, by analogy with the negative sign used to store
480spacelike masses. 
481 
482
483<a name="method31"></a>
484<p/><strong>double Particle::pAbs() &nbsp;</strong> <br/>
485 
486<strong>double Particle::pAbs2() &nbsp;</strong> <br/>
487(squared) three-momentum size.
488 
489
490<a name="method32"></a>
491<p/><strong>double Particle::eT() &nbsp;</strong> <br/>
492 
493<strong>double Particle::eT2() &nbsp;</strong> <br/>
494(squared) transverse energy,
495<i>eT = e * sin(theta) = e * pT / pAbs</i>.
496 
497
498<a name="method33"></a>
499<p/><strong>double Particle::theta() &nbsp;</strong> <br/>
500 
501<strong>double Particle::phi() &nbsp;</strong> <br/>
502polar and azimuthal angle.
503 
504
505<a name="method34"></a>
506<p/><strong>double Particle::thetaXZ() &nbsp;</strong> <br/>
507angle in the <i>(p_x, p_z)</i> plane, between <i>-pi</i> and
508<i>+pi</i>, with 0 along the <i>+z</i> axis
509 
510
511<a name="method35"></a>
512<p/><strong>double Particle::pPos() &nbsp;</strong> <br/>
513 
514<strong>double Particle::pNeg() &nbsp;</strong> <br/>
515<i>E +- p_z</i>.
516 
517
518<a name="method36"></a>
519<p/><strong>double Particle::y() &nbsp;</strong> <br/>
520 
521<strong>double Particle::eta() &nbsp;</strong> <br/>
522rapidity and pseudorapidity.
523 
524
525<a name="method37"></a>
526<p/><strong>double Particle::xDec() &nbsp;</strong> <br/>
527 
528<strong>double Particle::yDec() &nbsp;</strong> <br/>
529 
530<strong>double Particle::zDec() &nbsp;</strong> <br/>
531 
532<strong>double Particle::tDec() &nbsp;</strong> <br/>
533 
534<strong>Vec4 Particle::vDec() &nbsp;</strong> <br/>
535the decay vertex coordinates, in mm or mm/c. This decay vertex is
536calculated from the production vertex, the proper lifetime and the
537four-momentum assuming no magnetic field or other detector interference.
538It can be used to decide whether a decay should be performed or not,
539and thus is defined also for particles which PYTHIA did not let decay.
540 
541
542<p/>
543Each Particle contains a pointer to the respective
544<code>ParticleDataEntry</code> object in the
545<?php $filepath = $_GET["filepath"];
546echo "<a href='ParticleDataScheme.php?filepath=".$filepath."' target='page'>";?>particle data tables</a>.
547This gives access to properties of the particle species as such. It is
548there mainly for convenience, and should be thrown if an event is
549written to disk, to avoid any problems of object persistency. Should
550an event later be read back in, the pointer will be recreated from the
551<code>id</code> code if the normal input methods are used. (Use the
552<code><?php $filepath = $_GET["filepath"];
553echo "<a href='EventRecord.php?filepath=".$filepath."' target='page'>";?>Event::restorePtrs()</a></code> method
554if your persistency scheme bypasses the normal methods.) This pointer is
555used by the following member functions:
556
557<a name="method38"></a>
558<p/><strong>string Particle::name() &nbsp;</strong> <br/>
559the name of the particle.
560 
561
562<a name="method39"></a>
563<p/><strong>string Particle::nameWithStatus() &nbsp;</strong> <br/>
564as above, but for negative-status particles the name is given in
565brackets to emphasize that they are intermediaries.
566 
567
568<a name="method40"></a>
569<p/><strong>int Particle::spinType() &nbsp;</strong> <br/>
570<i>2 *spin + 1</i> when defined, else 0.
571 
572
573<a name="method41"></a>
574<p/><strong>double Particle::charge() &nbsp;</strong> <br/>
575 
576<strong>int Particle::chargeType() &nbsp;</strong> <br/>
577charge, and three times it to make an integer.
578 
579
580<a name="method42"></a>
581<p/><strong>bool Particle::isCharged() &nbsp;</strong> <br/>
582 
583<strong>bool Particle::isNeutral() &nbsp;</strong> <br/>
584charge different from or equal to 0.
585 
586
587<a name="method43"></a>
588<p/><strong>int Particle::colType() &nbsp;</strong> <br/>
5890 for colour singlets, 1 for triplets,
590-1 for antitriplets and 2 for octets. (A preliminary implementation of
591colour sextets also exists, using 3 for sextets and -3 for antisextets.)
592 
593
594<a name="method44"></a>
595<p/><strong>double Particle::m0() &nbsp;</strong> <br/>
596the nominal mass of the particle, according to the data tables.
597 
598
599<a name="method45"></a>
600<p/><strong>double Particle::mWidth() &nbsp;</strong> <br/>
601 
602<strong>double Particle::mMin() &nbsp;</strong> <br/>
603 
604<strong>double Particle::mMax() &nbsp;</strong> <br/>
605the width of the particle, and the minimum and maximum allowed mass value
606for particles with a width, according to the data tables.
607 
608
609<a name="method46"></a>
610<p/><strong>double Particle::mass() &nbsp;</strong> <br/>
611the mass of the particle, picked according to a Breit-Wigner
612distribution for particles with width. It is different each time called,
613and is therefore only used once per particle to set its mass
614<code>m()</code>.
615 
616
617<a name="method47"></a>
618<p/><strong>double Particle::constituentMass() &nbsp;</strong> <br/>
619will give the constituent masses for quarks and diquarks,
620else the same masses as with <code>m0()</code>.
621 
622
623<a name="method48"></a>
624<p/><strong>double Particle::tau0() &nbsp;</strong> <br/>
625the nominal lifetime <i>tau_0 > 0</i>, in mm/c, of the particle species.
626It is used to assign the actual lifetime <i>tau</i>.
627 
628
629<a name="method49"></a>
630<p/><strong>bool Particle::mayDecay() &nbsp;</strong> <br/>
631flag whether particle has been declared unstable or not, offering
632the main user switch to select which particle species to decay.
633 
634
635<a name="method50"></a>
636<p/><strong>bool Particle::canDecay() &nbsp;</strong> <br/>
637flag whether decay modes have been declared for a particle,
638so that it could be decayed, should that be requested.
639 
640
641<a name="method51"></a>
642<p/><strong>bool Particle::doExternalDecay() &nbsp;</strong> <br/>
643particles that are decayed by an external program.
644 
645
646<a name="method52"></a>
647<p/><strong>bool Particle::isResonance() &nbsp;</strong> <br/>
648particles where the decay is to be treated as part of the hard process,
649typically with nominal mass above 20 GeV (<i>W^+-, Z^0, t, ...</i>).
650 
651
652<a name="method53"></a>
653<p/><strong>bool Particle::isVisible() &nbsp;</strong> <br/>
654particles with strong or electric charge, or composed of ones having it, 
655which thereby should be considered visible in a normal detector.
656 
657
658<a name="method54"></a>
659<p/><strong>bool Particle::isLepton() &nbsp;</strong> <br/>
660true for a lepton or an antilepton (including neutrinos).
661 
662
663<a name="method55"></a>
664<p/><strong>bool Particle::isQuark() &nbsp;</strong> <br/>
665true for a quark or an antiquark.
666 
667
668<a name="method56"></a>
669<p/><strong>bool Particle::isGluon() &nbsp;</strong> <br/>
670true for a gluon.
671 
672
673<a name="method57"></a>
674<p/><strong>bool Particle::isDiquark() &nbsp;</strong> <br/>
675true for a diquark or an antidiquark.
676 
677
678<a name="method58"></a>
679<p/><strong>bool Particle::isParton() &nbsp;</strong> <br/>
680true for a gluon, a quark or antiquark up to the b (but excluding top),
681and a diquark or antidiquark consisting of quarks up to the b.
682 
683
684<a name="method59"></a>
685<p/><strong>bool Particle::isHadron() &nbsp;</strong> <br/>
686true for a hadron (made up out of normal quarks and gluons,
687i.e. not for R-hadrons and other exotic states).
688 
689
690<a name="method60"></a>
691<p/><strong>ParticleDataEntry& particleDataEntry() &nbsp;</strong> <br/>
692a reference to the ParticleDataEntry.
693 
694
695<p/>
696Not part of the <code>Particle</code> class proper, but obviously tightly
697linked, are the two methods
698
699<a name="method61"></a>
700<p/><strong>double m(const Particle& pp1, const Particle& pp2) &nbsp;</strong> <br/>
701 
702<strong>double m2(const Particle& pp1, const Particle& pp2) &nbsp;</strong> <br/>
703the (squared) invariant mass of two particles.
704 
705
706<h3>Methods that perform operations</h3>
707
708There are some further methods, some of them inherited from
709<code>Vec4</code>, to modify the properties of a particle.
710They are of little interest to the normal user.
711
712<a name="method62"></a>
713<p/><strong>void Particle::rescale3(double fac) &nbsp;</strong> <br/>
714multiply the three-momentum components by <code>fac</code>.
715 
716
717<a name="method63"></a>
718<p/><strong>void Particle::rescale4(double fac) &nbsp;</strong> <br/>
719multiply the four-momentum components by <code>fac</code>.
720 
721
722<a name="method64"></a>
723<p/><strong>void Particle::rescale5(double fac) &nbsp;</strong> <br/>
724multiply the four-momentum components and the mass by <code>fac</code>.
725 
726
727<a name="method65"></a>
728<p/><strong>void Particle::rot(double theta, double phi) &nbsp;</strong> <br/>
729rotate three-momentum and production vertex by these polar and azimuthal
730angles.
731 
732
733<a name="method66"></a>
734<p/><strong>void Particle::bst(double betaX, double betaY, double betaZ) &nbsp;</strong> <br/>
735boost four-momentum and production vertex by this three-vector.
736 
737
738<a name="method67"></a>
739<p/><strong>void Particle::bst(double betaX, double betaY, double betaZ, double gamma) &nbsp;</strong> <br/>
740as above, but also input the <i>gamma</i> value, to reduce roundoff errors.
741 
742
743<a name="method68"></a>
744<p/><strong>void Particle::bst(const Vec4& pBst) &nbsp;</strong> <br/>
745boost four-momentum and production vertex by
746<i>beta = (px/e, py/e, pz/e)</i>.
747 
748
749<a name="method69"></a>
750<p/><strong>void Particle::bst(const Vec4& pBst, double mBst) &nbsp;</strong> <br/>
751as above, but also use <i>gamma> = e/m</i> to reduce roundoff errors.
752 
753
754<a name="method70"></a>
755<p/><strong>void Particle::bstback(const Vec4& pBst) &nbsp;</strong> <br/>
756 
757<strong>void Particle::bstback(const Vec4& pBst, double mBst) &nbsp;</strong> <br/>
758as above, but with sign of boost flipped.
759 
760
761<a name="method71"></a>
762<p/><strong>void Particle::rotbst(const RotBstMatrix& M) &nbsp;</strong> <br/>
763combined rotation and boost of the four-momentum and production vertex. 
764 
765
766<a name="method72"></a>
767<p/><strong>void Particle::offsetHistory( int minMother, int addMother, int minDaughter, int addDaughter)) &nbsp;</strong> <br/>
768add a positive offset to the mother and daughter indices, i.e.
769if <code>mother1</code> is above <code>minMother</code> then
770<code>addMother</code> is added to it, same with <code>mother2</code>,
771if <code>daughter1</code> is above <code>minDaughter</code> then
772<code>addDaughter</code> is added to it, same with <code>daughter2</code>.
773 
774
775<a name="method73"></a>
776<p/><strong>void Particle::offsetCol( int addCol) &nbsp;</strong> <br/>
777add a positive offset to colour indices, i.e. if <code>col</code> is
778positive then <code>addCol</code> is added to it, same with <code>acol</code>.
779 
780
781<h3>Constructors and operators</h3>
782
783Normally a user would not need to create new particles. However, if
784necessary, the following constructors and methods may be of interest.
785
786<a name="method74"></a>
787<p/><strong>Particle::Particle() &nbsp;</strong> <br/>
788constructs an empty particle, i.e. where all properties have been set 0
789or equivalent.
790 
791
792<a name="method75"></a>
793<p/><strong>Particle::Particle(int id, int status = 0, int mother1 = 0, int mother2 = 0, int daughter1 = 0, int daughter2 = 0, int col = 0, int acol = 0, double px = 0., double py = 0., double pz = 0., double e = 0., double m = 0., double scale = 0., double pol = 9.) &nbsp;</strong> <br/>
794constructs a particle with the input properties provided, and non-provided
795ones set 0 (9 for <code>pol</code>).
796 
797
798<a name="method76"></a>
799<p/><strong>Particle::Particle(int id, int status, int mother1, int mother2, int daughter1, int daughter2, int col, int acol, Vec4 p, double m = 0., double scale = 0., double pol = 9.) &nbsp;</strong> <br/>
800constructs a particle with the input properties provided, and non-provided
801ones set 0 (9 for <code>pol</code>).
802 
803
804<a name="method77"></a>
805<p/><strong>Particle::Particle(const Particle& pt) &nbsp;</strong> <br/>
806constructs an particle that is a copy of the input one.
807 
808
809<a name="method78"></a>
810<p/><strong>Particle& Particle::operator=(const Particle& pt) &nbsp;</strong> <br/>
811copies the input particle.
812 
813
814<a name="method79"></a>
815<p/><strong>void Particle::setPDTPtr() &nbsp;</strong> <br/>
816sets the pointer to the <code>ParticleData</code> objects,
817i.e. to the full particle data table. Also calls <code>setPDEPtr</code>
818below.
819 
820
821<a name="method80"></a>
822<p/><strong>void Particle::setPDEPtr() &nbsp;</strong> <br/>
823sets the pointer to the <code>ParticleDataEntry</code> object of the
824particle, based on its current <code>id</code> code.
825 
826
827<h3>Final notes</h3>
828
829The
830<code><?php $filepath = $_GET["filepath"];
831echo "<a href='EventRecord.php?filepath=".$filepath."' target='page'>";?>Event</a></code>
832class also contains a few methods defined for individual particles,
833but these may require some search in the event record and therefore
834cannot be defined as  <code>Particle</code> methods.
835
836<p/>
837Currently there is no information on polarization states.
838
839</body>
840</html>
841
842<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
843
Note: See TracBrowser for help on using the repository browser.