source: HiSusy/trunk/Pythia8/pythia8170/xmldoc/ParticleProperties.xml @ 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: 27.5 KB
Line 
1<chapter name="Particle Properties">
2
3<h2>Particle Properties</h2>
4
5A <code>Particle</code> corresponds to one entry/slot in the
6event record. Its properties therefore is a mix of ones belonging
7to a particle-as-such, like its identity code or four-momentum,
8and ones related to the event-as-a-whole, like which mother it has.
9
10<p/>
11What is stored for each particle is
12<ul>
13<li>the identity code,</li> 
14<li>the status code,</li> 
15<li>two mother indices,</li>
16<li>two daughter indices,</li> 
17<li>a colour and an anticolour index,</li> 
18<li>the four-momentum and mass,</li>
19<li>the scale at which the particle was produced (optional),</li> 
20<li>the polarization/spin/helicity of the particle (optional),</li>
21<li>the production vertex and proper lifetime (optional),</li>
22<li>a pointer to the particle kind in the particle data table, and</li>
23<li>a pointer to the whole particle data table.</li>
24</ul>
25From these, a number of further quantities may be derived.
26
27<h3>Basic output methods</h3>
28
29The following member functions can be used to extract the most important
30information:
31
32<method name="int Particle::id()">
33the identity of a particle, according to the PDG particle codes
34<ref>Yao06</ref>.
35</method>
36
37<method name="int Particle::status()">
38status code. The status code includes information on how a particle was
39produced, i.e. where in the program execution it was inserted into the
40event record, and why. It also tells whether the particle is still present
41or not. It does not tell how a particle disappeared, whether by a decay,
42a shower branching, a hadronization process, or whatever, but this is
43implicit in the status code of its daughter(s). The basic scheme is:
44<ul>
45<li>status = +- (10 * i + j)</li>
46<li> +          : still remaining particles</li>
47<li> -          : decayed/branched/fragmented/... and not remaining</li>
48<li> i =  1 - 9 : stage of event generation inside PYTHIA</li>
49<li> i = 10 -19 : reserved for future expansion</li>
50<li> i >= 20    : free for add-on programs</li>
51<li> j = 1 - 9  : further specification</li>
52</ul>
53In detail, the list of used or foreseen status codes is:
54<ul>
55<li>11 - 19 : beam particles</li> 
56  <ul>
57  <li>11 : the event as a whole</li> 
58  <li>12 : incoming beam</li>
59  <li>13 : incoming beam-inside-beam (e.g. <ei>gamma</ei> 
60           inside <ei>e</ei>)</li>
61  <li>14 : outgoing elastically scattered</li> 
62  <li>15 : outgoing diffractively scattered</li>
63  </ul>
64<li>21 - 29 : particles of the hardest subprocess</li>
65  <ul>
66  <li>21 : incoming</li>
67  <li>22 : intermediate (intended to have preserved mass)</li>
68  <li>23 : outgoing</li>
69  </ul>
70<li>31 - 39 : particles of subsequent subprocesses</li>
71  <ul>
72  <li>31 : incoming</li>
73  <li>32 : intermediate (intended to have preserved mass)</li> 
74  <li>33 : outgoing</li> 
75  <li>34 : incoming that has already scattered</li> 
76  </ul>
77<li>41 - 49 : particles produced by initial-state-showers</li>
78  <ul>
79  <li>41 : incoming on spacelike main branch</li>
80  <li>42 : incoming copy of recoiler</li>
81  <li>43 : outgoing produced by a branching</li>
82  <li>44 : outgoing shifted by a branching</li>
83  <li>45 : incoming rescattered parton, with changed kinematics
84           owing to ISR in the mother system (cf. status 34)</li>
85  <li>46 : incoming copy of recoiler when this is a rescattered
86           parton (cf. status 42)</li>
87  </ul>
88<li>51 - 59 : particles produced by final-state-showers</li>
89  <ul>
90  <li>51 : outgoing produced by parton branching</li>
91  <li>52 : outgoing copy of recoiler, with changed momentum</li> 
92  <li>53 : copy of recoiler when this is incoming parton,
93           with changed momentum</li> 
94  <li>54 : copy of a recoiler, when in the initial state of a
95           different system from the radiator</li>
96  <li>55 : copy of a recoiler, when in the final state of a
97           different system from the radiator</li>
98  </ul>
99<li>61 - 69 : particles produced by beam-remnant treatment</li>
100  <ul>
101  <li>61 : incoming subprocess particle with primordial <ei>kT</ei> 
102           included</li>
103  <li>62 : outgoing subprocess particle with primordial <ei>kT</ei> 
104           included</li>
105  <li>63 : outgoing beam remnant</li> 
106  </ul>
107<li>71 - 79 : partons in preparation of hadronization process</li>
108  <ul>
109  <li>71 : copied partons to collect into contiguous colour singlet</li> 
110  <li>72 : copied recoiling singlet when ministring collapses to
111           one hadron and momentum has to be reshuffled</li>
112  <li>73 : combination of very nearby partons into one</li>
113  <li>74 : combination of two junction quarks (+ nearby gluons)
114           to a diquark</li> 
115  <li>75 : gluons split to decouple a junction-antijunction pair</li> 
116  <li>76 : partons with momentum shuffled to decouple a
117           junction-antijunction pair </li>
118  <li>77 : temporary opposing parton when fragmenting first two
119           strings in to junction (should disappear again)</li>
120  <li>78 : temporary combined diquark end when fragmenting last
121           string in to junction (should disappear again)</li>
122  </ul>
123<li>81 - 89 : primary hadrons produced by hadronization process</li>
124  <ul>
125  <li>81 : from ministring into one hadron</li>
126  <li>82 : from ministring into two hadrons</li>
127  <li>83, 84 : from normal string (the difference between the two
128           is technical, whether fragmented off from the top of the
129           string system or from the bottom, useful for debug only)</li>
130  <li>85, 86 : primary produced hadrons in junction frogmentation of
131           the first two string legs in to the junction,
132           in order of treatment</li>
133  </ul>
134<li>91 - 99 : particles produced in decay process, or by Bose-Einstein
135  effects</li>
136  <ul>
137  <li>91 : normal decay products</li>
138  <li>92 : decay products after oscillation <ei>B0 &lt;-> B0bar</ei> or
139           <ei>B_s0 &lt;-> B_s0bar</ei></li>
140  <li>93, 94 : decay handled by external program, normally
141           or with oscillation</li>
142  <li>99 : particles with momenta shifted by Bose-Einstein effects
143           (not a proper decay, but bookkept as an <ei>1 -> 1</ei> such,
144           happening after decays of short-lived resonances but before
145           decays of longer-lived particles)</li>
146  </ul>
147<li>101 - 109 : particles in the handling of R-hadron production and
148  decay, i.e. long-lived (or stable) particles containing a very heavy
149  flavour</li>
150  <ul>
151  <li>101 : when a string system contains two such long-lived particles,
152            the system is split up by the production of a new q-qbar
153            pair (bookkept as decay chains that seemingly need not conserve
154            flavour etc., but do when considered together)</li>
155  <li>102 : partons rearranged from the long-lived particle end to prepare
156            for fragmentation from this end</li>
157  <li>103 : intermediate "half-R-hadron" formed when a colour octet particle
158            (like the gluino) has been fragmented on one side, but not yet on
159            the other</li>
160  <li>104 : an R-hadron</li>
161  <li>105 : partons or particles formed together with the R-hadron during
162            the fragmentation treatment</li>
163  <li>106 : subdivision of an R-hadron into its flavour content, with
164           momentum split accordingly, in preparation of the decay of
165           the heavy new particle, if it is unstable</li>
166  <li>107 : two temporary leftover gluons joined into one in the formation
167          of a gluino-gluon R-hadron.</li>
168  </ul>
169<li>111 - 199 : reserved for future expansion</li>
170<li>201 - : free to be used by anybody</li>   
171</ul>
172</method>
173
174<method name="int Particle::mother1()">
175</method>
176<methodmore name="int Particle::mother2()">
177the indices in the event record where the first and last mothers are
178stored, if any. There are five allowed combinations of <code>mother1</code> 
179and <code>mother2</code>:
180<ol>
181<li><code>mother1 = mother2 = 0</code>: for lines 0 - 2, where line 0
182represents the event as a whole, and 1 and 2 the two incoming
183beam particles; </li>
184<li><code>mother1 = mother2 > 0</code>: the particle is a "carbon copy"
185of its mother, but with changed momentum as a "recoil"  effect,
186e.g. in a shower;</li>
187<li><code>mother1 > 0, mother2 = 0</code>: the "normal" mother case, where
188it is meaningful to speak of one single mother to several products,
189in a shower or decay;</li>
190<li><code>mother1 &lt; mother2</code>, both > 0, for
191<code>abs(status) = 81 - 86</code>: primary hadrons produced from the
192fragmentation of a string spanning the range from <code>mother1</code> 
193to <code>mother2</code>, so that all partons in this range should be
194considered mothers; and analogously for
195<code>abs(status) = 101 - 106</code>, the formation of R-hadrons;</li>
196<li><code>mother1 &lt; mother2</code>, both > 0, except case 4: particles
197with two truly different mothers, in particular the particles emerging
198from a hard <ei>2 -> n</ei> interaction.</li>
199</ol>   
200<note>Note 1:</note> in backwards evolution of initial-state showers,
201the mother may well appear below the daughter in the event record.
202<note>Note 2:</note> the <code>motherList(i)</code> method of the
203<code>Event</code> class returns a vector of all the mothers,
204providing a uniform representation for all five cases.
205</methodmore>
206
207<method name="int Particle::daughter1()">
208</method>
209<methodmore name="int Particle::daughter2()">
210the indices in the event record where the first and last daughters
211are stored, if any. There are five allowed combinations of
212<code>daughter1</code> and <code>daughter2</code>:
213<ol>
214<li><code>daughter1 = daughter2 = 0</code>: there are no daughters
215(so far);</li>
216<li><code>daughter1 = daughter2 > 0</code>: the particle has a
217"carbon copy" as its sole daughter, but with changed momentum
218as a "recoil" effect, e.g. in a shower;</li> 
219<li><code>daughter1 > 0, daughter2 = 0</code>: each of the incoming beams
220has only (at most) one daughter, namely the initiator parton of the
221hardest interaction; further, in a <ei>2 -> 1</ei> hard interaction,
222like <ei>q qbar -> Z^0</ei>, or in a clustering of two nearby partons,
223the initial partons only have this one daughter;</li> 
224<li><code>daughter1 &lt; daughter2</code>, both > 0: the particle has
225a range of decay products from <code>daughter1</code> to
226<code>daughter2</code>;</li> <li><code>daughter2 &lt; daughter1</code>,
227both > 0: the particle has two separately stored decay products (e.g.
228in backwards evolution of initial-state showers).</li>
229</ol>
230<note>Note 1:</note> in backwards evolution of initial-state showers, the
231daughters may well appear below the mother in the event record.
232<note>Note 2:</note> the mother-daughter relation normally is reciprocal,
233but not always. An example is hadron beams (indices 1 and 2), where each
234beam remnant and the initiator of each multiparton interaction has the
235respective beam as mother, but the beam itself only has the initiator
236of the hardest interaction as daughter.
237<note>Note 3:</note> the <code>daughterList(i)</code> method of the
238<code>Event</code> class returns a vector of all the daughters,
239providing a uniform representation for all five cases. With this method,
240also all the daughters of the beams are caught, with the initiators of
241the basic process given first,  while the rest are in no guaranteed order
242(since they are found by a scanning of the event record for particles
243with the beam as mother, with no further information).
244</methodmore>
245
246<method name="int Particle::col()"> 
247</method>
248<methodmore name="int Particle::acol()"> 
249the colour and anticolour tags, Les Houches Accord <ref>Boo01</ref> 
250style (starting from tag 101 by default, see below).
251<note>Note:</note> in the preliminary implementation of colour sextets
252(exotic BSM particles) that exists since PYTHIA 8.150, a negative
253anticolour tag is interpreted as an additional positive colour tag,
254and vice versa. 
255</methodmore>
256
257<method name="double Particle::px()">
258</method>
259<methodmore name="double Particle::py()">
260</methodmore>
261<methodmore name="double Particle::pz()">
262</methodmore>
263<methodmore name="double Particle::e()">
264the particle four-momentum components.
265</methodmore>
266
267<method name="Vec4 Particle::p()">
268the particle four-momentum vector, with components as above.
269</method>
270
271<method name="double Particle::m()"> 
272the particle mass, stored with a minus sign (times the absolute value)
273for spacelike virtual particles.
274</method>
275
276<method name="double Particle::scale()"> 
277the scale at which a parton was produced, which can be used to restrict
278its radiation to lower scales in subsequent steps of the shower evolution.
279Note that scale is linear in momenta, not quadratic (i.e. <ei>Q</ei>,
280not <ei>Q^2</ei>).
281</method>
282
283<method name="double Particle::pol()"> 
284the polarization/spin/helicity of a particle. Currently Pythia does not
285use this variable for any internal operations, so its meaning is not
286uniquely defined. The LHA standard sets <code>SPINUP</code> to be the
287cosine of the angle between the spin vector and the 3-momentum of the
288decaying particle in the lab frame, i.e. restricted to be between +1
289and -1. A more convenient choice could be the same quantity in the rest
290frame of the particle production, either the hard subprocess or the
291mother particle of a decay. Unknown or unpolarized particles should
292be assigned the value 9.
293</method>
294
295<method name="double Particle::xProd()">
296</method>
297<methodmore name="double Particle::yProd()">
298</methodmore>
299<methodmore name="double Particle::zProd()">
300</methodmore>
301<methodmore name="double Particle::tProd()">
302the production vertex coordinates, in mm or mm/c.
303</methodmore>
304
305<method name="Vec4 Particle::vProd()">
306The production vertex four-vector. Note that the components of a
307<code>Vec4</code> are named <code>px(), py(), pz() and e()</code>
308which of course then should be reinterpreted as above.
309</method>
310
311<method name="double Particle::tau()"> 
312the proper lifetime, in mm/c. It is assigned for all hadrons with
313positive nominal <ei>tau</ei>, <ei>tau_0 > 0</ei>, because it can be used
314by PYTHIA to decide whether a particle should or should not be allowed
315to decay, e.g. based on the decay vertex distance to the primary interaction
316vertex.
317</method>
318
319<h3>Input methods</h3>
320
321The same method names as above are also overloaded in versions that
322set values. These have an input argument of the same type as the
323respective output above, and are of type <code>void</code>.
324
325<p/>
326There are also a few alternative methods for input:
327
328<method name="void Particle::statusPos()">
329</method>
330<methodmore name="void Particle::statusNeg()">
331sets the status sign positive or negative, without changing the absolute value.
332</methodmore>
333
334<method name="void Particle::statusCode(int code)">
335changes the absolute value but retains the original sign.
336</method>
337
338<method name="void Particle::mothers(int mother1, int mother2)">
339sets both mothers in one go.
340</method>
341
342<method name="void Particle::daughters(int daughter1, int daughter2)">
343sets both daughters in one go.
344</method>
345
346<method name="void Particle::cols(int col, int acol)">
347sets both colour and anticolour in one go.
348</method>
349
350<method name="void Particle::p(double px, double py, double pz, double e)">
351sets the four-momentum components in one go.
352</method>
353
354<method name="void Particle::vProd(double xProd, double yProd,
355double zProd, double tProd)">
356sets the production vertex components in one go.
357</method>
358
359<h3>Further output methods</h3>
360
361<p/>
362In addition, a number of derived quantities can easily be obtained,
363but cannot be set, such as:
364
365<method name="int Particle::idAbs()">
366the absolute value of the particle identity code.
367</method>
368
369<method name="int Particle::statusAbs()">
370the absolute value of the status code.
371</method>
372
373<method name="bool Particle::isFinal()">
374true for a remaining particle, i.e. one with positive status code,
375else false. Thus, after an event has been fully generated, it
376separates the final-state particles from intermediate-stage ones.
377(If used earlier in the generation process, a particle then
378considered final may well decay later.) 
379</method>
380
381<method name="bool Particle::isRescatteredIncoming()">
382true for particles with a status code -34, -45, -46 or -54, else false.
383This singles out partons that have been created in a previous
384scattering but here are bookkept as belonging to the incoming state
385of another scattering.
386</method>
387
388<method name="bool Particle::hasVertex()">
389production vertex has been set; if false then production at the origin
390is assumed.
391</method>
392
393<method name="double Particle::m2()">
394squared mass, which can be negative for spacelike partons.
395</method>
396
397<method name="double Particle::mCalc()">
398</method>
399<methodmore name="double Particle::m2Calc()">
400(squared) mass calculated from the four-momentum; should agree
401with <code>m(), m2()</code> up to roundoff. Negative for spacelike
402virtualities.
403</methodmore>
404
405<method name="double Particle::eCalc()">
406energy calculated from the mass and three-momentum; should agree
407with <code>e()</code> up to roundoff. For spacelike partons a
408positive-energy  solution is picked. This need not be the correct
409one, so it is recommended not to use the method in such cases.
410</method>
411
412<method name="double Particle::pT()">
413</method>
414<methodmore name="double Particle::pT2()">
415(squared) transverse momentum.
416</methodmore>
417
418<method name="double Particle::mT()">
419</method>
420<methodmore name="double Particle::mT2()">
421(squared) transverse mass. If <ei>m_T^2</ei> is negative, which can happen
422for a spacelike parton, then <code>mT()</code> returns
423<ei>-sqrt(-m_T^2)</ei>, by analogy with the negative sign used to store
424spacelike masses. 
425</methodmore>
426
427<method name="double Particle::pAbs()">
428</method>
429<methodmore name="double Particle::pAbs2()">
430(squared) three-momentum size.
431</methodmore>
432
433<method name="double Particle::eT()">
434</method>
435<methodmore name="double Particle::eT2()">
436(squared) transverse energy,
437<ei>eT = e * sin(theta) = e * pT / pAbs</ei>.
438</methodmore>
439
440<method name="double Particle::theta()">
441</method>
442<methodmore name="double Particle::phi()">
443polar and azimuthal angle.
444</methodmore>
445
446<method name="double Particle::thetaXZ()">
447angle in the <ei>(p_x, p_z)</ei> plane, between <ei>-pi</ei> and
448<ei>+pi</ei>, with 0 along the <ei>+z</ei> axis
449</method>
450
451<method name="double Particle::pPos()">
452</method>
453<methodmore name="double Particle::pNeg()">
454<ei>E +- p_z</ei>.
455</methodmore>
456
457<method name="double Particle::y()">
458</method>
459<methodmore name="double Particle::eta()">
460rapidity and pseudorapidity.
461</methodmore>
462
463<method name="double Particle::xDec()"> 
464</method>
465<methodmore name="double Particle::yDec()"> 
466</methodmore>
467<methodmore name="double Particle::zDec()"> 
468</methodmore>
469<methodmore name="double Particle::tDec()"> 
470</methodmore>
471<methodmore name="Vec4 Particle::vDec()"> 
472the decay vertex coordinates, in mm or mm/c. This decay vertex is
473calculated from the production vertex, the proper lifetime and the
474four-momentum assuming no magnetic field or other detector interference.
475It can be used to decide whether a decay should be performed or not,
476and thus is defined also for particles which PYTHIA did not let decay.
477</methodmore>
478
479<p/>
480Each Particle contains a pointer to the respective
481<code>ParticleDataEntry</code> object in the
482<aloc href="ParticleDataScheme">particle data tables</aloc>.
483This gives access to properties of the particle species as such. It is
484there mainly for convenience, and should be thrown if an event is
485written to disk, to avoid any problems of object persistency. Should
486an event later be read back in, the pointer will be recreated from the
487<code>id</code> code if the normal input methods are used. (Use the
488<code><aloc href="EventRecord">Event::restorePtrs()</aloc></code> method
489if your persistency scheme bypasses the normal methods.) This pointer is
490used by the following member functions:
491
492<method name="string Particle::name()">
493the name of the particle.
494</method>
495
496<method name="string Particle::nameWithStatus()">
497as above, but for negative-status particles the name is given in
498brackets to emphasize that they are intermediaries.
499</method>
500
501<method name="int Particle::spinType()">
502<ei>2 *spin + 1</ei> when defined, else 0.
503</method>
504
505<method name="double Particle::charge()">
506</method>
507<methodmore name="int Particle::chargeType()">
508charge, and three times it to make an integer.
509</methodmore>
510
511<method name="bool Particle::isCharged()">
512</method>
513<methodmore name="bool Particle::isNeutral()">
514charge different from or equal to 0.
515</methodmore>
516
517<method name="int Particle::colType()">
5180 for colour singlets, 1 for triplets,
519-1 for antitriplets and 2 for octets. (A preliminary implementation of
520colour sextets also exists, using 3 for sextets and -3 for antisextets.)
521</method>
522
523<method name="double Particle::m0()">
524the nominal mass of the particle, according to the data tables.
525</method>
526
527<method name="double Particle::mWidth()">
528</method>
529<methodmore name="double Particle::mMin()"> 
530</methodmore>
531<methodmore name="double Particle::mMax()">
532the width of the particle, and the minimum and maximum allowed mass value
533for particles with a width, according to the data tables.
534</methodmore>
535
536<method name="double Particle::mass()">
537the mass of the particle, picked according to a Breit-Wigner
538distribution for particles with width. It is different each time called,
539and is therefore only used once per particle to set its mass
540<code>m()</code>.
541</method>
542
543<method name="double Particle::constituentMass()">
544will give the constituent masses for quarks and diquarks,
545else the same masses as with <code>m0()</code>.
546</method>
547
548<method name="double Particle::tau0()"> 
549the nominal lifetime <ei>tau_0 > 0</ei>, in mm/c, of the particle species.
550It is used to assign the actual lifetime <ei>tau</ei>.
551</method>
552
553<method name="bool Particle::mayDecay()">
554flag whether particle has been declared unstable or not, offering
555the main user switch to select which particle species to decay.
556</method>
557
558<method name="bool Particle::canDecay()">
559flag whether decay modes have been declared for a particle,
560so that it could be decayed, should that be requested.
561</method>
562
563<method name="bool Particle::doExternalDecay()">
564particles that are decayed by an external program.
565</method>
566
567<method name="bool Particle::isResonance()">
568particles where the decay is to be treated as part of the hard process,
569typically with nominal mass above 20 GeV (<ei>W^+-, Z^0, t, ...</ei>).
570</method>
571
572<method name="bool Particle::isVisible()">
573particles with strong or electric charge, or composed of ones having it, 
574which thereby should be considered visible in a normal detector.
575</method>
576
577<method name="bool Particle::isLepton()">
578true for a lepton or an antilepton (including neutrinos).
579</method>
580
581<method name="bool Particle::isQuark()">
582true for a quark or an antiquark.
583</method>
584
585<method name="bool Particle::isGluon()">
586true for a gluon.
587</method>
588
589<method name="bool Particle::isDiquark()">
590true for a diquark or an antidiquark.
591</method>
592
593<method name="bool Particle::isParton()">
594true for a gluon, a quark or antiquark up to the b (but excluding top),
595and a diquark or antidiquark consisting of quarks up to the b.
596</method>
597
598<method name="bool Particle::isHadron()">
599true for a hadron (made up out of normal quarks and gluons,
600i.e. not for R-hadrons and other exotic states).
601</method>
602
603<method name="ParticleDataEntry& particleDataEntry()">
604a reference to the ParticleDataEntry.
605</method>
606
607<p/>
608Not part of the <code>Particle</code> class proper, but obviously tightly
609linked, are the two methods
610
611<method name="double m(const Particle& pp1, const Particle& pp2)">
612</method>
613<methodmore name="double m2(const Particle& pp1, const Particle& pp2)">
614the (squared) invariant mass of two particles.
615</methodmore>
616
617<h3>Methods that perform operations</h3>
618
619There are some further methods, some of them inherited from
620<code>Vec4</code>, to modify the properties of a particle.
621They are of little interest to the normal user.
622
623<method name="void Particle::rescale3(double fac)">
624multiply the three-momentum components by <code>fac</code>.
625</method>
626
627<method name="void Particle::rescale4(double fac)">
628multiply the four-momentum components by <code>fac</code>.
629</method>
630
631<method name="void Particle::rescale5(double fac)">
632multiply the four-momentum components and the mass by <code>fac</code>.
633</method>
634
635<method name="void Particle::rot(double theta, double phi)">
636rotate three-momentum and production vertex by these polar and azimuthal
637angles.
638</method>
639
640<method name="void Particle::bst(double betaX, double betaY, double betaZ)">
641boost four-momentum and production vertex by this three-vector.
642</method>
643
644<method name="void Particle::bst(double betaX, double betaY, double betaZ,
645double gamma)">
646as above, but also input the <ei>gamma</ei> value, to reduce roundoff errors.
647</method>
648
649<method name="void Particle::bst(const Vec4& pBst)">
650boost four-momentum and production vertex by
651<ei>beta = (px/e, py/e, pz/e)</ei>.
652</method>
653
654<method name="void Particle::bst(const Vec4& pBst, double mBst)">
655as above, but also use <ei>gamma> = e/m</ei> to reduce roundoff errors.
656</method>
657
658<method name="void Particle::bstback(const Vec4& pBst)">
659</method>
660<methodmore name="void Particle::bstback(const Vec4& pBst, double mBst)">
661as above, but with sign of boost flipped.
662</method>
663
664<method name="void Particle::rotbst(const RotBstMatrix& M)">
665combined rotation and boost of the four-momentum and production vertex. 
666</method>
667
668<method name="void Particle::offsetHistory( int minMother, int addMother,
669int minDaughter, int addDaughter))">
670add a positive offset to the mother and daughter indices, i.e.
671if <code>mother1</code> is above <code>minMother</code> then
672<code>addMother</code> is added to it, same with <code>mother2</code>,
673if <code>daughter1</code> is above <code>minDaughter</code> then
674<code>addDaughter</code> is added to it, same with <code>daughter2</code>.
675</method>
676
677<method name="void Particle::offsetCol( int addCol)">
678add a positive offset to colour indices, i.e. if <code>col</code> is
679positive then <code>addCol</code> is added to it, same with <code>acol</code>.
680</method>
681
682<h3>Constructors and operators</h3>
683
684Normally a user would not need to create new particles. However, if
685necessary, the following constructors and methods may be of interest.
686
687<method name="Particle::Particle()">
688constructs an empty particle, i.e. where all properties have been set 0
689or equivalent.
690</method>
691
692<method name="Particle::Particle(int id, int status = 0, int mother1 = 0,
693int mother2 = 0, int daughter1 = 0, int daughter2 = 0, int col = 0,
694int acol = 0, double px = 0., double py = 0., double pz = 0., double e = 0.,
695double m = 0., double scale = 0., double pol = 9.)">
696constructs a particle with the input properties provided, and non-provided
697ones set 0 (9 for <code>pol</code>).
698</method>
699
700<method name="Particle::Particle(int id, int status, int mother1, int mother2,
701int daughter1, int daughter2, int col, int acol, Vec4 p, double m = 0.,
702double scale = 0., double pol = 9.)">
703constructs a particle with the input properties provided, and non-provided
704ones set 0 (9 for <code>pol</code>).
705</method>
706
707<method name="Particle::Particle(const Particle& pt)">
708constructs an particle that is a copy of the input one.
709</method>
710
711<method name="Particle& Particle::operator=(const Particle& pt)">
712copies the input particle.
713</method>
714
715<method name="void Particle::setPDTPtr()">
716sets the pointer to the <code>ParticleData</code> objects,
717i.e. to the full particle data table. Also calls <code>setPDEPtr</code>
718below.
719</method>
720
721<method name="void Particle::setPDEPtr()">
722sets the pointer to the <code>ParticleDataEntry</code> object of the
723particle, based on its current <code>id</code> code.
724</method>
725
726<h3>Final notes</h3>
727
728The
729<code><aloc href="EventRecord">Event</aloc></code> 
730class also contains a few methods defined for individual particles,
731but these may require some search in the event record and therefore
732cannot be defined as  <code>Particle</code> methods.
733
734<p/>
735Currently there is no information on polarization states.
736
737</chapter>
738
739<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
740
Note: See TracBrowser for help on using the repository browser.