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1<chapter name="Event Information">
2
3<h2>Event Information</h2>
4
5The <code>Info</code> class collects various one-of-a-kind information,
6some relevant for all events and others for the current event.
7An object <code>info</code> is a public member of the <code>Pythia</code>
8class, so if you e.g. have declared <code>Pythia pythia</code>, the
9<code>Info</code> methods can be accessed by
10<code>pythia.info.method()</code>. Most of this is information that
11could also be obtained e.g. from the event record, but is here more
12directly available. It is primarily intended for processes generated
13internally in PYTHIA, but many of the methods would work also for
14events fed in via the Les Houches Accord.
15
16<h3>List information</h3>
17
18<method name="void Info::list()">
19a listing of most of the information set for the current event.
20</method>
21
22<h3>The beams</h3>
23
24<method name="int Info::idA()">
25</method>
26<methodmore name="int Info::idB()">
27the identities of the two beam particles.
28</methodmore>
29
30<method name="double Info::pzA()"> 
31</method>
32<methodmore name="double Info::pzB()">
33the longitudinal momenta of the two beam particles.
34</methodmore>
35
36<method name="double Info::eA()"> 
37</method>
38<methodmore name="double Info::eB()">
39the energies of the two beam particles.
40</methodmore>
41
42<method name="double Info::mA()"> 
43</method>
44<methodmore name="double Info::mB()">
45the masses of the two beam particles.
46</methodmore>
47
48<method name="double Info::eCM()"> 
49</method>
50<methodmore name="double Info::s()">
51the CM energy and its square for the two beams.
52</methodmore>
53
54<h3>Initialization</h3>
55
56<method name="bool Info::tooLowPTmin()">
57normally false, but true if the proposed <ei>pTmin</ei> scale was too low
58in timelike or spacelike showers, or in multiparton interactions. In the
59former case the <ei>pTmin</ei> is raised to some minimal value, in the
60latter the initialization fails (it is impossible to obtain a minijet
61cross section bigger than the nondiffractive one by reducing
62<ei>pTmin</ei>).
63</method>
64
65<h3>The event type</h3>
66
67<method name="string Info::name()"> 
68</method>
69<methodmore name="int Info::code()">
70the name and code of the process that occured.
71</methodmore>
72
73<method name="int Info::nFinal()"> 
74the number of final-state partons in the hard process.
75</method>
76
77<method name="bool Info::isResolved()"> 
78are beam particles resolved, i.e. were PDF's used for the process?
79</method>
80
81<method name="bool Info::isDiffractiveA()"> 
82</method>
83<methodmore name="bool Info::isDiffractiveB()">
84is either beam diffractively excited?
85</methodmore>
86
87<method name="bool Info::isDiffractiveC()"> 
88is there central diffraction (a.k.a. double Pomeron exchange)?
89</method>
90
91<method name="bool Info::isMinBias()"> 
92is the process a minimum-bias one?
93</method>
94
95<method name="bool Info::isLHA()"> 
96has the process been generated from external Les Houches Accord
97information?
98</method>
99
100<method name="bool Info::atEndOfFile()"> 
101true if a linked Les Houches class refuses to return any further
102events, presumably because it has reached the end of the file from
103which events have been read in.
104</method>
105
106<method name="bool Info::hasSub()"> 
107does the process have a subprocess classification?
108Currently only true for minbias and Les Houches events, where it allows
109the hardest collision to be identified.
110</method>
111
112<method name="string Info::nameSub()"> 
113</method>
114<methodmore name="int Info::codeSub()">
115</methodmore>
116<methodmore name="int Info::nFinalSub()">
117the name, code and number of final-state partons in the subprocess
118that occured when <code>hasSub()</code> is true. For a minimum-bias event
119the <code>code</code> would always be 101, while <code>codeSub()</code> 
120would vary depending on the actual hardest interaction, e.g. 111 for
121<ei>g g -> g g</ei>. For a Les Houches event the <code>code</code> would
122always be 9999, while <code>codeSub()</code> would be the external
123user-defined classification code. The methods below would also provide
124information for such particular subcollisions. 
125</methodmore>
126
127<h3>Hard process initiators</h3>
128
129The methods in this sections refer to the two initial partons of the
130hard <ei>2 -> n</ei> process (diffraction excluded; see below).
131
132<method name="int Info::id1()"> 
133</method>
134<methodmore name="int Info::id2()">
135the identities of the two partons coming in to the hard process.
136</methodmore>
137
138<method name="double Info::x1()"> 
139</method>
140<methodmore name="double Info::x2()">
141<ei>x</ei> fractions of the two partons coming in to the hard process.
142</methodmore>
143
144<method name="double Info::y()"> 
145</method>
146<methodmore name="double Info::tau()">
147rapidity and scaled mass-squared of the hard-process subsystem, as
148defined by the above <ei>x</ei> values.
149</methodmore>
150
151<method name="bool Info::isValence1()"> 
152</method>
153<methodmore name="bool Info::isValence2()">
154<code>true</code> if the two hard incoming partons have been picked
155to belong to the valence piece of the parton-density distribution,
156else <code>false</code>. Should be interpreted with caution.
157Information is not set if you switch off parton-level processing.
158</methodmore>
159
160<h3>Hard process parton densities and scales</h3>
161
162The methods in this section refer to the partons for which parton
163densities have been defined, in order to calculate the cross section
164of the hard process (diffraction excluded; see below).
165
166<p/>
167These partons would normally agree with the
168ones above, the initiators of the <ei>2 -> n</ei> process, but it
169does not have to be so. Currently the one counterexample is POWHEG
170events <ref>Ali10</ref>. Here the original hard process could be
171<ei>2 -> (n-1)</ei>. The NLO machinery at times would add an
172initial-state branching to give a <ei>2 -> n</ei> process with a
173changed initial state. In that case the values in this section
174refer to the original <ei>2 -> (n-1)</ei> state and the initiator
175ones above to the complete<ei>2 -> n</ei> process. The
176<code>Info::list()</code> printout will contain a warning in such cases.
177
178<p/>
179For external events in the Les Houches format, the pdf information
180is obtained from the optional <code>#pdf</code> line. When this
181information is absent, the parton identities and <ei>x</ei> values agree
182with the initiator ones above, while the pdf values are unknown and
183therefore set to vanish. The <ei>alpha_s</ei> and <ei>alpha_em</ei>
184values are part of the compulsory information. The factorization and
185renormalization scales are both equated with the one compulsory scale
186value in the Les Houches standard, except when a <code>#pdf</code> 
187line provides the factorization scale separately. If <ei>alpha_s</ei>,
188<ei>alpha_em</ei> or the compulsory scale value are negative at input
189then new values are defined as for internal processes. 
190
191<method name="int Info::id1pdf()"> 
192</method>
193<methodmore name="int Info::id2pdf()">
194the identities of the two partons for which parton density values
195are defined.
196</methodmore>
197
198<method name="double Info::x1pdf()"> 
199</method>
200<methodmore name="double Info::x2pdf()">
201<ei>x</ei> fractions of the two partons for which parton density values
202are defined.
203</methodmore>
204
205<method name="double Info::pdf1()"> 
206</method>
207<methodmore name="double Info::pdf2()">
208parton densities <ei>x*f(x,Q^2)</ei> evaluated for the two incoming
209partons; could be used e.g. for reweighting purposes in conjunction
210with the <code>idpdf</code>, <code>xpdf</code> and <code>QFac</code>
211methods. Events obtained from external programs or files may not
212contain this information and, if so, 0 is returned.
213</methodmore>
214
215<method name="double Info::QFac()"> 
216</method>
217<methodmore name="double Info::Q2Fac()">
218the <ei>Q</ei> or <ei>Q^2</ei> factorization scale at which the
219densities were evaluated.
220</methodmore>
221
222<method name="double Info::alphaS()"> 
223</method>
224<methodmore name="double Info::alphaEM()">
225the <ei>alpha_strong</ei> and <ei>alpha_electromagnetic</ei> values used
226for the hard process.
227</methodmore>
228
229<method name="double Info::QRen()"> 
230</method>
231<methodmore name="double Info::Q2Ren()">
232the <ei>Q</ei> or <ei>Q^2</ei> renormalization scale at which
233<ei>alpha_strong</ei> and <ei>alpha_electromagnetic</ei> were evaluated.
234</methodmore>
235
236<h3>Hard process kinematics</h3>
237
238The methods in this section provide info on the kinematics of the hard
239processes, with special emphasis on <ei>2 -> 2</ei> (diffraction excluded;
240see below).
241
242<method name="double Info::mHat()">
243</method>
244<methodmore name="double Info::sHat()">
245the invariant mass and its square for the hard process.
246</methodmore>
247
248<method name="double Info::tHat()"> 
249</method>
250<methodmore name="double Info::uHat()">
251the remaining two Mandelstam variables; only defined for <ei>2 -> 2</ei>
252processes.
253</methodmore>
254
255<method name="double Info::pTHat()"> 
256</method>
257<methodmore name="double Info::pT2Hat()">
258transverse momentum and its square in the rest frame of a <ei>2 -> 2</ei>
259processes.
260</methodmore>
261
262<method name="double Info::m3Hat()"> 
263</method>
264<methodmore name="double Info::m4Hat()">
265the masses of the two outgoing particles in a <ei>2 -> 2</ei> processes.
266</methodmore>
267
268<method name="double Info::thetaHat()"> 
269</method>
270<methodmore name="double Info::phiHat()">
271the polar and azimuthal scattering angles in the rest frame of
272a <ei>2 -> 2</ei> process.
273</methodmore>
274
275<h3>Diffraction</h3>
276
277Information on the primary elastic or
278<aloc href="Diffraction">diffractive</aloc> process
279(<ei>A B -> A B, X1 B, A X2, X1 X2, A X B</ei>) can be obtained with
280the methods in the "Hard process kinematics" section above. The
281variables here obviously are <ei>s, t, u, ...</ei> rather than
282<ei>sHat, tHat, uHat, ...</ei>, but the method names remain to avoid
283unnecessary duplication. Most other methods are irrelevant for a
284primary elastic/diffractive process.
285
286<p/>Central diffraction <ei>A B -> A X B</ei> is a <ei>2 -> 3</ei>
287process, and therefore most of the <ei>2 -> 2</ei> variables are
288no longer relevant. The <code>tHat()</code> and <code>uHat()</code> 
289methods instead return the two <ei>t</ei> values at the <ei>A -> A</ei> 
290and <ei>B -> B</ei> vertices, and <code>pTHat()</code> the average
291transverse momentum of the three outgoing "particles", while
292<code>thetaHat()</code> and <code>phiHat()</code> are undefined.
293
294<p/>
295While the primary interaction does not contain a hard process,
296the diffractive subsystems can contain them, but need not.
297Specifically, double diffraction can contain two separate hard
298subprocesses, which breaks the methods above. Most of them have been
299expanded with an optional argument to address properties of diffractive
300subsystems. This argument can take four values:
301<ul>
302<li>0 : default argument, used for normal nondiffractive events or
303the primary elastic/diffractive process (see above);
304<li>1 : the <ei>X1</ei> system in single diffraction <ei>A B -> X1 B</ei>
305or double diffraction <ei>A B -> X1 X2</ei>;
306<li>2 : the <ei>X2</ei> system in single diffraction <ei>A B -> A X2</ei>
307or double diffraction <ei>A B -> X1 X2</ei>;
308<li>3 : the <ei>X</ei> system in central diffraction <ei>A B -> A X B</ei>.
309</ul>
310The argument is defined for all of the methods in the three sections above,
311"Hard process initiators", "Hard process parton densities and scales" and
312"Hard process kinematics", with the exception of the <code>isValence</code>
313methods. Also the four final methods of "The event type" section, the
314<code>...Sub()</code> methods, take this argument. But recall that they
315will only provide meaningful answers, firstly if there is a system of the
316requested type, and secondly if there is a hard subprocess in this system.
317A simple check for this is that <code>id1()</code> has to be nonvanishing.
318The methods below this section do not currently provide information
319specific to diffractive subsystems, e.g. the MPI information is not
320bookkept in such cases.   
321
322<h3>Event weight and activity</h3>
323
324<method name="double Info::weight()"> 
325weight assigned to the current event. Is normally 1 and thus
326uninteresting. However, there are several cases where one may have
327nontrivial event weights. These weights must the be used e.g. when
328filling histograms.
329<br/>(i) In the <code><aloc href="PhaseSpaceCuts">
330PhaseSpace:increaseMaximum = off</aloc></code> default strategy,
331an event with a differential cross-section above the assumed one
332(in a given phase-space point) is assigned a weight correspondingly
333above unity. This should happen only very rarely, if at all, and so
334could normally be disregarded.
335<br/>(ii) The <aloc href="UserHooks">User Hooks</aloc> class offers
336the possibility to bias the selection of phase space points, which
337means that events come with a compensating weight, stored here.
338<br/>(iii) For Les Houches events some strategies allow negative weights,
339which then after unweighting lead to events with weight -1. There are
340also Les Houches strategies where no unweighting is done, so events
341come with a weight. Specifically, for strategies <ei>+4</ei> and
342<ei>-4</ei>, the event weight is in units of pb. (Internally in mb,
343but converted at output.)
344</method>
345
346<method name="double Info::weightSum()"> 
347Sum of weights accumulated during the run. For unweighted events this
348agrees with the number of generated events. In order to obtain
349histograms normalized "per event", at the end of a run, histogram
350contents should be divided by this weight. (And additionally
351divided by the bin width.) Normalization to cross section also
352required multiplication by <code>sigmaGen()</code> below.
353</method>
354
355<method name="int Info::lhaStrategy()"> 
356normally 0, but if Les Houches events are input then it gives the
357event weighting strategy, see
358<aloc href="LesHouchesAccord">Les Houches Accord</aloc>.
359</method>
360
361<method name="int Info::nISR()"> 
362</method>
363<methodmore name="int Info::nFSRinProc()">
364</methodmore>
365<methodmore name="int Info::nFSRinRes()">
366the number of emissions in the initial-state showering, in the final-state
367showering excluding resonance decys, and in the final-state showering
368inside resonance decays, respectively.
369</methodmore>
370
371<method name="double Info::pTmaxMPI()"> 
372</method>
373<methodmore name="double Info::pTmaxISR()">
374</methodmore>
375<methodmore name="double Info::pTmaxFSR()">
376Maximum <ei>pT</ei> scales set for MPI, ISR and FSR, given the
377process type and scale choice for the hard interactions. The actual
378evolution will run down from these scales.
379</methodmore>
380
381<method name="double Info::pTnow()">
382The current <ei>pT</ei> scale in the combined MPI, ISR and FSR evolution.
383Useful for classification in <aloc href="UserHooks">user hooks</aloc>,
384but not once the event has been evolved. 
385</method>
386
387<method name="double Info::mergingWeight()"> 
388combined CKKW-L weight assigned to the current event. If CKKW-L merging is
389performed, all histograms should be filled with this weight, as discussed in
390 <a href="MatrixElementMerging.html" target="page"> Matrix Element
391Merging</a>.
392</method>
393
394<h3>Multiparton interactions</h3>
395
396<method name="double Info::a0MPI()">
397The value of a0 when an x-dependent matter profile is used,
398<code>MultipartonInteractions:bProfile = 4</code>.
399</method>
400
401<method name="double Info::bMPI()"> 
402The impact parameter <ei>b</ei> assumed for the current collision when
403multiparton interactions are simulated. Is not expressed in any physical
404size (like fm), but only rescaled so that the average should be unity
405for minimum-bias events (meaning less than that for events with hard
406processes).
407</method>
408
409<method name="double Info::enhanceMPI()"> 
410The choice of impact parameter implies an enhancement or depletion of
411the rate of subsequent interactions, as given by this number. Again
412the average is normalized be unity for minimum-bias events (meaning
413more than that for events with hard processes). 
414</method>
415
416<method name="int Info::nMPI()"> 
417The number of hard interactions in the current event. Is 0 for elastic
418and diffractive events, and else at least 1, with more possible from
419multiparton interactions.
420</method>
421
422<method name="int Info::codeMPI(int i)"> 
423</method>
424<methodmore name="double Info::pTMPI(int i)">
425the process code and transverse momentum of the <code>i</code>'th
426subprocess, with <code>i</code> in the range from 0 to
427<code>nMPI() - 1</code>. The values for subprocess 0 is redundant with
428information already provided above. 
429</methodmore>
430
431<method name="int Info::iAMPI(int i)"> 
432</method>
433<methodmore name="int Info::iBMPI(int i)">
434are normally zero. However, if the <code>i</code>'th subprocess is
435a rescattering, i.e. either or both incoming partons come from the
436outgoing state of previous scatterings, they give the position in the
437event record of the outgoing-state parton that rescatters.
438<code>iAMPI</code> and <code>iBMPI</code> then denote partons coming from
439the first or second beam, respectively.
440</methodmore>
441
442<method name="double Info::eMPI(int i)"> 
443The enhancement or depletion of the rate of the <code>i</code>'th
444subprocess. Is primarily of interest for the
445<code>MultipartonInteractions:bProfile = 4</code> option, where the
446size of the proton depends on the <ei>x</ei> values of the colliding
447partons. Note that <code>eMPI(0) = enhanceMPI()</code>.
448</method>
449
450<h3>Cross sections</h3>
451
452Here are the currently available methods related to the event sample
453as a whole, for the default value <code>i = 0</code>, and otherwise for
454the specific process code provided as argument. This is the number
455obtained with <code>Info::code()</code>, while the further subdivision
456given by <code>Info::codeSub()</code> is not bookkept. While continuously
457updated during the run, it is recommended only to study these properties
458at the end of the event generation, when the full statistics is available.
459The individual process results are not available if
460<aloc href="ASecondHardProcess">a second hard process</aloc> has beeen
461chosen, but can be gleaned from the <code>pythia.stat()</code> output.
462
463<method name="long Info::nTried(int i = 0)">
464</method>
465<methodmore name="long Info::nSelected(int i = 0)">
466</methodmore>
467<methodmore name="long Info::nAccepted(int i = 0)">
468the total number of tried phase-space points, selected hard processes
469and finally accepted events, summed over all allowed processes
470(<code>i = 0</code>) or for the given process.
471The first number is only intended for a study of the phase-space selection
472efficiency. The last two numbers usually only disagree if the user introduces
473some veto during the event-generation process; then the former is the number
474of acceptable events found by PYTHIA and the latter the number that also
475were approved by the user. If you set <aloc href="ASecondHardProcess">a
476second hard process</aloc> there may also be a mismatch.
477</methodmore>
478
479<method name="double Info::sigmaGen(int i = 0)">
480</method>
481<methodmore name="double Info::sigmaErr(int i = 0)">
482the estimated cross section and its estimated error,
483summed over all allowed processes (<code>i = 0</code>) or for the given
484process, in units of mb. The numbers refer to the accepted event sample
485above, i.e. after any user veto.
486</methodmore>
487
488<h3>Loop counters</h3>
489
490Mainly for internal/debug purposes, a number of loop counters from
491various parts of the program are stored in the <code>Info</code> class,
492so that one can keep track of how the event generation is progressing.
493This may be especially useful in the context of the 
494<code><aloc href="UserHooks">User Hooks</aloc></code> facility.
495
496<method name="int Info::getCounter(int i)">
497the method that gives you access to the value of the various loop
498counters.
499<argument name="i"> the counter number you want to access:
500<argoption value="0 - 9"> counters that refer to the run as a whole,
501i.e. are set 0 at the beginning of the run and then only can increase.
502</argoption>
503<argoption value="0"> the number of successful constructor calls for the
504<code>Pythia</code> class (can only be 0 or 1).
505</argoption>
506<argoption value="1"> the number of times a <code>Pythia::init(...)</code>
507call has been begun. 
508</argoption>
509<argoption value="2"> the number of times a <code>Pythia::init(...)</code>
510call has been completed successfully. 
511</argoption>
512<argoption value="3"> the number of times a <code>Pythia::next()</code>
513call has been begun. 
514</argoption>
515<argoption value="4"> the number of times a <code>Pythia::next()</code>
516call has been completed successfully. 
517</argoption>
518<argoption value="10 - 19"> counters that refer to each individual event,
519and are reset and updated in the top-level <code>Pythia::next()</code> 
520method. 
521</argoption>
522<argoption value="10"> the number of times the selection of a new hard
523process has been begun. Normally this should only happen once, unless a
524user veto is set to abort the current process and try a new one.
525</argoption>
526<argoption value="11"> the number of times the selection of a new hard
527process has been completed successfully. 
528</argoption>
529<argoption value="12"> as 11, but additionally the process should
530survive any user veto and go on to the parton- and hadron-level stages.
531</argoption>
532<argoption value="13"> as 11, but additionally the process should
533survive the parton- and hadron-level stage and any user cuts.
534</argoption>
535<argoption value="14"> the number of times the loop over parton- and
536hadron-level processing has begun for a hard process. Is reset each
537time counter 12 above is reached.
538</argoption>
539<argoption value="15"> the number of times the above loop has successfully
540completed the parton-level step.
541</argoption>
542<argoption value="16"> the number of times the above loop has successfully
543completed the checks and user vetoes after the parton-level step.
544</argoption>
545<argoption value="17"> the number of times the above loop has successfully
546completed the hadron-level step.
547</argoption>
548<argoption value="18"> the number of times the above loop has successfully
549completed the checks and user vetoes after the hadron-level step.
550</argoption>
551<argoption value="20 - 39"> counters that refer to a local part of the
552individual event, and are reset at the beginning of this part.
553</argoption>
554<argoption value="20"> the current system being processed in
555<code>PartonLevel::next()</code>. Is almost always 1, but for double
556diffraction the two diffractive systems are 1 and 2, respectively.
557</argoption>
558<argoption value="21"> the number of times the processing of the
559current system (see above) has begun.
560</argoption>
561<argoption value="22"> the number of times a step has begun in the
562combined MPI/ISR/FSR evolution downwards in <ei>pT</ei> 
563for the current system.
564</argoption>
565<argoption value="23"> the number of times MPI has been selected for the
566downwards step above.
567</argoption>
568<argoption value="24"> the number of times ISR has been selected for the
569downwards step above.
570</argoption>
571<argoption value="25"> the number of times FSR has been selected for the
572downwards step above.
573</argoption>
574<argoption value="26">  the number of times MPI has been accepted as the
575downwards step above, after the vetoes.
576</argoption>
577<argoption value="27">  the number of times ISR has been accepted as the
578downwards step above, after the vetoes.
579</argoption>
580<argoption value="28">  the number of times FSR has been accepted as the
581downwards step above, after the vetoes.
582</argoption>
583<argoption value="29"> the number of times a step has begun in the
584separate (optional) FSR evolution downwards in <ei>pT</ei> 
585for the current system.
586</argoption>
587<argoption value="30"> the number of times FSR has been selected for the
588downwards step above.
589</argoption>
590<argoption value="31">  the number of times FSR has been accepted as the
591downwards step above, after the vetoes.
592</argoption>
593<argoption value="40 - 49"> counters that are unused (currently), and
594that therefore are free to use, with the help of the two methods below.
595</argoption>
596</argument>
597</method>
598
599<method name="void Info::setCounter(int i, int value = 0)">
600set the above counters to a given value. Only to be used by you
601for the unassigned counters 40 - 49.
602<argument name="i"> the counter number, see above.
603</argument>
604<argument name="value" default="0"> set the counter to this number;
605normally the default value is what you want.
606</argument>
607</method>
608
609<method name="void Info::addCounter(int i, int value = 0)">
610increase the above counters by a given amount. Only to be used by you
611for the unassigned counters 40 - 49.
612<argument name="i"> the counter number, see above.
613</argument>
614<argument name="value" default="1"> increase the counter by this amount;
615normally the default value is what you want.
616</argument>
617</method>
618
619<h3>Parton shower history</h3>
620
621The following methods are mainly intended for internal use,
622e.g. for matrix-element matching.
623
624<method name="void Info::hasHistory(bool hasHistoryIn)">
625</method>
626<methodmore name="bool Info::hasHistory()">
627set/get knowledge whether the likely shower history of an event
628has been traced.
629</methodmore>
630
631<method name="void Info::zNowISR(bool zNowIn)">
632</method>
633<methodmore name="double Info::zNowISR()">
634set/get value of <ei>z</ei> in latest ISR branching.
635</methodmore>
636
637<method name="void Info::pT2NowISR(bool pT2NowIn)">
638</method>
639<methodmore name="double Info::pT2NowISR()">
640set/get value of <ei>pT^2</ei> in latest ISR branching.
641</methodmore>
642
643<h3>Header information</h3>
644
645A simple string key/value store, mainly intended for accessing
646information that is stored in the header block of Les Houches Event
647(LHE) files. In principle, any <code>LHAup</code> derived class can set
648this header information, which can then be read out later. Although the
649naming convention is arbitrary, in practice, it is dictated by the
650XML-like format of LHE files, see <aloc href="LesHouchesAccord">
651Les Houches Accord</aloc> for more details.
652
653<method name="string Info::header(string key)">
654return the header named <code>key</code>
655</method>
656
657<method name="vector &lt;string&gt; Info::headerKeys()">
658return a vector of all header key names
659</method>
660
661<method name="void Info::setHeader(string key, string val)">
662set the header named <code>key</code> with the contents of <code>val</code>
663</method>
664
665</chapter>
666
667<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
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