Context Navigation

← Previous Revision
Latest Revision
Next Revision →
Blame
Revision Log

AlpgenAndMLM.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: 32.0 KB

Line
1
2	<html>
3	<head>
4	<title>ALPGEN and MLM merging</title>
5	<link rel="stylesheet" type="text/css" href="pythia.css"/>
6	<link rel="shortcut icon" href="pythia32.gif"/>
7	</head>
8	<body>
9
10	<script language=javascript type=text/javascript>
11	function stopRKey(evt) {
12	var evt = (evt) ? evt : ((event) ? event : null);
13	var node = (evt.target) ? evt.target :((evt.srcElement) ? evt.srcElement : null);
14	if ((evt.keyCode == 13) && (node.type=="text"))
15	{return false;}
16	}
17
18	document.onkeypress = stopRKey;
19	</script>
20	<?php
21	if($_POST['saved'] == 1) {
22	if($_POST['filepath'] != "files/") {
23	echo "<font color='red'>SETTINGS SAVED TO FILE</font><br/><br/>"; }
24	else {
25	echo "<font color='red'>NO FILE SELECTED YET.. PLEASE DO SO </font><a href='SaveSettings.php'>HERE</a><br/><br/>"; }
26	}
27	?>
28
29	<form method='post' action='AlpgenAndMLM.php'>
30
31	<h2>ALPGEN and MLM merging</h2>
32
33	This manual page describes the ALPGEN [<a href="Bibliography.php" target="page">Man03</a>] and MLM merging
34	[<a href="Bibliography.php" target="page">Man02</a>] interfaces for PYTHIA 8. While future versions of
35	ALPGEN will be able to write out events in LHEF format, previous
36	versions always output events in an ALPGEN native format (a combination
37	of a ".unw" and a "_unw.par" file). The ALPGEN component of this code
38	contains a reader for this native format (for unweighted events), as
39	well as parameter reading for both ALPGEN native and LHE file formats.
40	Although designed to work together with the MLM component, they are
41	implemented entirely separately and it is possible to use one without
42	the other.
43
44	<p/>
45	It should be noted that all the functionality described here is provided
46	through external routines, and therefore the presence of these features is
47	dependent on the main program being used. This structure allows for the
48	easy extensibility of the merging scheme. The files of interest are located
49	in the <code>examples/</code> subdirectory:
50	<ul>
51	<li>
52	<code>MLMhooks.h</code> : provides a
53	<?php $filepath = $_GET["filepath"];
54	echo "<a href='UserHooks.php?filepath=".$filepath."' target='page'>";?><code>UserHooks</code></a> derived
55	class for performing the MLM merging procedure. All <code>MLM:*</code>
56	options, described below, are implemented in this file. Further
57	technical details of this class are given at the end of this manual
58	page.
59	</li>
60	<li>
61	<code>LHAupAlpgen.h</code> : provides three classes for the reading of
62	ALPGEN event and parameter files. <code>LHAupAlpgen</code> is an
63	<?php $filepath = $_GET["filepath"];
64	echo "<a href='LesHouchesAccord.php?filepath=".$filepath."' target='page'>";?><code>LHAup</code></a> derived
65	class for reading in ALPGEN native format event files.
66	<code>AlpgenPar</code> is a class for the parsing of ALPGEN parameter
67	files, making the information available through a simple interface.
68	<code>AlpgenHooks</code> is a
69	<?php $filepath = $_GET["filepath"];
70	echo "<a href='UserHooks.php?filepath=".$filepath."' target='page'>";?><code>UserHooks</code></a> derived class that
71	provides the <code>Alpgen:*</code> options, described below. Further
72	technical details of these classes are given at the end of this manual
73	page.
74	</li>
75	<li>
76	<code>main32.cc, main32.cmnd</code> : a sample main program and card
77	file showing the usage of the previous two files. It combines the Alpgen
78	and MLM UserHooks classes together, such that the functionality of both
79	is available, and reads in a sample ALPGEN event file while performing
80	the MLM merging procedure. Some commented out sets of options are
81	provided in the card file, which can be activated to try different
82	merging setups.
83	</li>
84	<li>
85	<code>main32.unw, main32_unw.par</code> : an ALPGEN format event and
86	parameter file containing 100 W + 3 jet events. It is not feasible
87	to package large event files with the PYTHIA distribution, but this
88	sample is enough to show the different components in action.
89	</li>
90	</ul>
91
92	<h2>ALPGEN</h2>
93
94	<b>NB: these options are provided by the AlpgenHooks class,
95	which must be loaded for this functionality to be present</b>
96
97	<p/>
98	ALPGEN event files that have been written out in LHEF format should be
99	read in through the normal LHEF machinery
100	(see <?php $filepath = $_GET["filepath"];
101	echo "<a href='BeamParameters.php?filepath=".$filepath."' target='page'>";?>beam parameters</a>). Files in
102	ALPGEN's native format, instead, may be processed using the
103	<code>Alpgen:file</code> option below. When using this option, the
104	ALPGEN parameter file is stored in the PYTHIA Info object under the key
105	<code>AlpgenPar</code>, see the "Header information" section of the
106	<?php $filepath = $_GET["filepath"];
107	echo "<a href='EventInformation.php?filepath=".$filepath."' target='page'>";?>Event Information</a> manual page for
108	more details. Processes not implemented by the PYTHIA 6 interface
109	supplied with ALPGEN are also not implemented here.
110
111	<p/>
112	When reading in ALPGEN native event files, some momenta are shifted by
113	the file reader to ensure energy-momentum conservation. The magnitude of
114	these shifts should be small (around the MeV level in the worst case)
115	and warnings will be produced if they are above a set threshold. A large
116	number of warnings may signify unexpected behaviour and should
117	potentially be investigated. It is also known that certain event
118	classes, for example an event with both light and heavy <i>b</i>
119	quarks may give rise to these warnings.
120
121	<p/>
122	The ALPGEN file reader supports the reading of the event and parameter
123	files in gzip format with file extensions ".unw.gz" and "_unw.par.gz"
124	respectively. This requires the use of external libraries, however, and
125	the <code>README</code> file in the main directory contains instructions
126	on how to enable this.
127
128	<p/>
129	All other <code>Alpgen:*</code> options apply to both LHE and native
130	file formats, and include options to guide the MLM merging procedure
131	based on the parameters that are read in with the events file.
132
133	<br/><br/><table><tr><td><strong>Alpgen:file </td><td></td><td> <input type="text" name="1" value="void" size="20"/>   (<code>default = <strong>void</strong></code>)</td></tr></table>
134	This option is used to read in ALPGEN format event files. Using this option
135	overrides any previously set beam options inside PYTHIA. The path to the
136	files, not including any file extension, should be provided e.g. for input
137	files <i>input_unw.par</i> and <i>input.unw</i>, the value
138	<i>input</i> should be used.
139
140
141	<br/><br/><strong>Alpgen:setMasses</strong> <input type="radio" name="2" value="on" checked="checked"><strong>On</strong>
142	<input type="radio" name="2" value="off"><strong>Off</strong>
143	(<code>default = <strong>on</strong></code>)<br/>
144	When switched on, any particle masses provided by ALPGEN are set in
145	the PYTHIA <?php $filepath = $_GET["filepath"];
146	echo "<a href='ParticleDataScheme.php?filepath=".$filepath."' target='page'>";?>particle database</a>.
147
148
149	<br/><br/><strong>Alpgen:setMLM</strong> <input type="radio" name="3" value="on" checked="checked"><strong>On</strong>
150	<input type="radio" name="3" value="off"><strong>Off</strong>
151	(<code>default = <strong>on</strong></code>)<br/>
152	When switched on, the merging parameters (see below) are set according to
153	the ALPGEN hard process cuts:
154	<ul>
155	<li> <i>MLM:eTjetMin = min(ptjmin + 5., 1.2 * ptjmin), </i> </li>
156	<li> <i>MLM:coneRadius = drjmin, </i>
157	<li> <i>MLM:etaJetMax = etajmax, </i>
158	</ul>
159	where the <code>ptjmin</code>, <code>drjmin</code> and
160	<code>etajmax</code> are the incoming ALPGEN parameters. Note that any
161	existing values of these parameters are overwritten.
162
163
164	<br/><br/><strong>Alpgen:setNjet</strong> <input type="radio" name="4" value="on" checked="checked"><strong>On</strong>
165	<input type="radio" name="4" value="off"><strong>Off</strong>
166	(<code>default = <strong>on</strong></code>)<br/>
167	When switched on, the <code>MLM:nJet</code> parameter (see below) is set
168	to the incoming <code>njet</code> ALPGEN parameter. Note that any
169	existing value of this parameter is overwritten.
170
171
172
173	<h2>MLM Merging</h2>
174
175	<b>NB: these options are provided by the MLMhooks class,
176	which must be loaded for this functionality to be present</b>
177
178	<p/>
179	This section describes the MLM merging interface for PYTHIA 8. The most
180	common reference to the algorithm is [<a href="Bibliography.php" target="page">Man02</a>]. In many respects,
181	however, the implementation provided in the ALPGEN package should be
182	considered the official description of the MLM merging procedure.
183	Although designed primarily to work with events generated with ALPGEN, it
184	can in principle also be used with events from a different source. This
185	should not be done without thought, however, and it is up to the user to
186	understand the details of the algorithm and the implications of using a
187	different hard process generator.
188
189	<p/>
190	A brief description of the MLM procedure, as implemented, is given here.
191	First, either the CellJet or SlowJet jet algorithm is chosen, see the
192	<?php $filepath = $_GET["filepath"];
193	echo "<a href='EventAnalysis.php?filepath=".$filepath."' target='page'>";?>Event Analysis</a> page for more details.
194	Both of these algorithms have an <i>R</i> and <i>etaMax</i>
195	parameter. In addition, CellJet has an <i>eTmin</i> and SlowJet has a
196	<i>pTmin</i> parameter. These are the primary three parameters of the
197	merging procedure, and in practice are set dependent on the cuts applied
198	to the matrix element (ME) generation. We stress that the merging
199	procedure is not tied to the geometry of a specific physical detector,
200	but only to the match between the original partons and the resulting
201	jets, using standard jet algorithms in the phase space region where
202	partons have been generated.
203
204	<p/>
205	ME samples with different jet multiplicities are run through the event
206	generator, and the generation interrupted after parton showers have been
207	applied, but before resonance decays and beam remnants have been
208	processed. Note in particular that top quarks will not yet
209	be decayed, which may lead to slight differences with the PYTHIA 6
210	interface included with the ALPGEN package. In what follows, the
211	hardness measure of jets/partons is taken to be <i>eT</i> when CellJet
212	is used and <i>pT</i> when SlowJet is used. The hard system (ignoring
213	all MPI systems) is then analysed:
214	<ul>
215	<li>
216	The particles in the original matrix element process are sorted into
217	light partons, heavy partons and other particles. For backwards
218	compatibility, a light parton is defined as the set <i>(d, u, s, c,
219	b, g)</i> with zero mass. A heavy parton is defined as the set
220	<i>(c, b, t)</i> with non-zero mass.
221	</li>
222	<li>
223	All particles not originating from the heavy partons or other
224	particles are passed to the jet algorithm and clustered.
225	</li>
226	<li>
227	Clustered jets are matched to the light partons in the original ME
228	process. There are two different methods which can be used:
229	<ul>
230	<li>
231	Method 1: The following is done for each parton, in order
232	of decreasing hardness. The <i>delta R</i> between the parton
233	and all jets is calculated and the smallest value taken. If
234	this is less than the jet <i>R</i> parameter, possibly
235	multiplied by a constant, the jet and parton are considered to
236	match, and the jet is removed from further consideration.
237	Note that for CellJet the <i>delta R</i> measure is in
238	<i>(eta, phi)</i>, while for SlowJet, it is in
239	<i>(y, phi)</i>.
240	</li>
241	<li>
242	Method 2: This method is only possible when using the SlowJet
243	algorithm. Before the clustering is performed, extremely soft
244	"ghost" particles are added to the event at the
245	<i>(y, phi)</i> coordinates of the original matrix element
246	partons. If such a particle is clustered into a jet, the parton
247	and jet are considered to match. The idea of "ghost" particles
248	was originally introduced by FastJet as a way to measure jet
249	areas [<a href="Bibliography.php" target="page">Cac06</a>] and should not affect clustering with an
250	infrared-safe jet algorithm.
251	</li>
252	</ul>
253	<li>
254	If there is a light ME parton remaining which has not been matched
255	to a jet, then the event is vetoed. If all ME partons have been
256	matched to a jet, but there are still some extra jets remaining,
257	then two options are possible:
258	<ul>
259	<li>
260	Exclusive mode: the event is vetoed. This is typically used when
261	there are ME samples with higher jet multiplicities, which would
262	fill in the extra jets.
263	</li>
264	<li>
265	Inclusive mode: the event is retained if the extra jets are softer
266	than the softest matched jet. This is typically used when
267	there is no ME sample with higher jet multiplicity, so the parton
268	shower should be allowed to give extra jets.
269	</ul>
270	</li>
271	<li>
272	All particles originating from the heavy partons are passed to the
273	jet algorithm and clustered.
274	</li>
275	<li>
276	The clustered jets are again matched to the original partons, but
277	there is no requirement for a match to be present; all matched jets
278	are immediately discarded. The matching procedure is much the same
279	as for light partons, but with two differences when <i>delta R</i>
280	matching is used. First, a different <i>R</i> parameter than that
281	used by the jet algorithm may optionally be given. Second, all jets
282	that are within the given radius of the parton are matched, not
283	just the one with the smallest <i>delta R</i> measure. If there
284	are still extra jets remaining then in exclusive mode the event is
285	immediately vetoed, while in inclusive mode the event is retained if
286	the extra jets are softer than the softest <em>light</em> matched jet.
287	</li>
288	</ul>
289
290	<p/>
291	Some different options are provided, specified further below. These
292	are set so that, by default, the algorithm closely follows the official
293	MLM interface provided in the ALPGEN package. All vetoing of events
294	is done through the usual
295	<?php $filepath = $_GET["filepath"];
296	echo "<a href='UserHooks.php?filepath=".$filepath."' target='page'>";?><code>UserHooks</code></a> machinery, and is
297	therefore already taken into account in the cross section.
298	In the output from
299	<code><?php $filepath = $_GET["filepath"];
300	echo "<a href='EventStatistics.php?filepath=".$filepath."' target='page'>";?>Pythia::statistics()</a></code>,
301	the difference between the "Selected" and "Accepted" columns gives the
302	number of events that have not survived the vetoing procedure. It is
303	still the responsibility of the user to add together the results from
304	runs with different jet multiplicities. In the simplest case, when
305	ALPGEN input is used and the hard process parameters are used to guide
306	the merging procedure, it is enough to set the <code>MLM:nJetMax</code>
307	parameter (see below).
308
309
310	<h3>Merging</h3>
311
312	<br/><br/><strong>MLM:merge</strong> <input type="radio" name="5" value="on"><strong>On</strong>
313	<input type="radio" name="5" value="off" checked="checked"><strong>Off</strong>
314	(<code>default = <strong>off</strong></code>)<br/>
315	Master switch to activate MLM merging.
316
317
318
319	<h3>Exclusive mode</h3>
320
321	The following settings determine whether clustered jets which do not
322	match an original hard parton are allowed. They are typically permitted
323	in the highest jet multiplicity sample, where the parton shower may
324	produce extra hard jets, without risk of double counting. Any
325	extra jet produced by the shower must be softer than any matched light
326	jet, or else the event is vetoed.
327
328	<br/><br/><table><tr><td><strong>MLM:exclusive </td><td>   (<code>default = <strong>2</strong></code>; <code>minimum = 0</code>; <code>maximum = 2</code>)</td></tr></table>
329	Exclusive or inclusive merging.
330	<br/>
331	<input type="radio" name="6" value="0"><strong>0 </strong>: The merging is run in inclusive mode. <br/>
332	<input type="radio" name="6" value="1"><strong>1 </strong>: The merging is run in exclusive mode. <br/>
333	<input type="radio" name="6" value="2" checked="checked"><strong>2 </strong>: If <ei>MLM:nJet < MLM:nJetMax</ei>, then the merging is run in exclusive mode, otherwise it is run in inclusive mode. If <ei>MLM:nJetMax < 0</ei> or <ei>MLM:nJet < 0</ei>, then the algorithm defaults to exclusive mode. <br/>
334
335	<modepick name="MLM:nJet" default="-1" min="-1">
336	The number of additional light jets in the incoming process.
337	This is used when <ei>MLM:exclusive = 2</ei>.
338	Note that for ALPGEN input, this value may be automatically set.
339
340	<br/><br/><table><tr><td><strong>MLM:nJetMax </td><td>   (<code>default = <strong>-1</strong></code>; <code>minimum = -1</code>)</td></tr></table>
341	This parameter is used to indicate the maximum number of jets that will be
342	matched. This is used when <ei>MLM:exclusive = 2</ei>.
343	</modepick>
344
345
346	<h3>Jet algorithm</h3>
347
348	The choice of jet algorithm and associated parameters can be adjusted with
349	the settings below. The PYTHIA 8 internal <code>CellJet</code> and
350	<code>SlowJet</code> routines are used, see the
351	<aloc href="EventAnalysis">Event Analysis</aloc> page for more details.
352
353	<modepick name="MLM:jetAlgorithm" default="1" min="1" max="2">
354	The choice of jet algorithm to use when merging against hard partons.
355	<br/>
356	<input type="radio" name="7" value="1"><strong>1 </strong>: The CellJet algorithm.<br/>
357	<input type="radio" name="7" value="2"><strong>2 </strong>: The SlowJet algorithm.<br/>
358
359	<br/><br/><table><tr><td><strong>MLM:nEta </td><td>   (<code>default = <strong>100</strong></code>; <code>minimum = 50</code>)</td></tr></table>
360	Specific to the CellJet algorithm, the number of bins in pseudorapidity.
361	</modepick>
362
363	<modepick name="MLM:nPhi" default="60" min="30">
364	Specific to the CellJet algorithm, the number of bins in phi.
365	</modepick>
366
367	<parm name="MLM:eTseed" default="1.5" min="0.0">
368	Specific to the CellJet algorithm, the minimum <ei>eT</ei> for a cell
369	to be acceptable as the trial center of a jet.
370	</parm>
371
372	<parm name="MLM:eTthreshold" default="0.1">
373	Specific to the CellJet algorithm, cells with <ei>eT < eTthreshold</ei>
374	are completely neglected by the jet algorithm.
375	</parm>
376
377	<modepick name="MLM:slowJetPower" default="-1" min="-1" max="1">
378	The power to use in the SlowJet algorithm.
379	<br/>
380	<input type="radio" name="8" value="-1"><strong>-1 </strong>: The anti-kT algorithm.<br/>
381	<input type="radio" name="8" value="0"><strong>0 </strong>: The Cambridge/Aachen algorithm.<br/>
382	<input type="radio" name="8" value="1"><strong>1 </strong>: The kT algorithm.<br/>
383
384
385	<h3>Merging parameters</h3>
386
387	The following options are the three main parameters for the merging
388	procedure. Although here they are in principle free parameters, they should
389	be heavily influenced by the hard process generation cuts. For ALPGEN
390	input, these values may be set automatically.
391
392	<br/><br/><table><tr><td><strong>MLM:eTjetMin </td><td></td><td> <input type="text" name="9" value="20.0" size="20"/>   (<code>default = <strong>20.0</strong></code>; <code>minimum = 5.0</code>)</td></tr></table>
393	For the CellJet algorithm, this gives the minimum transverse energy
394	inside a cone for a jet to be accepted. For the SlowJet algorithm, this
395	is instead the minimum transverse momentum required for a cluster to be
396	accepted as a jet.
397
398
399	<br/><br/><table><tr><td><strong>MLM:coneRadius </td><td></td><td> <input type="text" name="10" value="0.7" size="20"/>   (<code>default = <strong>0.7</strong></code>; <code>minimum = 0.1</code>)</td></tr></table>
400	For the CellJet algorithm, this gives the size of the cone in (eta, phi)
401	space drawn around the geometric center of the jet. For the SlowJet
402	algorithm, this gives the <i>R</i> parameter.
403
404
405	<br/><br/><table><tr><td><strong>MLM:etaJetMax </td><td></td><td> <input type="text" name="11" value="2.5" size="20"/>   (<code>default = <strong>2.5</strong></code>; <code>minimum = 0.1</code>)</td></tr></table>
406	For both jet algorithms, this defines the maximum pseudorapidity that
407	the detector is assumed to cover. In this context, however, it is tied
408	to the phase space region in which partons have been generated.
409	Specifically, particles within <i>etaJetMax + coneRadius</i> are
410	passed to the jet algorithm, with only jets within <i>etaJetMax</i>
411	retained in the merging.
412
413
414
415	<h3>Jet matching</h3>
416
417	The following parameters control the criteria for matching a clustered jet
418	to a hard parton.
419
420	<br/><br/><table><tr><td><strong>MLM:jetAllow </td><td>   (<code>default = <strong>1</strong></code>; <code>minimum = 1</code>; <code>maximum = 2</code>)</td></tr></table>
421	Controls which particles are clustered by the jet algorithm.
422	<br/>
423	<input type="radio" name="12" value="1" checked="checked"><strong>1 </strong>: This option explicitly disallows top quarks, leptons and photons. All other particle types are passed to the jet algorithm. <br/>
424	<input type="radio" name="12" value="2"><strong>2 </strong>: No extra particles are disallowed. <br/>
425
426	<br/><br/><table><tr><td><strong>MLM:jetMatch </td><td>   (<code>default = <strong>1</strong></code>; <code>minimum = 1</code>; <code>maximum = 2</code>)</td></tr></table>
427	Criteria for matching a clustered jet to a parton.
428	<br/>
429	<input type="radio" name="13" value="1" checked="checked"><strong>1 </strong>: This option can be used with both the CellJet and SlowJet algorithms. The <ei>delta R</ei> between each parton and jet is taken, and the minimal value compared against <ei>MLM:coneMatchLight * MLM:coneRadius</ei> for light jets or <ei>MLM:coneMatchHeavy * MLM:coneRadiusHeavy</ei> for heavy jets. Note that by default <ei>MLM:coneRadiusHeavy = MLM:coneRadius</ei>, see below. If below this value, the parton and jet are considered to match. With CellJet, the <ei>delta R</ei> measure is in <ei>(eta, phi)</ei>, while with SlowJet it is in <ei>(y, phi)</ei>. <br/>
430	<input type="radio" name="13" value="2"><strong>2 </strong>: This option can only be used with the SlowJet algorithm. The hard partons are inserted into the parton level event as "ghost" particles, but at the correct <ei>(y, phi)</ei> position. If this particle is then clustered into a jet, it is considered a match. <br/>
431
432	<br/><br/><table><tr><td><strong>MLM:coneMatchLight </td><td></td><td> <input type="text" name="14" value="1.5" size="20"/>   (<code>default = <strong>1.5</strong></code>; <code>minimum = 0.1</code>)</td></tr></table>
433	The <code>coneMatchLight</code> parameter used when
434	<i>MLM:jetMatch = 1</i>.
435
436
437	<br/><br/><table><tr><td><strong>MLM:coneRadiusHeavy </td><td></td><td> <input type="text" name="15" value="-1.0" size="20"/>   (<code>default = <strong>-1.0</strong></code>)</td></tr></table>
438	The <code>coneRadiusHeavy</code> parameter used when
439	<i>MLM:jetMatch = 1</i>. When assigned a negative value,
440	the value of <code>MLM:coneRadius</code> is used.
441
442
443	<br/><br/><table><tr><td><strong>MLM:coneMatchHeavy </td><td></td><td> <input type="text" name="16" value="1.0" size="20"/>   (<code>default = <strong>1.0</strong></code>; <code>minimum = 0.1</code>)</td></tr></table>
444	The <code>coneMatchHeavy</code> parameter used when
445	<i>MLM:jetMatch = 1</i>.
446
447
448
449	<h2>Class information</h2>
450
451	Some more technical information about the different classes is given
452	below. For clarity, some limited information on certain private methods
453	is provided.
454
455	<h3>LHAupAlpgen</h3>
456
457	This class is derived from the
458	<?php $filepath = $_GET["filepath"];
459	echo "<a href='LesHouchesAccord.php?filepath=".$filepath."' target='page'>";?><code>LHAup</code></a> base class, and
460	uses the standard machinery to pass initialisation and event data to
461	PYTHIA. These standard functions are not documented here. The complete
462	parameter file is stored in the PYTHIA Info object, if given, under the
463	key <code>AlpgenPar</code>.
464
465	<a name="method1"></a>
466	<p/><strong>LHAupAlpgen::LHAupAlpgen(const char baseFNin, Info infoPtrIn = NULL)  </strong> <br/>
467	The constructor for the class takes the base filename for the ALPGEN
468	format files (without file extensions) and optionally a pointer to a
469	PYTHIA Info class, used for warning/error message printing and for
470	storing the ALPGEN parameter file. The event and
471	parameter files are opened immediately, with the <code>AlpgenPar</code>
472	class, described below, used to parse the parameter file.
473
474
475	<a name="method2"></a>
476	<p/><strong>bool LHAupAlpgen::addResonances()  </strong> <br/>
477	This is a private method used when an event is read in. The information
478	read from the event file does not always contain a complete listing of
479	all particles and four-momenta, and so various details must be
480	reconstructed. Exactly which details are filled in can vary based on the
481	ALPGEN process in question.
482
483
484	<a name="method3"></a>
485	<p/><strong>bool LHAupAlpgen::rescaleMomenta()  </strong> <br/>
486	This is another private method used when an event is read in.
487	It shuffles and rescales momenta in an event to ensure energy-momentum
488	conservation. First, <i>pT</i> is made to balance by splitting any
489	imbalance between all outgoing particles with their energies also
490	scaled. Second, the <i>e/pZ</i> of the two incoming particles are
491	scaled to balance the outgoing particles. Finally, any intermediate
492	resonances are recalculated from their decay products.
493
494
495	<h3>AlpgenPar</h3>
496
497	This class parses an ALPGEN parameter file and makes the information
498	available through a simple interface. The information is stored
499	internally in key/value (string/double) format. All lines prior to:
500	<pre> ************** run parameters </pre>
501	are ignored, and in the general case, a line e.g.
502	<pre> 10 3.00000000000000 ! njets</pre>
503	would be stored with key "njets" and value "3.0". The following lines
504	are special cases where the line may be split or the key translated:
505	<pre>
506	3 ! hard process code
507	0.000 4.700 174.300 80.419 91.188 120.000 ! mc,mb,mt,mw,mz,mh
508	912.905 0.0914176 ! Crosssection +- error (pb)
509	100 29787.4 ! unwtd events, lum (pb-1) Njob= 2
510	</pre>
511	In the first line, the key "hard process code" is translated to
512	"hpc". In the second, the mass values are split and each given an entry
513	in the internal store. In the third, the cross section and cross section
514	error are stored under the keys "xsecup" and "xerrup" respectively.
515	Finally, the number of events and luminosity are stored under the keys
516	"nevent" and "lum" respectively. In the event that a duplicate key is
517	present, with differing values, the stored value is overwritten and a
518	warning given.
519
520	<a name="method4"></a>
521	<p/><strong>AlpgenPar::AlpgenPar(Info *infoPtrIn = NULL)  </strong> <br/>
522	The constructor does nothing except for store the PYTHIA Info
523	pointer, if given. This is used for warning/error message printing.
524
525
526	<a name="method5"></a>
527	<p/><strong>bool AlpgenPar::parse(const string paramStr)  </strong> <br/>
528	This method parses an ALPGEN parameter file. The parameter file is
529	passed as a single string, mainly intended to be read out from the
530	PYTHIA Info object using the header information methods.
531
532
533	<a name="method6"></a>
534	<p/><strong>bool AlpgenPar::haveParam(const string &paramIn)  </strong> <br/>
535	Method to check if a parameter with key <code>paramIn</code> is present.
536	Returns true if present, else false.
537
538
539	<a name="method7"></a>
540	<p/><strong>double AlpgenPar::getParam(const string &paramIn)  </strong> <br/>
541
542	<strong>int AlpgenPar::getParamAsInt(const string &paramIn)  </strong> <br/>
543	Return the parameter with key <code>paramIn</code> as a double or
544	integer. The presence of a parameter should have already been checked
545	using the <code>haveParam()</code> function above. If the parameter is
546	not present, 0 is returned.
547
548
549	<a name="method8"></a>
550	<p/><strong>void AlpgenPar::void printParams()  </strong> <br/>
551	Method to print a list of stored parameters.
552
553
554	<h3>AlpgenHooks</h3>
555
556	This <?php $filepath = $_GET["filepath"];
557	echo "<a href='UserHooks.php?filepath=".$filepath."' target='page'>";?><code>UserHooks</code></a> derived class
558	provides all the <code>Alpgen:*</code> options. It is provided as a
559	UserHooks class such that the code works regardless of whether ALPGEN
560	native or LHE file formats are used. It is declared with virtual
561	inheritance so that it may be combine with other UserHooks classes, see
562	the "Combining UserHooks" section below.
563
564	<a name="method9"></a>
565	<p/><strong>AlpgenHooks(Pythia &pythia)  </strong> <br/>
566	The constructor takes a PYTHIA object as input, so that the beam
567	parameter settings can be overridden if the <code>Alpgen:file</code>
568	option is given. If this is the case, an <code>LHAupAlpgen</code>
569	instance is automatically created and passed to PYTHIA.
570
571
572	<a name="method10"></a>
573	<p/><strong>bool initAfterBeams()  </strong> <br/>
574	This is the only UserHooks method that is overridden. It is called
575	directly after PYTHIA has initialised the beams, and therefore the
576	header information should be present in the PYTHIA Info object. The
577	<code>AlpgenPar</code> class is used to parse ALPGEN parameters, if
578	present, which are then used to set further PYTHIA settings.
579
580
581	<h3>MLMhooks</h3>
582
583	This <?php $filepath = $_GET["filepath"];
584	echo "<a href='UserHooks.php?filepath=".$filepath."' target='page'>";?><code>UserHooks</code></a> derived class
585	provides all the <code>MLM:*</code> options. It is also declared with
586	virtual inheritance for combining with other UserHooks classes. It
587	uses standard UserHooks methods to perform the merging procedure
588	outlined previously in this manual page, and therefore detailed method
589	information is not given.
590
591	<h3>Combining UserHooks</h3>
592
593	It is possible to combine multiple UserHooks classes together, such that
594	the functionality of both is present. A prerequisite is that the
595	different UserHooks classes should be declared with virtual inheritance,
596	e.g.
597	<pre>
598	class MLMhooks : virtual public UserHooks
599	</pre>
600	Without this option, when combining two UserHooks derived classes
601	together, two copies of the base UserHooks class would be created
602	leading to ambiguity.
603
604	<p/>
605	An example combining the AlpgenHooks and MLMhooks classes together is
606	given in <code>main32.cc</code>:
607	<pre>
608	class AlpgenAndMLMhooks : public AlpgenHooks, public MLMhooks {
609	public:
610	AlpgenAndMLMhooks(Pythia &pythia)
611	: AlpgenHooks(pythia), MLMhooks() {}
612
613	virtual bool initAfterBeams() {
614	// Call init of both AlpgenHooks and MLMhooks (order important)
615	if (!AlpgenHooks::initAfterBeams()) return false;
616	if (!MLMhooks::initAfterBeams()) return false;
617	return true;
618	}
619	};
620	</pre>
621	This class inherits from both AlpgenHooks and MLMhooks. Any functions
622	which are present in both classes should be overridden with a function
623	that calls the different parent methods in the desired order. In the
624	above example, the only shared methods are the constructor and
625	<code>initAfterBeams()</code>.
626
627	<input type="hidden" name="saved" value="1"/>
628
629	<?php
630	echo "<input type='hidden' name='filepath' value='".$_GET["filepath"]."'/>"?>
631
632	<table width="100%"><tr><td align="right"><input type="submit" value="Save Settings" /></td></tr></table>
633	</form>
634
635	<?php
636
637	if($_POST["saved"] == 1)
638	{
639	$filepath = $_POST["filepath"];
640	$handle = fopen($filepath, 'a');
641
642	if($_POST["1"] != "void")
643	{
644	$data = "Alpgen:file = ".$_POST["1"]."\n";
645	fwrite($handle,$data);
646	}
647	if($_POST["2"] != "on")
648	{
649	$data = "Alpgen:setMasses = ".$_POST["2"]."\n";
650	fwrite($handle,$data);
651	}
652	if($_POST["3"] != "on")
653	{
654	$data = "Alpgen:setMLM = ".$_POST["3"]."\n";
655	fwrite($handle,$data);
656	}
657	if($_POST["4"] != "on")
658	{
659	$data = "Alpgen:setNjet = ".$_POST["4"]."\n";
660	fwrite($handle,$data);
661	}
662	if($_POST["5"] != "off")
663	{
664	$data = "MLM:merge = ".$_POST["5"]."\n";
665	fwrite($handle,$data);
666	}
667	if($_POST["6"] != "2")
668	{
669	$data = "MLM:exclusive = ".$_POST["6"]."\n";
670	fwrite($handle,$data);
671	}
672	if($_POST["7"] != "-1")
673	{
674	$data = "MLM:nJetMax = ".$_POST["7"]."\n";
675	fwrite($handle,$data);
676	}
677	if($_POST["8"] != "100")
678	{
679	$data = "MLM:nEta = ".$_POST["8"]."\n";
680	fwrite($handle,$data);
681	}
682	if($_POST["9"] != "20.0")
683	{
684	$data = "MLM:eTjetMin = ".$_POST["9"]."\n";
685	fwrite($handle,$data);
686	}
687	if($_POST["10"] != "0.7")
688	{
689	$data = "MLM:coneRadius = ".$_POST["10"]."\n";
690	fwrite($handle,$data);
691	}
692	if($_POST["11"] != "2.5")
693	{
694	$data = "MLM:etaJetMax = ".$_POST["11"]."\n";
695	fwrite($handle,$data);
696	}
697	if($_POST["12"] != "1")
698	{
699	$data = "MLM:jetAllow = ".$_POST["12"]."\n";
700	fwrite($handle,$data);
701	}
702	if($_POST["13"] != "1")
703	{
704	$data = "MLM:jetMatch = ".$_POST["13"]."\n";
705	fwrite($handle,$data);
706	}
707	if($_POST["14"] != "1.5")
708	{
709	$data = "MLM:coneMatchLight = ".$_POST["14"]."\n";
710	fwrite($handle,$data);
711	}
712	if($_POST["15"] != "-1.0")
713	{
714	$data = "MLM:coneRadiusHeavy = ".$_POST["15"]."\n";
715	fwrite($handle,$data);
716	}
717	if($_POST["16"] != "1.0")
718	{
719	$data = "MLM:coneMatchHeavy = ".$_POST["16"]."\n";
720	fwrite($handle,$data);
721	}
722	fclose($handle);
723	}
724
725	?>
726	</body>
727	</html>
728
729	<!-- Copyright (C) 2012 Torbjorn Sjostrand -->

Note: See TracBrowser for help on using the repository browser.

Context Navigation

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

Download in other formats: