[u/mrichter/AliRoot.git] / PYTHIA8 / pythia8145 / xmldoc / MasterSwitches.xml

<chapter name="Master Switches">

<h2>Master Switches</h2>

Sometimes it may be convenient to omit certain aspects of the event 
generation chain. This cannot be motivated in a full-blown production
run, but can often be convenient for own understanding and for
debug purposes. The flags on this page allow just that.

<p/>
The event generation is subdivided into three levels: the process
level, the parton level and the hadron level, and flags are grouped
accordingly. 

<h3>Process Level</h3>

The <code>ProcessLevel</code> class administrates the initial step of 
the event generation, wherein the basic process is selected. Currently 
this is done either using some of the internal processes, or with 
Les Houches Accord input.

<p/>
There could not be a complete event without an initial process, so
it would not be a normal action to switch off this step. Furthermore,
without a process set, it is also not possible to carry out the tasks
on the parton level. It is still possible, however, to hadronize 
a parton-level configuration provided by some external program.

<flag name="ProcessLevel:all" default="on">
If off, do not attempt to carry out any generation at all on the 
process or parton level. Do allow parton configurations stored in 
the event record to hadronize and hadrons to decay, however, as set 
by the <code>HadronLevel</code> switches. Further details are found
<aloc href="HadronLevelStandalone">here</aloc>.
</flag> 

<p/>
For <code>ProcessLevel:all = on</code> one part of the event generation 
on this level may be switched off individually: 

<flag name="ProcessLevel:resonanceDecays" default="on">
Master switch to allow resonance decays; on/off = true/false.
Normal hadrons and leptons do not count as resonances, so this is 
aimed specifically towards <ei>Z^0, W^+-, t, h^0</ei> and similar
objects beyond the Standard Model. Do not use this option if you
may produce coloured resonances and intend to allow hadronization,
since currently the program would not know how to handle this.
</flag>

<p/>
It is possible to stop the generation immediately after the basic 
process has been selected, see <code>PartonLevel:all</code> below.

<h3>PartonLevel</h3>

The <code>PartonLevel</code> class administrates the middle step of the 
event generation, i.e. the evolution from an input (hard) process from
<code>ProcessLevel</code>, containing a few partons only, to a complete 
parton-level configuration to be handed on to <code>HadronLevel</code>. 
This step involves the application of initial- and final-state radiation, 
multiple interactions and the structure of beam remnants.

<flag name="PartonLevel:all" default="on">
If off then stop the generation after the hard process has been 
generated, but before the parton-level and hadron-level steps. 
The <code>process</code> record is filled, but the <code>event</code> 
one is then not.
</flag>

<p/>
For <code>PartonLevel:all = on</code> some parts of the event generation 
on this level may be switched off individually: 

<flag name="PartonLevel:MI" default="on">
Master switch for multiple interactions; on/off = true/false.
Further options are found <aloc href="MultipleInteractions">here</aloc>.
</flag>

<flag name="PartonLevel:ISR" default="on">
Master switch for initial-state radiation; on/off = true/false.
Further options are found <aloc href="SpacelikeShowers">here</aloc>.
</flag>

<flag name="PartonLevel:FSR" default="on">
Master switch for initial-state radiation; on/off = true/false.
Further options are found <aloc href="TimelikeShowers">here</aloc>.
If you leave this switch on, the following two switches allow 
more detailed control to switch off only parts of the showers. 
</flag>

<flag name="PartonLevel:FSRinProcess" default="on">
Switch for final-state radiation in association with the hard process 
itself; on/off = true/false. In addition <code>PartonLevel:FSR</code>
must be on for these emissions to occur. 
</flag>

<flag name="PartonLevel:FSRinResonances" default="on">
Master switch for final-state radiation in any resonance decays 
subsequent to the hard process itself; on/off = true/false. In addition 
<code>PartonLevel:FSR</code> must be on for these emissions to occur.
</flag>

<p/>
Switching off all the above MI/ISR/FSR switches is <b>not</b> equivalent 
to setting <code>PartonLevel:all = off</code>. In the former case a 
minimal skeleton of parton-level operations are carried out, such as 
tying together the scattered partons with the beam remnants into colour 
singlets, and storing this information in the <code>event</code> record. 
It is therefore possible to go on and hadronize the event, if desired. 
In the latter case <b>no</b> operations at all are carried out on the 
parton level, and therefore it is also not possible to go on to the 
hadron level.

<flag name="PartonLevel:Remnants" default="on">
Master switch for addition of beam remnants; on/off = true/false.  
Only intended for very special applications, and cannot be used to 
generate complete events. Specifically, unlike the other switches above,
the program will complain and possibly crash unlike you also set 
<code>HadronLevel:all = off</code> and <code>Check:event = off</code>.
</flag>

<p/>
It is possible to stop the generation immediately after the parton level 
has been set up, see <code>HadronLevel:all</code> below.

<h3>HadronLevel</h3>

The <code>HadronLevel</code> class administrates the final step of the 
event generation, wherein the partonic configuration from 
<code>PartonLevel</code> is hadronized, including string fragmentation 
and secondary decays.

<p/>
Most of the code in this class itself deals with subdividing the partonic
content of the event into separate colour singlets, that can be
treated individually by the string fragmentation machinery. When a
junction and an antijunction are directly connected, it also breaks 
the string between the two, so that the topology can be reduced back 
to two separate one-junction systems, while still preserving the
expected particle flow in the junction-junction string region(s).

<flag name="HadronLevel:all" default="on">
If off then stop the generation after the hard process and 
parton-level activity has been generated, but before the 
hadron-level steps.
</flag>

<p/>
For <code>HadronLevel:all = on</code> some parts of the event generation 
on this level may be switched off individually: 

<flag name="HadronLevel:Hadronize" default="on">
Master switch for hadronization; on/off = true/false.
Further options are found <aloc href="Fragmentation">here</aloc>.
</flag>

<flag name="HadronLevel:Decay" default="on">
Master switch for decays; on/off = true/false.
Further options are found <aloc href="ParticleDecays">here</aloc>.
</flag>

<flag name="HadronLevel:BoseEinstein" default="off">
Master switch for the simulation of Bose-Einstein effects; 
on/off = true/false. Further options are found 
<aloc href="BoseEinsteinEffects">here</aloc>.
</flag>


</chapter>

<!-- Copyright (C) 2010 Torbjorn Sjostrand -->
Commit	Line	Data
9419eeef	1	<chapter name="Master Switches">
	2
	3	<h2>Master Switches</h2>
	4
	5	Sometimes it may be convenient to omit certain aspects of the event
	6	generation chain. This cannot be motivated in a full-blown production
	7	run, but can often be convenient for own understanding and for
	8	debug purposes. The flags on this page allow just that.
	9
	10	<p/>
	11	The event generation is subdivided into three levels: the process
	12	level, the parton level and the hadron level, and flags are grouped
	13	accordingly.
	14
	15	<h3>Process Level</h3>
	16
	17	The <code>ProcessLevel</code> class administrates the initial step of
	18	the event generation, wherein the basic process is selected. Currently
	19	this is done either using some of the internal processes, or with
	20	Les Houches Accord input.
	21
	22	<p/>
	23	There could not be a complete event without an initial process, so
	24	it would not be a normal action to switch off this step. Furthermore,
	25	without a process set, it is also not possible to carry out the tasks
	26	on the parton level. It is still possible, however, to hadronize
	27	a parton-level configuration provided by some external program.
	28
	29	<flag name="ProcessLevel:all" default="on">
	30	If off, do not attempt to carry out any generation at all on the
	31	process or parton level. Do allow parton configurations stored in
	32	the event record to hadronize and hadrons to decay, however, as set
	33	by the <code>HadronLevel</code> switches. Further details are found
	34	<aloc href="HadronLevelStandalone">here</aloc>.
	35	</flag>
	36
	37	<p/>
	38	For <code>ProcessLevel:all = on</code> one part of the event generation
	39	on this level may be switched off individually:
	40
	41	<flag name="ProcessLevel:resonanceDecays" default="on">
	42	Master switch to allow resonance decays; on/off = true/false.
	43	Normal hadrons and leptons do not count as resonances, so this is
	44	aimed specifically towards <ei>Z^0, W^+-, t, h^0</ei> and similar
	45	objects beyond the Standard Model. Do not use this option if you
	46	may produce coloured resonances and intend to allow hadronization,
	47	since currently the program would not know how to handle this.
	48	</flag>
	49
	50	<p/>
	51	It is possible to stop the generation immediately after the basic
	52	process has been selected, see <code>PartonLevel:all</code> below.
	53
	54	<h3>PartonLevel</h3>
	55
	56	The <code>PartonLevel</code> class administrates the middle step of the
	57	event generation, i.e. the evolution from an input (hard) process from
	58	<code>ProcessLevel</code>, containing a few partons only, to a complete
	59	parton-level configuration to be handed on to <code>HadronLevel</code>.
	60	This step involves the application of initial- and final-state radiation,
	61	multiple interactions and the structure of beam remnants.
	62
	63	<flag name="PartonLevel:all" default="on">
	64	If off then stop the generation after the hard process has been
65	generated, but before the parton-level and hadron-level steps.
66	The <code>process</code> record is filled, but the <code>event</code>
67	one is then not.
68	</flag>
69
70	<p/>
71	For <code>PartonLevel:all = on</code> some parts of the event generation
72	on this level may be switched off individually:
73
74	<flag name="PartonLevel:MI" default="on">
75	Master switch for multiple interactions; on/off = true/false.
76	Further options are found <aloc href="MultipleInteractions">here</aloc>.
77	</flag>
78
79	<flag name="PartonLevel:ISR" default="on">
80	Master switch for initial-state radiation; on/off = true/false.
81	Further options are found <aloc href="SpacelikeShowers">here</aloc>.
82	</flag>
83
84	<flag name="PartonLevel:FSR" default="on">
85	Master switch for initial-state radiation; on/off = true/false.
86	Further options are found <aloc href="TimelikeShowers">here</aloc>.
87	If you leave this switch on, the following two switches allow
88	more detailed control to switch off only parts of the showers.
89	</flag>
90
91	<flag name="PartonLevel:FSRinProcess" default="on">
92	Switch for final-state radiation in association with the hard process
93	itself; on/off = true/false. In addition <code>PartonLevel:FSR</code>
94	must be on for these emissions to occur.
95	</flag>
96
97	<flag name="PartonLevel:FSRinResonances" default="on">
98	Master switch for final-state radiation in any resonance decays
99	subsequent to the hard process itself; on/off = true/false. In addition
100	<code>PartonLevel:FSR</code> must be on for these emissions to occur.
101	</flag>
102
103	<p/>
104	Switching off all the above MI/ISR/FSR switches is <b>not</b> equivalent
105	to setting <code>PartonLevel:all = off</code>. In the former case a
106	minimal skeleton of parton-level operations are carried out, such as
107	tying together the scattered partons with the beam remnants into colour
108	singlets, and storing this information in the <code>event</code> record.
109	It is therefore possible to go on and hadronize the event, if desired.
110	In the latter case <b>no</b> operations at all are carried out on the
111	parton level, and therefore it is also not possible to go on to the
112	hadron level.
113
114	<flag name="PartonLevel:Remnants" default="on">
115	Master switch for addition of beam remnants; on/off = true/false.
116	Only intended for very special applications, and cannot be used to
117	generate complete events. Specifically, unlike the other switches above,
118	the program will complain and possibly crash unlike you also set
119	<code>HadronLevel:all = off</code> and <code>Check:event = off</code>.
120	</flag>
121
122	<p/>
123	It is possible to stop the generation immediately after the parton level
124	has been set up, see <code>HadronLevel:all</code> below.
125
126	<h3>HadronLevel</h3>
127
128	The <code>HadronLevel</code> class administrates the final step of the
129	event generation, wherein the partonic configuration from
130	<code>PartonLevel</code> is hadronized, including string fragmentation
131	and secondary decays.
132
133	<p/>
134	Most of the code in this class itself deals with subdividing the partonic
135	content of the event into separate colour singlets, that can be
136	treated individually by the string fragmentation machinery. When a
137	junction and an antijunction are directly connected, it also breaks
138	the string between the two, so that the topology can be reduced back
139	to two separate one-junction systems, while still preserving the
140	expected particle flow in the junction-junction string region(s).
141
142	<flag name="HadronLevel:all" default="on">
143	If off then stop the generation after the hard process and
144	parton-level activity has been generated, but before the
145	hadron-level steps.
146	</flag>
147
148	<p/>
149	For <code>HadronLevel:all = on</code> some parts of the event generation
150	on this level may be switched off individually:
151
152	<flag name="HadronLevel:Hadronize" default="on">
153	Master switch for hadronization; on/off = true/false.
154	Further options are found <aloc href="Fragmentation">here</aloc>.
155	</flag>
156
157	<flag name="HadronLevel:Decay" default="on">
158	Master switch for decays; on/off = true/false.
159	Further options are found <aloc href="ParticleDecays">here</aloc>.
160	</flag>
161
162	<flag name="HadronLevel:BoseEinstein" default="off">
163	Master switch for the simulation of Bose-Einstein effects;
164	on/off = true/false. Further options are found
165	<aloc href="BoseEinsteinEffects">here</aloc>.
166	</flag>
167
168
169
170	</chapter>
171
172	<!-- Copyright (C) 2010 Torbjorn Sjostrand -->