1 <chapter name="Master Switches">
3 <h2>Master Switches</h2>
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.
11 The event generation is subdivided into three levels: the process
12 level, the parton level and the hadron level, and flags are grouped
15 <h3>Process Level</h3>
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.
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.
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>.
38 For <code>ProcessLevel:all = on</code> one part of the event generation
39 on this level may be switched off individually:
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.
51 It is possible to stop the generation immediately after the basic
52 process has been selected, see <code>PartonLevel:all</code> below.
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.
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>
71 For <code>PartonLevel:all = on</code> some parts of the event generation
72 on this level may be switched off individually:
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>.
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>.
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.
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.
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.
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
115 It is possible to stop the generation immediately after the parton level
116 has been set up, see <code>HadronLevel:all</code> below.
120 The <code>HadronLevel</code> class administrates the final step of the
121 event generation, wherein the partonic configuration from
122 <code>PartonLevel</code> is hadronized, including string fragmentation
123 and secondary decays.
126 Most of the code in this class itself deals with subdividing the partonic
127 content of the event into separate colour singlets, that can be
128 treated individually by the string fragmentation machinery. When a
129 junction and an antijunction are directly connected, it also breaks
130 the string between the two, so that the topology can be reduced back
131 to two separate one-junction systems, while still preserving the
132 expected particle flow in the junction-junction string region(s).
134 <flag name="HadronLevel:all" default="on">
135 If off then stop the generation after the hard process and
136 parton-level activity has been generated, but before the
141 For <code>HadronLevel:all = on</code> some parts of the event generation
142 on this level may be switched off individually:
144 <flag name="HadronLevel:Hadronize" default="on">
145 Master switch for hadronization; on/off = true/false.
146 Further options are found <aloc href="Fragmentation">here</aloc>.
149 <flag name="HadronLevel:Decay" default="on">
150 Master switch for decays; on/off = true/false.
151 Further options are found <aloc href="ParticleDecays">here</aloc>.
154 <flag name="HadronLevel:BoseEinstein" default="off">
155 Master switch for the simulation of Bose-Einstein effects;
156 on/off = true/false. Further options are found
157 <aloc href="BoseEinsteinEffects">here</aloc>.
164 <!-- Copyright (C) 2008 Torbjorn Sjostrand -->