1 | <chapter name="Master Switches"> |
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2 | |
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3 | <h2>Master Switches</h2> |
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4 | |
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5 | Sometimes it may be convenient to omit certain aspects of the event |
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6 | generation chain. This cannot be motivated in a full-blown production |
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7 | run, but can often be convenient for own understanding and for |
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8 | debug purposes. The flags on this page allow just that. |
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9 | |
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10 | <p/> |
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11 | The event generation is subdivided into three levels: the process |
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12 | level, the parton level and the hadron level, and flags are grouped |
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13 | accordingly. |
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14 | |
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15 | <h3>Process Level</h3> |
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16 | |
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17 | The <code>ProcessLevel</code> class administrates the initial step of |
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18 | the event generation, wherein the basic process is selected. Currently |
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19 | this is done either using some of the internal processes, or with |
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20 | Les Houches Accord input. |
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21 | |
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22 | <p/> |
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23 | There could not be a complete event without an initial process, so |
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24 | it would not be a normal action to switch off this step. Furthermore, |
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25 | without a process set, it is also not possible to carry out the tasks |
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26 | on the parton level. It is still possible, however, to hadronize |
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27 | a parton-level configuration provided by some external program. |
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28 | |
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29 | <flag name="ProcessLevel:all" default="on"> |
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30 | If off, do not attempt to carry out any generation at all on the |
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31 | process level. For the parton level only final-state radiation |
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32 | is possible, using the <code>Pythia::forceTimeShower(...)</code> method. |
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33 | Do allow parton configurations stored in the event record to hadronize |
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34 | and hadrons to decay, however, as set by the <code>HadronLevel</code> |
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35 | switches. Further details are found |
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36 | <aloc href="HadronLevelStandalone">here</aloc>. |
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37 | </flag> |
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38 | |
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39 | <p/> |
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40 | For <code>ProcessLevel:all = on</code> one part of the event generation |
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41 | on this level may be switched off individually: |
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42 | |
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43 | <flag name="ProcessLevel:resonanceDecays" default="on"> |
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44 | Master switch to allow resonance decays; on/off = true/false. |
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45 | Normal hadrons and leptons do not count as resonances, so this is |
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46 | aimed specifically towards <ei>Z^0, W^+-, t, h^0</ei> and similar |
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47 | objects beyond the Standard Model. Do not use this option if you |
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48 | may produce coloured resonances and intend to allow hadronization, |
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49 | since currently the program would not know how to handle this. |
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50 | </flag> |
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51 | |
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52 | <p/> |
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53 | It is possible to stop the generation immediately after the basic |
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54 | process has been selected, see <code>PartonLevel:all</code> below. |
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55 | |
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56 | <h3>PartonLevel</h3> |
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57 | |
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58 | The <code>PartonLevel</code> class administrates the middle step of the |
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59 | event generation, i.e. the evolution from an input (hard) process from |
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60 | <code>ProcessLevel</code>, containing a few partons only, to a complete |
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61 | parton-level configuration to be handed on to <code>HadronLevel</code>. |
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62 | This step involves the application of initial- and final-state radiation, |
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63 | multiparton interactions and the structure of beam remnants. |
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64 | |
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65 | <flag name="PartonLevel:all" default="on"> |
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66 | If off then stop the generation after the hard process has been |
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67 | generated, but before the parton-level and hadron-level steps. |
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68 | The <code>process</code> record is filled, but the <code>event</code> |
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69 | one is then not. |
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70 | </flag> |
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71 | |
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72 | <p/> |
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73 | For <code>PartonLevel:all = on</code> some parts of the event generation |
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74 | on this level may be switched off individually: |
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75 | |
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76 | <flag name="PartonLevel:MPI" default="on"> |
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77 | Master switch for multiparton interactions; on/off = true/false. |
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78 | Further options are found <aloc href="MultipartonInteractions">here</aloc>. |
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79 | </flag> |
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80 | |
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81 | <flag name="PartonLevel:ISR" default="on"> |
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82 | Master switch for initial-state radiation; on/off = true/false. |
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83 | Further options are found <aloc href="SpacelikeShowers">here</aloc>. |
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84 | </flag> |
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85 | |
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86 | <flag name="PartonLevel:FSR" default="on"> |
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87 | Master switch for final-state radiation; on/off = true/false. |
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88 | Further options are found <aloc href="TimelikeShowers">here</aloc>. |
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89 | If you leave this switch on, the following two switches allow |
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90 | more detailed control to switch off only parts of the showers. |
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91 | </flag> |
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92 | |
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93 | <flag name="PartonLevel:FSRinProcess" default="on"> |
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94 | Switch for final-state radiation in association with the hard process |
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95 | itself; on/off = true/false. In addition <code>PartonLevel:FSR</code> |
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96 | must be on for these emissions to occur. |
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97 | </flag> |
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98 | |
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99 | <flag name="PartonLevel:FSRinResonances" default="on"> |
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100 | Master switch for final-state radiation in any resonance decays |
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101 | subsequent to the hard process itself; on/off = true/false. In addition |
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102 | <code>PartonLevel:FSR</code> must be on for these emissions to occur. |
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103 | </flag> |
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104 | |
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105 | <p/> |
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106 | Switching off all the above MPI/ISR/FSR switches is <b>not</b> equivalent |
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107 | to setting <code>PartonLevel:all = off</code>. In the former case a |
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108 | minimal skeleton of parton-level operations are carried out, such as |
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109 | tying together the scattered partons with the beam remnants into colour |
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110 | singlets, and storing this information in the <code>event</code> record. |
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111 | It is therefore possible to go on and hadronize the event, if desired. |
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112 | In the latter case <b>no</b> operations at all are carried out on the |
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113 | parton level, and therefore it is also not possible to go on to the |
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114 | hadron level. |
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115 | |
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116 | <flag name="PartonLevel:Remnants" default="on"> |
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117 | Master switch for addition of beam remnants; on/off = true/false. |
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118 | Only intended for very special applications, and cannot be used to |
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119 | generate complete events. Specifically, unlike the other switches above, |
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120 | the program will complain and possibly crash unlike you also set |
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121 | <code>HadronLevel:all = off</code> and <code>Check:event = off</code>. |
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122 | </flag> |
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123 | |
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124 | <p/> |
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125 | It is possible to stop the generation immediately after the parton level |
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126 | has been set up, see <code>HadronLevel:all</code> below. |
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127 | |
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128 | <h3>HadronLevel</h3> |
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129 | |
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130 | The <code>HadronLevel</code> class administrates the final step of the |
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131 | event generation, wherein the partonic configuration from |
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132 | <code>PartonLevel</code> is hadronized, including string fragmentation |
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133 | and secondary decays. |
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134 | |
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135 | <p/> |
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136 | Most of the code in this class itself deals with subdividing the partonic |
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137 | content of the event into separate colour singlets, that can be |
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138 | treated individually by the string fragmentation machinery. When a |
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139 | junction and an antijunction are directly connected, it also breaks |
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140 | the string between the two, so that the topology can be reduced back |
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141 | to two separate one-junction systems, while still preserving the |
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142 | expected particle flow in the junction-junction string region(s). |
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143 | |
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144 | <flag name="HadronLevel:all" default="on"> |
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145 | If off then stop the generation after the hard process and |
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146 | parton-level activity has been generated, but before the |
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147 | hadron-level steps. |
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148 | </flag> |
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149 | |
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150 | <p/> |
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151 | For <code>HadronLevel:all = on</code> some parts of the event generation |
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152 | on this level may be switched off individually: |
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153 | |
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154 | <flag name="HadronLevel:Hadronize" default="on"> |
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155 | Master switch for hadronization; on/off = true/false. |
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156 | Further options are found <aloc href="Fragmentation">here</aloc>. |
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157 | </flag> |
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158 | |
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159 | <flag name="HadronLevel:Decay" default="on"> |
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160 | Master switch for decays; on/off = true/false. |
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161 | Further options are found <aloc href="ParticleDecays">here</aloc>. |
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162 | </flag> |
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163 | |
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164 | <flag name="HadronLevel:BoseEinstein" default="off"> |
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165 | Master switch for the simulation of Bose-Einstein effects; |
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166 | on/off = true/false. Further options are found |
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167 | <aloc href="BoseEinsteinEffects">here</aloc>. |
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168 | </flag> |
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169 | |
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170 | |
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171 | |
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172 | </chapter> |
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173 | |
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174 | <!-- Copyright (C) 2012 Torbjorn Sjostrand --> |
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