Master Switches
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.
The event generation is subdivided into three levels: the process
level, the parton level and the hadron level, and flags are grouped
accordingly.
Process Level
The ProcessLevel 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.
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 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 HadronLevel switches. Further details are found
here.
For ProcessLevel:all = on one part of the event generation
on this level may be switched off individually:
flag 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 Z^0, W^+-, t, h^0 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.
It is possible to stop the generation immediately after the basic
process has been selected, see PartonLevel:all below.
PartonLevel
The PartonLevel class administrates the middle step of the
event generation, i.e. the evolution from an input (hard) process from
ProcessLevel, containing a few partons only, to a complete
parton-level configuration to be handed on to HadronLevel.
This step involves the application of initial- and final-state radiation,
multiple interactions and the structure of beam remnants.
flag 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 process record is filled, but the event
one is then not.
For PartonLevel:all = on some parts of the event generation
on this level may be switched off individually:
flag PartonLevel:MI
(default = on)
Master switch for multiple interactions; on/off = true/false.
Further options are found here.
flag PartonLevel:ISR
(default = on)
Master switch for initial-state radiation; on/off = true/false.
Further options are found here.
flag PartonLevel:FSR
(default = on)
Master switch for initial-state radiation; on/off = true/false.
Further options are found here.
If you leave this switch on, the following two switches allow
more detailed control to switch off only parts of the showers.
flag PartonLevel:FSRinProcess
(default = on)
Switch for final-state radiation in association with the hard process
itself; on/off = true/false. In addition PartonLevel:FSR
must be on for these emissions to occur.
flag 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
PartonLevel:FSR must be on for these emissions to occur.
Switching off all the above MI/ISR/FSR switches is not equivalent
to setting PartonLevel:all = off. 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 event record.
It is therefore possible to go on and hadronize the event, if desired.
In the latter case no 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 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
HadronLevel:all = off and Check:event = off.
It is possible to stop the generation immediately after the parton level
has been set up, see HadronLevel:all below.
HadronLevel
The HadronLevel class administrates the final step of the
event generation, wherein the partonic configuration from
PartonLevel is hadronized, including string fragmentation
and secondary decays.
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 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.
For HadronLevel:all = on some parts of the event generation
on this level may be switched off individually:
flag HadronLevel:Hadronize
(default = on)
Master switch for hadronization; on/off = true/false.
Further options are found here.
flag HadronLevel:Decay
(default = on)
Master switch for decays; on/off = true/false.
Further options are found here.
flag HadronLevel:BoseEinstein
(default = off)
Master switch for the simulation of Bose-Einstein effects;
on/off = true/false. Further options are found
here.