User defined menu for GSTAR

There are two user menus that can be used for  used for events running. One of them - general menu of advanced Geant interface (AGI) called AGUSER, another one - USER menu is a STAR specific user menu. It is a user choice, which set of commands he will use for simulation. The menu manual can be obtained from during regular staf session  by means of commands:

manual aguser file_name.tex latex         for AGUSER menu or

manual user file_name.tex latex             for  USER menu

You can see the output file, created by means of both above-mentioned commands here. Here we will briefly describe following commands of STAR USER menu: phasespace, momentumbin, skip, udecay, gfdk, secondaries, vxyz, vsig, subevent, shadow and sensecute. Information about track displaying modes can be found at the end of this page.


user/phasespace [ ntrack id ptlow pthigh ylow yhigh philow phihigh ]       Where

ntrack -  Number of tracks per event. Default value is 100.
id       Geant Particle ID. Default value is 8.
ptlow   - Lower limit of pT. Default value is 0.
pthigh - Upper limit of pT. Default value is 1.
ylow    - Lower limit of rapidity. Default value is -1.
yhigh   - Upper limit of rapidity. Default value is 1.
philow  - Lower limit of phi. Default value is 0.
phihigh- Upper limit of phi. Default value is 6.283

By this command one can generate flat phase space in place of input file of events.  Parameters are Geant PID, lower and upper bounds of rapidity interval, lower and upper  bounds of pT interval, and number of tracks per event. Full azimuthal  interval is used.  If no parameters are  given, old values existing in the program are preserved.  Initial limits   are 0< pT<10000, -10<y<+10, 0<phi<2pi.
For example the command line

phasespace 1 8  0.1  1 -1 1

will create one pion  with  randomly chosen pT  in the range  1000 Gev< pT<10000GeV, rapidity in the range +/-1.


user/momentumbin [ntrack id pxlow pxhigh pylow pyhigh pzlow pzhigh ] ,   where

ntrack  - Number of tracks per event.  Default value is 100.
id          - Geant Particle ID. Default value is 8.
pxlow   - Lower limit of px.  Default value is 1.
pxhigh  -Upper limit of px.  Default value is 1.
pylow    -Lower limit of py.  Default value is 1.
pyhigh  - Upper limit of py.  Default value is 1.
pzlow    -Lower limit of pz.  Default value is 1.
pzhigh   -Upper limit of pz.  Default value is 1.

allows generating uniform distribution within given 3-momentum bin in place of  input file of events.  Parameters are Geant PID, lower and upper bounds of   px, py and pz, and number of tracks per event.  If no parameters are given,  100 pi+ will be generated per event, distributed uniformly in the interval     -1<px<1, -1<py<1, -1<pz<1 GeV.  If px_high is less than px_low, then   px_high will be set equal to px_low (i.e. px will have the same value for   all tracks), and similarly for py and pz.

It is possible for some reason to skips few events from the  input event file.  One can use command

user/skip nevent [nsubevent subran1 subran2], where
nevent       - Number of input events to skip.
nsubevent - Number of subevents to skip in first processed event.
subran1     - First random seed at start of first processed subevent.
subran2     - Second random seed at start of first processed subevent.

All default values are equal 0. It skips the next nevent events of input event file. If nsubevent0, skips  first nsubevents subevents in first processed event, using random seeds   subran1 and  subran2. This allows the user to set the seeds to  randomize the   target position correctly at the beginning of the desired event and then   skip directly to any subevent.

Next command
user/udecay pidparent rin rout pid1 pid2 [pid3], where
pidparent  - Geant PID of parent. Default value is 11.
rin                 - Inner limit of radial interval for uniform decay. Default value is 10.
rout          - Outer limit of radial interval for uniform decay. Default value is 100.
pid1          - Geant PID of first decay daughter. Default value is 5.
pid2          - Geant PID of second decay daughter. Default value is 4.
pid3          - Geant PID of third decay daughter, if present. Default value is 0.

initializes parameters for the decay of a particle with uniform probability   along its trajectory between the cylindrical surfaces R=rin and R=rout. This can be used to enhance statistics for the efficiency studies of the  reconstruction of decays. A new particle is defined, having   pidnew=pidparent+200, and which does not have any decay modes defined in  Geant. When particle pidparent appears in the input list of kinematics, its   id is replaced by pidnew. It is propagated from its origin through the
surface R=rout, and then a decay point is chosen uniformly along its trajectory between rin and rout. GSTAR explicitly creates a new vertex at  this decay point, with 100% branching ratio for decay into the two or three  daughters defined, with kinematics defined appropriately (three-body decay assumes scalar particles). Since the path length to the generated vertex  and the parent 4-momentum are known, the appropriate weighting factor for  the vertex due to the lifetime of the parent can be calculated.

There are few more commands that can be useful for different simulation purpose. The command
user/gfdk [ipart] , where ipart     is Geant  PID   (default value is 0)
writes out decay modes for particle id ipart.

user/secondaries scnd , where scnd   is a secondaries treatment flag with default value equals 1,
controls the way how secondary particles are treated:
    0 - secondaries ignored;
    1 - secondaries are put in jstak only (standard)
    2 - some secondaries are saved in KINE bank.
This concerns decay products of particles, already existing in KINE. Other products (than decay) of these particles are saved in KINE only if they are produced in specially named media, which should  be different from the medium, where the parent was born.

user/vxyz  vx  vy  vz,  where
vx  - primary vertex x,
vy  - primary vertex y,
vz  - primary vertex z  (all default values equal 0, possible values can be chosen within the range (-1000,1000 )),

displaces an average position of the interactions vertex in (vx,vy,vz)

user/vsig vsigt vsigz , where
vsigt - transverse vertex spread,
vstgz - longitudinal vertex spread (default values are 0, possible values can be chosen within the range (0,1000 ))

defines sigma if the generated vertex spread both in transverse and longitudinal (along the beam axis) direction.

user/subevent nsub  [ Ntrk_max Nhit_max ]
nsub          - number of final state tracks per sub-event. Default value 200, range (0,10000000).
Ntrk_max  - maximum of tracks per single KINE bank. Default value 64000, range (0,10000000).
Nhit_max   - maximum length of a single HITS bank. Default value 10000000, range (0,10000000).,

controls splitting of full events into a number of smaller sub-events in  the GEANT simulation phase. One important notice:  micky-mouse event generator is not expected to generate splitted events, so one should switch the  splitting off with

subevent 0

user/shadow shdo ,   where   shdo - tracking flag for dense materials (can be 0 or 1, default value is 1),

change the flag value  to set tracking threshold in dense materials very high.  This will prevent showering in magnets and other dense objects, but they will still  block unphysical tracks.

user/sensecute cute, where cute is  electron tracking cut, (can be -1 to 10, default value is -1),
change electron tracking cut in sensitive gases one can control  delta-electron production in detector itself.

Track display

  Tracks can be displayed only in "debug on" mode,  under control of GEANT switches 2, 3 and 4.  Switches relevant to track display:
  swit 2 3  - a GEANT switch for drawing tracks,
  swit 2 0  - to suppress track display even with "debug on",
  swit 2 2  - print tracks step by step,
  swit 4 3  - a GEANT switch to display charged tracks only,
  swit 4 2  - all tracks are displayed.