Entering a single particle into GEANT

 

This example shows how to enter a single particle into GEANT.

1. Set EOSGX to the proper input mode:

   RUN_MODE DSIM
   INPUT_MODE ONE

2. Enter the particle type (here a gold nucleus):

   PARTICLE 79 197

   In general, Z of the particle is the first argument, and A is the second. If A is -1, then Z is assumed to be the GEANT particle type, so that

   PARTICLE 9 -1

   will enter a .
3. Enter the particle's kinematics using the command

   PKINE VOPT PKIN(1) PKIN(2) PKIN(3) PKCHID

   this command is documented in Section 3.2.

   To enter the particle's kinetic energy per nucleon use PKCHID = ``E'', PKIN(1) = kinetic energy per nucleon (GeV), PKIN(2) = (polar angle), and PKIN(3) = (azimuthal angle), in the volume specified by VOPT. Or to enter the components of the particle's momentum use PKCHID = ``P'', PKIN(1) = , PKIN(2) = , and PKIN(3) = in the volume specified by VOPT.

   Examples:

   PKINE CAVE 0.1 0.0 0.0 E

   specifies a particle of 100 A MeV energy (per nucleon) along the Z axis, and

   PKINE CAVE 0.0 0.0 0.1 P

   specifies a particle of 100 MeV/c momentum along the Z axis.
4. Enter the particle's vertex (or origin):

   ORIGIN TARG

   for the vertex at the center of the target. In general

   ORIGIN CAVE -300.0 0.0 40.0

   will put the vertex at CAVE coordinates -300.0, 0.0, 40.0.
5. Then process the particle - either enter:

   TRIG

   to start the GEANT processing (in NORM mode, see Section 2.2).

   Or, to process the particle, and then send the simulated data to the track finder use:

   GO 1

   In this mode it is assumed that the proper TAS commands have been used to set the proper run mode, disable the TAS hit finder (as required), disable the GEANT hit finder (as required), and enable the ``event loop'' without a data file, as was demonstrated in the example of reading a Monte Carlo data file.