Page History

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• Beam profile
  • The profile here means the distribution shape of beam protons in X and Y (= R). 
  • When "legacyVtxGen SQ_vtx_gen = true" (or the variable name is "legacyVtxGen" in old versions)
    • The shape is "Gaussian" at "R < 5*sigma" and "1 / R" at "R >= 5*sigma" (cf. https://github.com/E1039-Collaboration/e1039-core/blob/master/generators/E906LegacyVtxGen/SQPrimaryVertexGen.C#L290 )
    • The Gaussian width ("sigma" in cm) is defined by "SIGX_BEAM" and "SIGY_BEAM" in Fun4Sim.C.
    • The Gaussian center is X = Y = 0 cm by default, and can be changed by setting "X_BEAM" and "Y_BEAM";

      rc->set_DoubleFlag("X_BEAM", 0.1); rc->set_DoubleFlag("Y_BEAM", 0.1);

  • When "SQ_vtx_gen = false" (or the variable name is "legacyVtxGen" in old versions)When "legacyVtxGen = false"
    
    • The shape is defined by the following functions of event generators.
    • "set_vertex_distribution_function()" sets the shape to "Uniform" or "Gaussian".
    • "set_vertex_distribution_mean()" sets the mean of the distribution.
    • "set_vertex_distribution_width()" sets the half width in case of "Uniform" or "sigma" in case of "Gaussian".
• Distribution of z-vertex
  • The z-vertex means the position of each generated event in Z.
  • When "legacyVtxGen = true"
    • The distribution shape follows the probability of beam-material interaction, namely the product of beam intensity and material amount at Z, where the beam intensity is attenuated over Z.

    • When "VTX_GEN_MATERIAL_MODE" is set to "Target" (via rc->set_CharFlag("VTX_GEN_MATERIAL_MODE", "Target")), events are generated only on the target material.

    • "VTX_GEN_MATERIAL_MODE" can be set to "Dump" or "TargetDumpGap" to enable only the dump material or the material (i.e. air) in between the target and the dump.
  • When "legacyVtxGen = false"
    • The distribution shape is defined by "set_vertex_distribution_function()" etc. together with the beam profile.
• Target position
  • The z-center and the length of the target is defined by "double target_coil_pos_z" and "double target_l" in Fun4Sim.C (-300 and -7.9 cm by default).
  • "target_z" is the position of the target material relative to the target coils.  It is 0 cm by default.  If you change "target_l", you have to change "target_z" to "0" together, unless you intend to make the relative position non-zero.
  • The x,y-center and the angle of the target are 0 by default.  If you need to change them,

    • Copy "G4_Target.C" to your working directory;

      cp /project/ptgroup/spinquest/core/default/macros/top/G4_Target.C .

      
      

    • Edit your "G4_Target.C" file.
    • Replace #include <top/G4_Target.C> with #include "G4_Target.C" in "Fun4Sim.C".

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