DCH in Bogus using a SuperLayer Model

• 4 Possible approaches for Fast and Full MC in Bogus
  1. 
     
  2. Fast Cylinder Model: Currently available in Bogus (by T. Wenaus). It is a very fast approach: There is only one physical volume per subdetector. Geometrical Transportation is used to propagate the particle through the whole detector with a single step in each subdetector.
     
     
     
     
  3. SuperLayer Model: Currently implemented in Rome by Sh. Rahatlou. It is a first tentative to have a detailed fast MC. Information available at SL level, either in HITS or TRACKS format. (FAST)
     
     
  4. Layer Model: Similar to the SL model but at layer level. (SEMI-FAST)
     
     
  5. Cell Mode: Detailed simulation of the chamber at cell level, with full cell structure currently implemented in DchSimGeom. (FULL)
  
  
  
• First Problems:
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  • What I know about Geant4?
  • What I know about Bogus?
  
  
  
• Why a SuperLayer Model ?
  
  
  • The SuperLayer is the simplest significant physical object to study the chamber physical response
    
    
  • A good exercise to get in touch with G4
  
  
  
• What is in the SuperLayer Model Now?
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  • Same dbio based geometry database, dch.db, currently used in DchSimGeom, to define volumes and materials.
    
    
  • Same volume hierchy as in DchSimGeom:
    1. 
       
       
    2. Dch_phys ----> DCHA in DchSimGeom:
       G4Tubs volume
       
       
    3. Dch_Gas_volume ----> DCHG in DchSimGeom:
       G4Tubs volume
       
       
    4. SupLayTub_phys[0-9] ----> SL01/10 in DchSimGeom:
       
       In Bogus they are defined as G4Tubs while in BBSIM we use the HYPE volume. This is due to the fact that no such volume is now available in GEANT4 Alpha release.
       
       Then the radius values used are those referred to Z=0 in the chamber frame.
  
  
  
  
• What does it do now?
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  • Geometrical Transportation tested with geantinos and electrons. No physical process added yet.
    
    
  • Here is a typical detailed output:
    (/tracking/verbose=4, /event/verbose=4)
    
    
  
  
  
• How it was implemented?
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  • All SuperLayer volumes defined in BgsDchSuperLayer class, and added to "Dch_phys" logical volume:
    
    _lvol->AddDaughter( _SupLayTub_phys[i]);
    
    
  • You can switch from Fast Cylinder to SuperLayer at initialization level:
    
    desc->dchDescription()->selectModel("fast-cylinder");
    desc->dchDescription()->selectModel("superlayer");
    
    In the future you may switch between the models at Run Time Level using a G4UIManager class based object.
    
    
  
  
  
• Which information are available now?
  
  Defined a DchSteppingAction class based on G4UserSteppingAction.
  Once the particle enters/exits a SuperLayer it saves useful information such as position, momentum, direction, step and dE by the following calls:
  
  
  • GetSteppingManager->GetTrack-> GetPosition.x()/y()/z()
    
  • GetSteppingManager->GetTrack-> GetMomentumDirection.x()/y()/z()
    
  • GetSteppingManager->GetStep-> GetDeltaEnergy
    
  • GetSteppingManager->GetTrack-> GetTrueTrackLength()
  
  
  
• What may be done?
  
  We may either define sensitive volumes to be the SuperLayers and have a HIT Structure similar to the one now in DchSimGeom
  
  OR
  
  define some TRACK object at the entering/exit point in/from the SuperLayer.
  
  
  Then we need good parameterisations in each SuperLayer, for example for dE/dx.
  
  
• What misses?
  1. 
     
  2. Hype volumes to define correctly the SuperLayers
     
     
  3. Parameterisations