Introduced new features in "layer" model:

• • Materials
  • Hit Collection
  • Visualization

•  Materials:

• In the last tagged version (V00-01-09) the sensitive volumes where forty volumes (DL01, DL02, ... , DL40) corresponding to the forty layers in the gas volume.
  The information about crossed materials (mainly crossing the inner cylinder) necessary for the fast tracking algorithm were not stored in the hit.
  It is now inserted a new sensitive volume (DCHI) made of berillium.
  When the particle passes through this volume a singular hit is stored in the hit collection:
   
   

  1,2,3	position	filled
  4,5,6	momentum	filled
  7	layer	0
  8	cell number	-100
  9	particlePDG	filled
  10	track	filled
  11	path	filled
  12	energy loss	filled
  13	number of crossed radiation lengths	filled
  14	distance intersection-wire	-100
  15	intrinsic resolution	-100

   
  You can see that only some of the information are filled with significant values, and that the quantities peculiar of the "layer-volume" (distance intersection-wire, cell ...) are filled with negative values.
  The layer is set 0 because this volume could be considered as the "zero-layer".
   
   

   

• Hit collection:

• During the tracking of the particle the method "processHits" of class BgsDchLayerSD.cc is invoked by G4SteppingManager when a step has started in the sensitive volume. During this method the information are stored in the hit.
  The new code takes into account the possibility of "multi-step" in the same layer or the decay of the particle.
  Before storing the hit in the collection it is necessary to check out if:
   

  1. • the volume in the actual step (B) is different from the one of the preceding step (A);
     • the trackID is the same of the preceding step;
       
       
       
  if these conditions are satisfied then the hit is added to the collection; else if one of these is not satisfied the preceding hit is deleted from the collection and a new hit is collected whose words are:
   
   
   

  #	hit information	step in wich the information is evaluated
  1,2,3	position	B
  4,5,6	momentum	B
  7	layer	B
  8	cell number	B
  9	particlePDG	B
  10	track	B
  11	path	A+B
  12	energy loss	A+B
  13	number of crossed radiation lengths	A+B
  14	distance intersection-wire	B
  15	intrinsic resolution	B

   

   

• Visualization:

• It is now possible to visualize the detector BaBar or only some subdetector using the Geant4 tolls.
  This is an example of the drift chamber visualization: