1. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 1 r Status of Geant4 in LHCb. r Ideas on how to populate the LHCb Detector Description Data Base (LHCb geometry in Gaudi)

2. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 2 G4 Status è G4 New release (1.0) will be ready in two weeks è G4 in LHCb Linux: Prototype integrating G4 in Gaudi (not included in Gaudi release, used by calorimeter) NT : First NT users of G4. We collaborate in G4 releases. Last G4 release could be compiled with Gaudi on NT because it is not compliant with ISO standard. (It will be before the end of the year, immediately after G4 release).

3. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 3 Towards Complete LHCb Geometry* in Gaudi è Detector Description package is more advanced in new Gaudi release: (Persistency using XML…) è We need to migrate the complete LHCb Geometry to the new format: ( CDF  XML ) I present some ideas on possible ways to get the complete geometry in Gaudi *Geometry means here geometry, materials, parameters...

4. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 4 SICB Gaudi XML files CDF files GEANT3 Recons. Digit. Transient DD Geant 4 Algorithms Visualization Converters

5. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 5 Populating DDDB: Options è Generate XML files from CDF files Every CDF file has a different format. Not all the knowledge is in the CDF files. Translation needs “smart” code, different for each detector. Not a good idea. è Use G3 to G4 tools (in GEANT4): We need a geometry description usable by G4, but also by visualization, reconstruction... Not what we need. è Write XML from Geant3 (?) Could use parts of G3toG4. è Write XML by hand (?) Every option needs sub-detectors experts

6. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 6 G3 to G4 tools. è G3toG4 generates a “G3 call list” file, readable by a G4 application. It includes every Geant3 call with its arguments. è This file can be generated while running your G3 program or from a G3 RZ file. è It also generates the C++ code needed to read this file and create G4 geometry.

7. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 7 G3 to XML  Use G4 tools to create ‘G3 calls list”.  Write interpreter of the “calls list” to write XML. We can use part of the code generated by G3toG4 to read the file. G3 volumes will become logical volumes in the geometry.xml file. We have to take care to avoid duplication of XML code (for different instances of the same volume).  Material definitions can be extracted from material.cdf to write an equivalent xml file.  Logical structure in the store will probably have to be done “by hand” (path to find the detectors in the store…).  Is not more work than writing it from scratch?. It would need some “by hand checks” anyway.  We get exactly the same geometry… Good time to review it?

8. LHCb Software Week 25/11/99 Gonzalo Gracia Abril 8 Tests and first uses of new geometry è Visualization: It is the basic tool to test what we are doing. We need tp write converters from transient objects to objects understandable by the display tool. è GEANT4 Write converters from transient objects to G4 geometry. Check conversion of Physical and logical objects into the corresponding G4 objects.