1. HDGeant4 Development Report major hurdles overcome in geometry geometry validation complete particles now tracking in magnetic field remaining milestones Richard Jones – University of Connecticut GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2013

2. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 2 HDGeant4 project: work plan 1. Download and install a recent stable release of G4 2. Create a template from one of the standard examples 3. Design classes for geometry import from hdds 4. Implement geometry import from hdds 5. Make a set of scripts to generate some standard views of GlueX 6. Debug the hdds geometry and validate using standard views 7. Implement classes for reading and stepping through magnetic fields 8. Configure a robust physics list for GlueX simulations 9. Implement the particle gun event generator 10. Implement Monte Carlo event input from hddm stream 11. Implement and test the internal cobrems generator 12. Create and document standard control macros for a few common scenarios 13. Set up mechanisms for verbose tracking output 14. Implement classes for hits, truth collection and output progress so far (5/2012) slide from collaboration meeting, May 2012

3. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 3 HDGeant4 project: work plan 1. Download and install a recent stable release of G4 2. Create a template from one of the standard examples 3. Design classes for geometry import from hdds 4. Implement geometry import from hdds 5. Make a set of scripts to generate some standard views of GlueX 6. Debug the hdds geometry and validate using standard views 7. Implement classes for reading and stepping through magnetic fields 8. Configure a robust physics list for GlueX simulations 9. Implement the particle gun event generator 10. Implement Monte Carlo event input from hddm stream 11. Implement and test the internal cobrems generator 12. Create and document standard control macros for a few common scenarios 13. Set up mechanisms for verbose tracking output 14. Implement classes for hits, truth collection and output progress so far (5/2012) (9/2013)

4. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 4 HDGeant4 project: work plan 1. Download and install a recent stable release of G4 2. Create a template from one of the standard examples 3. Design classes for geometry import from hdds 4. Implement geometry import from hdds 5. Make a set of scripts to generate some standard views of GlueX 6. Debug the hdds geometry and validate using standard views 7. Implement classes for reading and stepping through magnetic fields 8. Configure a robust physics list for GlueX simulations 9. Implement the particle gun event generator 10. Implement Monte Carlo event input from hddm stream 11. Implement and test the internal cobrems generator 12. Create and document standard control macros for a few common scenarios 13. Set up mechanisms for verbose tracking output 14. Implement classes for hits, truth collection and output progress so far (5/2012) (9/2013)

5. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 5 HDGeant4 : first look with G4 vis slide from collaboration meeting, May 2012

6. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 6 HDGeant4 : first look with G4 vis slide from collaboration meeting, May 2012

7. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 7 HDGeant4 : more cutaway views slide from collaboration meeting, May 2012

8. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 8 HDGeant4 : next steps The geometry has accumulated defects since the original implementation in hdds readout cables from CDC are completely outside of their mother volume! example: readout cables from CDC are completely outside of their mother volume! although the results are affected by them. Geant3 is largely blind to such defects, although the results are affected by them. Geant4 gets very worried by inconsistencies in the geometry – and crashes. time consuming but essential. Next step: work through geometry defects and fix them one by one – time consuming but essential. Remaining steps: 5 – 10 days of work Remaining steps: 5 – 10 days of work slide from collaboration meeting, May 2012

9. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 9 debugging hdds geometry Pretty 3D plots look great! To see real problems, we need to examine planar cuts through the geometry. G4 supports planar cut views through “sectionPlane” view. problems! First look at CDC in transverse cut near upstream end: problems! Same geometry as we are using for geant3 !!! Same geometry as we are using for geant3 !!!  Is this the hdds geometry? check in geant3 dcut view, no!  Is this the hdds geometry renderering in geant4 objects? check, no!  Is this a bug in the geant4 visualization system? major digging, yes!

10. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 10 debugging hdds geometry G4 vis! Vertical sectionPlane: edge-on it should be a zero-thickness line, working for some volumes, not for others at all, still others are cut but shifted…

11. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 11 debugging hdds geometry G4 vis! Careful search through slides by SLAC workshop slides shows admission of problems: standard boolean solid Examination of the G4 visualization code shows that all geometries are treated consistently, using the standard boolean solid logic that is a core component of the G4 geometry. Browsing deep in the visualization code, I see that there are error messages that are suppressed by a compile-time switch in the standard build. Turn in on, rebuild and rerun – many fatal errors reported! “sectionPlane works for some simple geometries, not reliable for more complex geometries.”

12. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 12 debugging G4 vis! page 16 page 52 page 31

13. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 13 debugging G4 vis! … and 3 weeks later, problem found, fix generalized to most general geometry problem resolved, now on to overlaps…

14. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 14 debugging hdds geometry Call CheckOverlaps in G4 3725 violations! first pass: 3725 violations! Many of these are repeats of the same geometry issue, so 95% were straight-forward to solve. Last 5% were difficult: especially the CDC endplates. Several false starts: drill holes for the straws segment the straws (5) parallel worlds parallel worlds  New feature added to Geant4 in version 4.9.5 (2012) parallel layered mass geometries  Given the fancy name “parallel layered mass geometries”  Invented by medical simulation groups to describe human tissue downstream end of CDC with endplate

15. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 15 Layered mass geometries in parallel world Suppose you implement a wooden brick floating on the water. Dig a hole in water… Or, chop a brick into two and place them separately… 15 Geometry IV - M.Asai (SLAC) (slide borrowed from talk by Makoto Asai, SLAC)

16. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 16 Layered mass geometries in parallel worlds Parallel geometry may be stacked on top of mass geometry or other parallel world geometry, allowing a user to define more than one worlds with materials (and region/cuts). Track will see the material of top-layer, if it is null, then one layer beneath. Alternative way of implementing a complicated geometry Rapid prototyping Safer, more flexible and powerful extension of the concept of “many” in Geant3 Safer, more flexible and powerful extension of the concept of “many” in Geant3 Mass worldParallel world 16 Geometry IV - M.Asai (SLAC) (slide borrowed from talk by Makoto Asai, SLAC)

17. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 17 Layered mass geometries in parallel worlds A parallel world may be associated only to some limited types of particles. May define geometries of different levels of detail for different particle types Example for sampling calorimeter: the mass world defines only the crude geometry with averaged material, while a parallel world with all the detailed geometry. Real materials in detailed parallel world geometry are associated with all particle types except e+, e- and gamma. e+, e- and gamma do not see volume boundaries defined in the parallel world, i.e. their steps won’t be limited Shower parameterization such as GFLASH may have its own geometry 17 Geometry IV - M.Asai (SLAC) Geometry seen by e+, e-,  Geometry seen by other particles (slide borrowed from talk by Makoto Asai, SLAC)

18. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 18 debugging hdds geometry - complete new improved model of the straws in the endplate regions – no overlaps flagged!

19. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 19 tracking with particle gun generator Tracking of 10 300 MeV/c protons at ~20° without field (left) and with uniform field (right). Most material has been moved to an “invisible” layer – layers can be turned on/off.

20. Richard Jones, GlueX Collaboration Meeting, Newport News, Oct. 3-5, 2012 20 HDGeant4 status and prospects this fall Still 5 weeks of work before first release – this fall assumes no major new G4 bugs! 50% error – assumes no major new G4 bugs! First release will be alpha – not intended for actual studies! Anticipated ~1 year shake-down transition period. Anticipated ~1 year shake-down transition period. 8 days 1.Implement Monte Carlo event input from hddm stream 8 days 2.Implement and test the internal cobrems generator 3 days 3.Standard control macros for a few common scenarios 1 day 4.Set up mechanisms for verbose tracking output 1 day 5.Implement classes for hits, truth collection and output12 days