The New ROOT Geometry Package

1. The New ROOTGeometry Package ACAT2002 Moscow 24 June René Brun, Andrei & Mihaela Gheata CERN ROOT Geometry PackageL

2. Simulation tools Geant3 created in 1981 Still used by the majority of experiments Geant4 A huge investment Slow penetration in experiments Fluka State of the art for hadronics and neutron physics ROOT Geometry Package

3. Detector Geometry (way 1) Simulation program Geant4-based C++ classes Geant4 geometry Visualisation XML files Reconstruction program MySQL ROOT Geometry Package

4. The Virtual MonteCarlo For example AliRoot in Alice DAQ Online This strategy facilitates migration or comparisons with a common input and a common output Geant3 Kinematics Geometry Geant4 Fluka TVirtualMC Geant3.tar.gz includes an upgraded Geant3 with a C++ interface Hits, Digits Geant4_mc.tar.gz includes the TVirtualMC <-->Geant4 interface classes ROOT Geometry Package

5. Virtual MC example (with G3) { // Load basic libraries gSystem->Load("libPhysics"); gSystem->Load("libMC"); gSystem->Load("$(MCINSTALL)/lib/Linux-g++/libexample01"); // Load Geant3 libraries // … skipped // MC application Ex01MCApplication* appl = new Ex01MCApplication("Example01", "The example01 MC application"); appl->InitMC("g3Config.C"); appl->RunMC(1); } void Config() g3Config.C { cout << "Create geant3" << endl; new TGeant3("C++ Interface to Geant3"); } ROOT Geometry Package

6. Virtual MC example (with G4) { // Load basic libraries gSystem->Load("libPhysics"); gSystem->Load("libMC"); gSystem->Load("$(MCINSTALL)/lib/Linux-g++/libexample01"); // Load Geant4 libraries // … skipped // MC application Ex01MCApplication* appl = new Ex01MCApplication("Example01", "The example01 MC application"); appl->InitMC("g4Config.C"); appl->RunMC(1); } void Config() { g4Config.C // RunConfiguration for Geant4 TG4RunConfiguration* runConfiguration = new TG4RunConfiguration(); // TGeant4 new TGeant4("TGeant4", "The Geant4 Monte Carlo", runConfiguration); } ROOT Geometry Package

7. Detector Geometry (way 2) Modelling Visualisation Interactivity Where am I? Distance to boundary Closest boundary Persistency Simulation program Geant3-based Geant4-based Fluka-based C++ classes Geometry package MySQL Reconstruction program Visualisation ROOT Geometry Package

8. The new ROOT Geometry package • Was the request Nr 1 at ROOT FNAL workshop in June 2001 • The package is being developed in collaboration with Alice (Andrei & Mihaela Gheata) • Alpha release in July • faster than Geant3 • Import from Geant3 (eg 4 LHC detectors) • Interfaces to Geant3,4, Fluka in view • Demos on request ROOT Geometry Package

9. The TGeo classes in htmlhttp://pcbrun.cern.ch/geo/ClassIndex.html ROOT Geometry Package

10. TGeoManager ROOT Geometry Package

11. TGeoShape ROOT Geometry Package

12. TGeoVolume ROOT Geometry Package

13. TGeoNode ROOT Geometry Package

14. Example ROOT Geometry Package

15. Automatic conversion from Geant3 Zebra memory Data structure JVOLUM JMATE,etc Root > .x mygeom.C Mygeom.c void gexam1() {TGeoMaterial *mat; TGeoMixture *mix; TGeoManager *gexam1 = new TGeoManager("gexam1","gexam1.C"); //-----------List of Materials and Mixtures-------------- mat = new TGeoMaterial("mat9","ALUMINIUM",26.98,13,2.7); mix = new TGeoMixture("mix10","IRON(COMPOUND)",3); mix->DefineElement(0,55.847,26,0.703964); mix->DefineElement(1,58.71,28,0.9900000E-01); mix->DefineElement(2,51.998,24,0.197); mat = new TGeoMaterial("mat11","COPPER",63.54,29,8.96); Geant > RZ/File 21 mygeom.geom on Zebra RZ mygeom.geom g2root mygeom.geom mygeom.C ROOT Geometry Package

16. Example : gexam1 //-----------List of Volumes-------------- TGeoVolume *ECAL ; ECAL = gexam1-> MakeTube("ECAL","mat15",0,5.898013,12.35774); LEAK = gexam1->MakeTube("LEAK","mat15",0,5.898013,0.5617155); LATR = gexam1->MakeTube("LATR","mat15",5.617156,5.813,11.23); BLOC = gexam1->MakeTube("BLOC","mix21",0,5.617156,11.23431); //-----------List of Nodes-------------- gexam1->SetTopVolume(ECAL); ECAL->AddNode(LEAK,1,new TGeoTranslation(0,0,-11.79603)); ECAL->AddNode(LEAK,2,new TGeoTranslation(0,0,11.79603)); ECAL->AddNode(LATR,1,gGeoIdentity); ECAL->AddNode(BLOC,1,gGeoIdentity); TGeoVolume *RTUB = BLOC->Divide("RTUB",1,20,0,0.2808578); TGeoVolume *RING = RTUB->Divide("RING",3,20,-11.31,1.131); gexam1->CloseGeometry(); } void gexam1() { TGeoMaterial *mat; TGeoMixture *mix; TGeoManager *gexam1; gexam1 = new TGeoManager("gexam1","gexam1.C"); //-----------List of Materials and Mixtures-------------- mat = new TGeoMaterial("mat9","ALUMINIUM",26.98,13,2.7); mix = new TGeoMixture("mix10","IRON(COMPOUND)",3); mix->DefineElement(0,55.847,26,0.703964); mix->DefineElement(1,58.71,28,0.9900000E-01); mix->DefineElement(2,51.998,24,0.197); mat = new TGeoMaterial("mat11","COPPER",63.54,29,8.96); mat = new TGeoMaterial("mat13","LEAD",207.19,82,11.35); mat = new TGeoMaterial("mat14","URANIUM",238.03,92,18.95); mat = new TGeoMaterial("mat15","AIR",14.61,7.3,0.1205E-02); mat = new TGeoMaterial("mat16","VACUUM",0,0,0); mix = new TGeoMixture("mix21","BGO(COMPOUND)",3); mix->DefineElement(0,208.98,83,0.6710563); mix->DefineElement(1,72.59,32,0.1748205); mix->DefineElement(2,15.999,8,0.1541233); mix = new TGeoMixture("mix22","LEAD GLASS",6); mix->DefineElement(0,207.19,82,0.65994); mix->DefineElement(1,39.102,19,0.7990000E-02); mix->DefineElement(2,28.088,14,0.126676); mix->DefineElement(3,22.99,11,0.4007300E-02); mix->DefineElement(4,15.999,8,0.199281); mix->DefineElement(5,74.922,33,0.2004850E-02); gexam1.C code generated automatically by g2root ROOT Geometry Package

17. Brahms 2649 nodes ROOT Geometry Package

18. CMS 1.3 million nodes ROOT Geometry Package

19. Atlas 29 million nodes ROOT Geometry Package

20. Atlas ROOT Geometry Package

21. Atlas ROOT Geometry Package

22. Alice ROOT Geometry Package

23. Alice 3 million nodes ROOT Geometry Package

24. TGeo performance vs Geant3 Number gtmedi Root Geant3/ gtmedi Root Geant3/ nodes physics physics Root random random Root Gexam1 425 3.08 1.84 1.67 6.60 4.39 1.50 Gexam3 86 2.87 2.15 1.33 3.47 2.50 1.38 Gexam4 12781 2.51 2.20 1.14 12.09 11.18 1.08 Brahms 2649 5.82 3.04 1.91 4.17 1.93 2.16 Tesla 15370 6.56 5.58 1.17 12.95 7.15 1.81 CDF 24422 14.81 4.31 3.43 20.94 5.85 3.57 Minos_near 30988 30.93 20.99 1.47 21.57 13.70 1.57 BTeVEcal 52 1.57 1.08 1.45 1.78 0.73 2.43 BTeV 295310 45.27 25.88 1.75 197.06 26.83 7.34 CMSEcal 251713 5.60 1.81 3.09 5.69 1.74 3.27 CMS 1166310 33.57 8.76 3.83 39.09 24.98 1.56 LHCb 1533488 7.98 6.75 1.18 12.58 2.89 4.35 Alice 3080198 11.50 8.63 1.33 11.45 7.28 1.57 Atlas 29046966 8.90 9.94 0.89 32.48 23.39 1.38 ROOT Geometry Package

25. BteV ROOT Geometry Package

26. Validation Procedure Use one million points generated by Geant3. Compare G3 path vs TGeo found path (pictures for a CDF event) ROOT Geometry Package

27. Validation Procedure • Using points generated by Geant3 applications • grecord.f --> mygeom.geom, mygeom.hbook • Play-back these points in Geant3 using only the Geant3 geometry package. Compute g3path, snext, safety in myresults.hbook • h2root myresults.hbook myresults.root • Same operation with TGeo classes. Compare g3path with tgeopath, same for snext, safety • Some discrepancies with Geant3 (see next) ROOT Geometry Package

28. Validation ProcedureDifferences Geant3 TGeo • Due to precision problems in Geant3, points recorded at the volume boundaries may be found on the other side by TGeo. • When volumes declared MANY in Geant3 overlap and have sub-volumes also MANY, Geant3 is not always reporting the right answer. In general it does not matter, sometimes it does. • In this exercise, we also found original errors in the detector description, eg wrong parameters. ROOT Geometry Package

29. Status of the implementation - test of gtnext • Visualization - best tool for checking the algorithms • The "width" of the boundaries due to floating point limitations was determined for some shapes • This diffusion effect is crucial for fixing stepping actions in order to trigger expected inside/ouside response of the modeler • The diffusion was defined as the distance between extrapolated point from step and closest point that changes this in/out response. ROOT Geometry Package

30. Status of the implementation • Geant3 geometries - almost fully mapped (still not supporting multiple positioning for volumes having shapes with negative parameters which then are divided - quite seldom topology) • "Where am I ?" - fully implemented • Tested on a dozen of geometries, including all 4 LHC experiments • Performance w.r.t GEANT3 - OK. The average gain factor ~1.5-2.0 , increasing for flat-like geometries • Consistency vs. GEANT3 response reasonable : still few % differences, but fully understood • Still scope for increasing speed, specially for cylindrical symmetries, where the current voxelization algorithm is not efficient enough. ROOT Geometry Package

31. Status of the implementation - gtnext • "Which is the next crossed boundary ?" - about 80% implemented, still a couple of weeks to work on it. • Algorithms per shape improved w.r.t G3 for some shapes • New functionalities added : normals to surfaces at crossing points, accurate distance to closest node, direction vector to closest point • Features for stepping added : flags for entering and exiting ROOT Geometry Package

32. Summary • The new Geometry Package looks very promising. • We have been able to model all existing large detectors. • Performance is better than Geant3. • We are planing to interface it via TVirtualMC to Geant3, Geant4 and Fluka. • Alpha release with ROOT version 3.03/07 ROOT Geometry Package