1. 25/03/2003Simulation Application for the LHCb Experiment CHEP2003 25 March 2003 Presented by: W. Pokorski / CERN Authors: I. Belyaev, Ph. Charpentier, S.Easo, P. Mato, J. Palacios, W.Pokorski, F. Ranjard, J. van Tilburg Simulation Application for the LHCb Experiment

2. 25/03/2003Simulation Application for the LHCb Experiment 1 Contents Introduction to LHCb Overview of Gauss project GiGa – Gaudi interface to GEANT4 Physics validation Summary

3. 25/03/2003Simulation Application for the LHCb Experiment 2 Large Sample of Events with B d and B s Mesons Most of the b hadrons are produced at small polar angles LHCb: Single Forward Arm Spectrometer with Open Geometry Measure CKM angles from the CP asymmetries in the final states of B-meson decays LHCb Experiment Precision Measurements of CP violation in the B Meson System

4. 25/03/2003Simulation Application for the LHCb Experiment 3 GAUDI – LHCb software framework all of the LHCb event processing software is built within a framework – Gaudi framework separation between data and algorithms data store-centred architectural style separation between transient and persistent data isolation of user codes/algorithms from underlying persistency technologies components interact through their abstract interfaces

5. 25/03/2003Simulation Application for the LHCb Experiment 4 GAUDI - Object Diagram Converter Algorithm Event Data Service Persistency Service Data Files Algorithm Transient Event Store Detec. Data Service Persistency Service Data Files Transient Detector Store Message Service JobOptions Service Particle Prop. Service Other Services Histogram Service Persistency Service Data Files Transient Histogram Store Application Manager Converter Event Selector Interactive Service

6. 25/03/2003Simulation Application for the LHCb Experiment Gauss application – overall structure Event generation primary event generator (Pythia, Herwig, etc…) specialised decay package (EvtGen,...) pile-up generation Detector simulation geometry (LHCb -> G4) tracking through materials (G4) hit creation (G4) MC truth generation Digitization subdetector specialised algorithms detector response simulation Generation Sequence Simulation Sequence Digitization Sequence HepMC MCevent time

7. 25/03/2003Simulation Application for the LHCb Experiment Gauss application - design Sensitive Detectors G4 Physics Lists LHCb Event Model Digitization Algorithms Detector Data XmlDDDB GiGa HepMC Pythia6.205 EvtGen Magnetic Field Svc 5

8. 25/03/2003Simulation Application for the LHCb Experiment 6 GiGa overview GEANT4 Interface for Gaudi Applications or Gaudi Interface to GEANT4 Applications GEANT4 callable and controllable from within GAUDI environment common detector geometry source used by other applications (reconstruction, visualisation) communication via Transient Stores (Event, Detector Data) as any other service or algorithm in Gaudi use of common services (ParticlePropertySvc, RandomNumberSvc, MagneticFieldSvc, etc.)

9. 25/03/2003Simulation Application for the LHCb Experiment 7 GiGa structure Geant4 Algorithm Event Service Persistency Service Data Files Algorithm Transient Event Store Detec. Service Persistency Service Data Files Transient Detector Store Application Manager GiGa Service G4 Hits G4 Kine GiGaKine Conversion Service Cnv Converter Other Services Action GiGaHits Conversion Service G4 Geom GiGaGeom Conversion Service

10. 25/03/2003Simulation Application for the LHCb Experiment GiGa features it’s a Gaudi service provides access to internal Geant4 event loop via GiGaRunManager all interactions with Geant4 only through abstract interfaces of GiGa Service minimizes the couplings to Geant4 allows loading external physics lists instantiates (using Abstract Factory pattern) different “actions” (makes them to be plugable components) 8

11. 25/03/2003Simulation Application for the LHCb Experiment Sensitive Detectors & Hits G4TrackerHits (Geant4) GiGaSensDetTracker lvVolume (XmlDDDB) GiGaTrackerHitsCnv MCHits (/Event/MC/OT/Hits) Geant4 world Gaudi world ProcessHit() creates invoked when particle passed through the sensitive volume converts to: 9

12. 25/03/2003Simulation Application for the LHCb Experiment 1010 Detector Simulation – “physics lists” physics lists: crucial part of the whole simulation program most of the stuff already implemented in Geant4 some specific processes needed implementation for RICH: photoelectric process (creation of photoelectrons in HPDs), energy loss in the silicon of HPDs GiGa modular physics lists allows dynamic loading (via jobOptions) of particular physics “sublists” expected to increase flexibility and to make validation easier

13. 25/03/2003Simulation Application for the LHCb Experiment Physics validation comparison to the test-beam data validation of Rayleigh scattering, Cherenkov radiation, photoelectric effect, energy loss in the Silicon for RICH detectors studies of different hadronic physics models in hadronic calorimeter simulations comparison to the Geant 3 simulation occupancies, momentum distributions, time of flight, energy deposition distributions, etc 11

14. 25/03/2003Simulation Application for the LHCb Experiment Vertex Locator physics validation (1/2) Geant3 Geant4 Number of hits per event Energy deposition in the silicon (eV) Geant3 Geant4 12

15. 25/03/2003Simulation Application for the LHCb Experiment Vertex Locator physics validation (2/2) Geant3 Geant4 Geant3 Geant4 Time of Flight (ns) Particle energy (GeV) 13

16. 25/03/2003Simulation Application for the LHCb Experiment Outer Tracker physics validation (1/2) Geant3 Geant4 XY distribution Number of hits per event 14

17. 25/03/2003Simulation Application for the LHCb Experiment Outer Tracker physics validation (2/2) Time Of Flight (ns) Momentum distribution (GeV) Geant3 Geant4 15

18. 25/03/2003Simulation Application for the LHCb Experiment 1616 Summary Current Status: we can run GEANT4 simulation with all the subdetectors included (complete LHCb detector geometry), realistic Pythia events and Geant4 proposed physics list we are testing/validating subdetector specific code and physics processes Planning: large test productions starting from the summer definite move from the old Geant3 simulation to the new Geant4 based one, early next year