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25/03/2003 Simulation 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
25/03/2003 Simulation Application for the LHCb Experiment 1
Contents
Introduction to LHCb
Overview of Gauss project
GiGa – Gaudi interface to GEANT4
Physics validation
Summary
25/03/2003 Simulation Application for the LHCb Experiment 2
Large Sample of Events with Bd and Bs 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
25/03/2003 Simulation 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 dataisolation of user codes/algorithms from underlying persistency technologies
components interact through their abstract interfaces
25/03/2003 Simulation Application for the LHCb Experiment 4
GAUDI - Object Diagram
Converter
Algorithm
Event DataService
PersistencyService
DataFiles
AlgorithmAlgorithm
Transient Event Store
Detec. DataService
PersistencyService
DataFiles
Transient Detector
Store
MessageService
JobOptionsService
Particle Prop.Service
OtherServices
HistogramService
PersistencyService
DataFiles
TransientHistogram
Store
ApplicationManager
ConverterConverterEventSelector
InteractiveService
25/03/2003 Simulation Application for the LHCb Experiment
Gauss application – overall structure
Event generationprimary event generator (Pythia, Herwig, etc…)
specialised decay package (EvtGen,...)
pile-up generation
Detector simulationgeometry (LHCb -> G4)
tracking through materials (G4)
hit creation (G4)
MC truth generation
Digitizationsubdetector specialised algorithms
detector response simulation
Generation Sequence
Simulation Sequence
Digitization Sequence
HepMC
MCeventtime
25/03/2003 Simulation Application for the LHCb Experiment
Gauss application - design
Sensitive Detectors
G4
Physics Lists
LHCb Event Model
DigitizationAlgorithms
DetectorData
XmlDDDB
GiGa
HepMC
Pythia6.205
EvtGen
MagneticFieldSvc
5
25/03/2003 Simulation 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 Gaudiuse of common services (ParticlePropertySvc, RandomNumberSvc, MagneticFieldSvc, etc.)
25/03/2003 Simulation Application for the LHCb Experiment 7
GiGa structure
Geant4
Algorithm
EventService
PersistencyService
DataFiles
AlgorithmAlgorithm
Transient Event Store
Detec. Service
PersistencyService
DataFiles
Transient Detector
Store
ApplicationManager
GiGaService
G4 Hits
G4 KineGiGaKine
ConversionService
CnvCnvConverter
OtherServices
ActionAction
GiGaHits Conversion
Service
G4 GeomGiGaGeomConversion
Service
25/03/2003 Simulation 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
25/03/2003 Simulation Application for the LHCb Experiment
Sensitive Detectors & Hits
G4TrackerHits
(Geant4)
GiGaSensDetTracker
lvVolume
(XmlDDDB)
GiGaTrackerHitsCnv
MCHits
(/Event/MC/OT/Hits)
Geant4 world
Gaudi world
ProcessHit()
<logvol name="lvU_ActiveLayer" … sensdet="GiGaSensDetTracker/myDet">
creates
invoked when particle passed through the sensitive volume
converts to:
9
25/03/2003 Simulation Application for the LHCb Experiment 10
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 listsallows dynamic loading (via jobOptions) of particular physics “sublists”
expected to increase flexibility and to make validation easier
25/03/2003 Simulation Application for the LHCb Experiment
Physics validation
comparison to the test-beam datavalidation 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 simulationoccupancies, momentum distributions, time of flight, energy deposition distributions, etc
11
25/03/2003 Simulation Application for the LHCb Experiment
Vertex Locator physics validation (1/2)
Geant3Geant4
Number of hits per event Energy deposition in the silicon (eV)
Geant3
Geant4
12
25/03/2003 Simulation Application for the LHCb Experiment
Vertex Locator physics validation (2/2)
Geant3
Geant4
Geant3
Geant4
Time of Flight (ns) Particle energy (GeV)
13
25/03/2003 Simulation Application for the LHCb Experiment
Outer Tracker physics validation (1/2)
Geant3Geant4
XY distributionNumber of hits per event
14
25/03/2003 Simulation Application for the LHCb Experiment
Outer Tracker physics validation (2/2)
Time Of Flight (ns)Momentum distribution (GeV)
Geant3Geant4
15
25/03/2003 Simulation Application for the LHCb Experiment 16
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