25/03/2003Simulation Application for the LHCb Experiment CHEP2003 25 March 2003 Presented by: W. Pokorski / CERN Authors: I. Belyaev, Ph. Charpentier,

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


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


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


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


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


Gauss application - design

Sensitive Detectors

G4

Physics Lists

LHCb Event Model

DigitizationAlgorithms

DetectorData

XmlDDDB

GiGa

HepMC

Pythia6.205

EvtGen

MagneticFieldSvc

5


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.)


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


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


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


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


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


Vertex Locator physics validation (1/2)

Geant3Geant4

Number of hits per event Energy deposition in the silicon (eV)

Geant3

Geant4

12


Vertex Locator physics validation (2/2)

Geant3

Geant4

Geant3

Geant4

Time of Flight (ns) Particle energy (GeV)

13


Outer Tracker physics validation (1/2)

Geant3Geant4

XY distributionNumber of hits per event

14


Outer Tracker physics validation (2/2)

Time Of Flight (ns)Momentum distribution (GeV)

Geant3Geant4

15


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

Documents

25/03/2003Simulation Application for the LHCb Experiment CHEP2003 25 March 2003 Presented by: W. Pokorski / CERN Authors: I. Belyaev, Ph. Charpentier,