The Forward Liquid Argon Calorimeter of The Forward Liquid Argon Calorimeter of the ATLAS Detectorthe ATLAS Detector

Geant4 Workshop'03Geant4 Workshop'032-6 September. Triumf, Vancouver2-6 September. Triumf, Vancouver

Patricia Méndez Lorenzo. CERN EP/SFT

1. Introduction and Generalities

2. FCAL at TestBeam

3. Simulation of FCAL with Geant4

4. Results of the Simulation

5. Summary 1

Introduction and Generalities

Physics to be done at the LHC

1. Origin of the mass at the electroweak scale; search of Higgs boson

► H γγ for 90<MH<150 GeV

► H ZZ 4l for 130<MH<M

Z

► WW, ZZ fusion with H ZZ, WW l,νν, 2jets for MH up 1 TeV

► pp WH, ZH, ttbar H, H bbbar (Excluded by LEP) for 80<MH<100 GeV

Calorimetry plays a central role on subdetectors design at LHC

2. Deep study of the top and botton quarks

3. Search of new physics: SUSY, technicolours, extra-dimensions....

2

General ATLAS Calorimeter System

Goal:High precision measurements of energy and position of electrons, photons, jets and missing E

T

Requirements:◘ Rapidity coverage◘ Good electron reconstruction ◘ Excellent energy resolution ◘ Accurate measurement of the shower position

Main Elements:◙ One central cryostat barrel and 2T super-conducting solenoid◙ Two endcaps, in each one: one electromagnetic, two hadronic wheels and one forward calorimeter

Hadronic TileCalorimeters

EM AccordionCalorimeters

Hadronic lAr EndCapCalorimeters

Forward lArCalorimeters

3

The ATLAS Forward lAr Calorimeter (FCAL)

Goal of the FCALFull coverage of the system for a good determination of the missing energy (undetected particles as neutrinos)

Design► 1 Electromagnetic copper/liquid argon module (FCAL1)

► 2 Hadronic modules (FCAL2, FCAL3) with tungsten as absorber

Construction► Several prototypes for FCAL1 constructed and tested successfully at Brookhaven and CERN

► Full depth pre-production prototypes for FCAL1 and FCAL2 (Module 0) designed and built in Arizona and Canada in 1998

Barrel EndCap

EM AccordionCalorimeter

Had EndCapCalorimeter

FCALCalorimeter

4

The FCAL at the TestBeam

FCAL1 and FCAL2 prototypes (Module 0) have been tested at CERN in 1998 during a testbeam program with electrons, pions and muons

♦ Detectors and elements includedin the TestBeam Setup included in the Simulation

♦ Description of FCAL moduleas close as possible to realdetectors

FCAL Module 0 test beam in Geant4

Particles enter the setup from the lower left corner

FCAL1 Module 0

FCAL2 Module 0

Cryostat

5

Simulation of FCAL Module 0 with Geant4

Important parts:

Geometry

CryostatEM Module and Had ModulesTestBeam SetUp

Physics

Physical ProcessesInput Particles: electrons

Visualization and histogramming

Visualization packagesAnaphe and Aida

Simulation based on TestBeam'98 data included as a Geant4 advanced example called lAr_calorimeter

6

Simulation of FCAL Module 0 with Geant4

Detector Geometry PartDetector Geometry Part

int main(int argc, char** argv){............

G4RunManager* runManager = new G4RunManager;FCALTestbeamSetup* detector = new FCALTestbeamSetUp;runManager ->SetUserInitialization(detector);

...............

FCALCryostatVolumes FCALTestbeamSetUpSD

FCALEMModule(including

EMParameters.input)

FCALHadModule(including

HadParameters.input)

FCALEMModuleSD FCALHadModuleSD 7

Simulation of FCAL Module 0 with Geant4

Standard Advanced Examples Design for Standard Advanced Examples Design for Definition of Particles and Physical Processes Definition of Particles and Physical Processes

ClassesClasses

► FCALPhysicsList : Standard Particles and Physical Processes defined

► FCALPrimaryGeneratorAction: Definition of X, Y, Z, cos_X, cos_Y, cos_Z for electrons inside

tracks_20GeV.dat, tracks_40GeV.dat, tracks_80GeV.dat and tracks_200GeV.dat in files of 1000 events each.

particleRun ->SetParticlePosition particleRun ->SetParticleMomentumDirection

Defined following parameter definitions inside those files

Standard advanced examples design for the rest of classes 8

Simulation of FCAL Module 0 with Geant4

VisualizationVisualization

Development with OpenGL

All visualization packages includedin FCALVisManager class

Initialization of the drawing via:

(interactively)idle> /control/execute vis.mac

Front View of the System

9

Simulation of FCAL Module 0 with Geant4

5.0.6. Anaphe Implementation of the Aida 3.0 5.0.6. Anaphe Implementation of the Aida 3.0 HistogramsHistogramsMakeFile as simple as possibleMakeFile as simple as possibleifdef G4ANALYSIS_USECPPFLAGS += 'aida-config --include'LDFLAGS += 'aida-config --lib'

Sourcing some startup scripts at CERNSourcing some startup scripts at CERNsetenv G4ANALYSYS_USE 1

setenv PATH ${PATH}: /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts

source /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts

ln -s /afs/cern.ch/sw/lhcxx/share/LHCXX/latest/scripts/* ~/bin/.(just once after the source)The example has been tested using the gcc-2.95.2 compiler inside CERN RedHat 6.1 and 7.3

10

Results of the Simulation

Histograms and NtuplesHistograms and NtuplesThe example produces 6 histograms and ntuples saved in “fcal.his”

Group of histos and ntuples to show the AIDA mechanismus: (included in last release)

Histo1 and Ntuple1 —— > Number of Tracks out of WorldHisto2 and Ntuple2 —— > Number of Secondary ParticlesHisto3 and Ntuple3 —— > Deposited Energy in FCAL1Histo4 and Ntuple4 —— > Deposited Energy in FCAL2

Group of histos and ntuples to compare with data of 1998 test beam: (to include in next release)

Histo5 and Ntuple5 ——> Reconstructed Energy in FCAL1Histo6 and Ntuple6 ——> Reconstructed Energy in FCAL2

11

Results of the Simulation

Comparison between Geant4 and TestBeam Data'98Comparison between Geant4 and TestBeam Data'98

Characteristics of the simulation:Characteristics of the simulation:

♣ Variable to study: Energy deposited in FCAL1 and FCAL2 in the liquid argon of the tube electrode summed into tiles

♣ TestBeam data: ntuples of 5000 events each for 20, 40, 60 and 80 GeV

♣ Initial Simulation Conditions: 1000 electrons are jetted at beam energies of 20, 40, 60 and 80 GeV

♣ Range cut for secondary particles production: 1 mm

♣ Important effects to take into account: noise and digitization has to be parameterized inside the simulation

12

Results of the Simulation

Definition of the variable inside the Simulation

Etilerec

= cMC

x Etilevis

+ Enoise

(defined by event)

Erec

(per event) = Σ Etilerec

cMC

= Monte Carlo electron calibration constant: 1/CMC

= <Evis

>/<Edep

>

Cuts 0.5mm 1.0mm 2.0mmc

MC [%] 1.42 1.41 1.36

Etilevis

= row electron signal recollected in each tile of the moduleE

dep = Total energy deposited inside the module: E

dep = E

beam – E

loss

Eloss

= Energy losses outside the moduleE

noise = correction factor calculated by gaussian smearing centered at 0 and a

width of 8 GeV

13

Results of the Simulation

14

Statistical Test Statistical Test (Thanks to statistics testing team)

Code design to compare Data with Simulation by a p-value test: Probability that both histos are compatible

Test performed for FCAL1 Reconstructed Energy to 20, 40 and 60 GeV

Results of the Simulation

15

Results of the Simulation

16

Chi2 ≈ 300 n.d.f< 90 p-value quite small

p-value very small due to an understimation of the statistical error from test beam data

Quite important for these tests a good error estimation

Further factors to take into accout:

1. Low energy electrons not considered into simulation

2. Constant smearing factor for all events into simulation

Summary

17

♠ A simulation for the module 0 of the lAr calorimeter for the ATLAS detector has been successfully performed with the Geant4 toolkit

♠ Test beam'98 setup included in the simulation

♠ Results included in a Geant4 advanced example

♣ The statistical test results here presented are preliminary, still to be tested

♣ Only FCAL1 reconstructed energy has been checked in the comparison, further data variables have to be included in the whole analysis

♣ 2003 summer data must be tested in the simulation