A GEANT4 Simulation of the A GEANT4 Simulation of the CrystalBall@MAMICrystalBall@MAMI

Derek GlazierDerek GlazierUniversity of EdinburghUniversity of Edinburgh

GEANT4 OverviewGeant4 is the successor of GEANT3, the world-standard toolkit for HEP detector simulation

Geant4 is an object-oriented C++ toolkitthe goal is to provide all that is needed to build a wide variety of physics simulation applications

code is open, modular – available for all to download

In particular a variety of geometries and physics models can be “plugged in”

Additionally a number of independent visualisation tools can be used

Extensive documentation and tutorials provided

Principal references:NIM A506, 250 (2003) and IEEE Trans. Nucl. Sci. 53, 270 (2006)

Geant4 is the successor of GEANT3, the world-standard toolkit for HEP detector simulationGeant4 is an object-oriented C++ toolkit

the goal is to provide all that is needed to build a wide variety of physics simulation applications

code is open, modular – available for all to download

In particular a variety of geometries and physics models can be “plugged in”

Additionally a number of independent visualisation tools can be used

Extensive documentation and tutorials provided

Principal references:NIM A506, 250 (2003) and IEEE Trans. Nucl. Sci. 53, 270 (2006)

http://geant4.web.cern.ch/geant4/

User PackagesDefine material and geometry

G4VUserDetectorConstruction

Select appropriate particles and processes and define production threshold(s)

G4VUserPhysicsList

Define the way of primary particle generationG4VUserPrimaryGeneratorAction

Define the way to extract useful information from Geant4G4UserSteppingAction, G4UserTrackingAction, etc.G4VUserDetectorConstruction,G4UserEventActionG4SensitiveDetector, G4VHit, G4VHitsCollection

Defines information passed to AcquRoot via A2CBOutput

Import mkin, AcquMC files

Controls detector and target geometries

Electromagnetic Physics“standard” package (1 keV and up)

multiple scattering, ionization, bremsstrahlungCompton, pair production, photo-electric, annihilationsynchrotron, Cerenkov, transition radiation, high energy muon

Also _EMV version =G4.7.1 EM physics ~20% faster

“low energy” packageuses database information to extend interactions below 1 keVmany of the same processes as offered in “standard”

Possible to track optical photons (from Cerenkov, Scintillation)reflection/refraction, absorption, Rayleigh, wavelength shifting

Requires production cuts (minimum distance a particle can travel to be tracked) Default 1mm

We use

Hadronic PhysicsLow Energy and High Energy Parametrized (LEP, HEP) models for all hadrons

LEP and HEP models are the re-engineered versions of the GHEISHAmodels (parametrized from data)

fast energy is conserved on average, not event-by-event

Bertini-style cascade for low energies (< 10 GeV) classical cascade model, uses free-space cross sections

Pros and cons: designed for use in HEP trackers, collider detectors good for neutrino beams, kaon interactions

Gamma-nuclear model added for E < 3.5 GeV

Binary cascade for low energies (< 3 GeV) detailed theory-driven model upper limit due to dependence on resonances

LEP, HEP for hyperons, anti-baryons, LE kaons Gamma-nuclear model added for E < 3.5 GeV:l

~Standard G3

Recomended G4

CrystalBall GeometryImport from GEANT3 complicated by GEANT4

handling of overlapping volumes

Could not use major/minor triangle constructionEach crystal placed individually

Additional materials (skirting, equator) takenfrom cbsim with someupdates from UCLA

Cut crystals in tunnel region realised through Boolean solidsi.e CCUT cylinder from G3 is rotated and subtracted from each cut crystal

Geometry with RayTracer

TAPS Geometry

Originally Implemented as in cbsim

Additional interactivity added to go between MAMI-B and MAMI-C

Boxes, vetos copied from cbsimDummy crystals only for MAMI-BVetos read out independent of BaF2

PbWO4 crystals have been IntroducedCan be read out into combinedBaF2-PbWO4 AcquRoot classBaF2_PWO_09.dat

MWPC Geometry

MAMI-B MWPC implemented as for cbsim(Jamie Robinson)Just materials no individual stripsCan use Sven's ReadDecoded (smears initial4 vectors for tracks)

Updated for MAMI-C (David Howdle)Supports etc from PauloIndividual wires included (not effect CPU much)Position readout for each strip cylinder

New AcquRoot ReadDecoded (A2/acquroot/TA2CylMWPC.*)Smears strip position :Phi by wire spacing, Z by Then calculates position in each chamberand track as for real data

Should be included in new MWPC classes

PID and TargetsPID1 and PID2 implemeted

Different mountings required for each

Accurate lightguide geometrys

Right angular wedge shaped scintillators(cbsim uses trapezoid)

Standard solid and cryo targets are as for cbsim

New solid target for 2008 C beamtimes (J. Robinson)

Variable cell size allowed for cryo target(M. Firminger)

Users should check their own solid target geometryDo not trust standard implementation!!!

Sim. will check to be sure given vertex is inside celland choose a new one if not!

Polarised TargetLongitudinal target created by Monica Firminger, Sackville

Full geometry including coils and butanol cell Approximate magnetic field consisting 1Tesla in target volume, zero outRequires field map

Gives noticable deflection of 100 MeV pions

coils

cell

Primary Generator Action

mkin AcquMC

h2root

A2PrimaryGeneratorAction

(Use MCNtuple.h for G3 to PDG particle ID

Includes nuclei)

G4 InteractiveParticleGun

particlephasespace

Particle overlapping

A2CBOutput G4 Tracking

/gun/particle pi+/gun/energy 1 MeV/gun/direction ...

Ntuple orTMCPartice

Original 4 vectors

Number of different options for input events

AcquMC, (PLUTO?) and mkin ntuple .root files as for cbsim

Particle phasespace and overlap new for A2PrimaryGeneratorAction

Interactive G4 particle gun useful for testing

Run macro

Running A2 Simulation : DetectorSetup.mac

####Use the crystal ball?/A2/det/useCB 1#####Use TAPS?/A2/det/useTAPS 0####Configure TAPS/A2/det/setTAPSFile taps07.dat/A2/det/setTAPSZ 145 cm/A2/det/setTAPSN 384/A2/det/setTAPSPbWO4Rings 2####Use the PID/A2/det/usePID 2/A2/det/setPIDZ 0. cm/A2/det/useMWPC 2/A2/det/useTOF 0/A2/det/setTOFFile TOF.par##Set the target#/A2/det/useTarget Cryo###Cryo targets : G4_lH2, A2_lD2####/A2/det/targetMaterial G4_lH2/A2/det/setTargetLength 4.8 cm#/A2/det/useTarget Solid/A2/det/useTarget Polarized/A2/det/targetMaterial A2_HeButanol

WARNING

Please check defaultDetectorSetup.macbefore running.Make sure it is the configuration you want

Running A2 Simulation : Run ConfigurationMacro File doppi0.mac

#####Pre-Initialisation#Choose a physics list, for a full listing type #/A2/physics/ListPhysics/A2/physics/Physics QGSP_BIC####Initialise/run/initialize##the initial random number seed/A2/generator/Seed 1111111#Set the number of particles to be tracked from the input ntuple/A2/generator/NToBeTracked 3#give the indexes of the particles to be tracked#(have a look at the branch names in the input file)/A2/generator/Track 2/A2/generator/Track 3/A2/generator/Track 4#Open the file and set up the ntuple for reading/A2/generator/InputFile /scratch/dglazier/kin_pi0p_100000.root#####Output#Open the output file for writing/A2/event/setOutputFile /scratch/dglazier/testQGSP_BIC.root

Also possible to give input filename as command lineArgument, output is then the same appended with tr_

Equator material

G3

G4Coherent pi0 analysis, noticed detection efficiencyDiffered by ~5% between G3/G4

Large deviation in ϕ~0 regionRealised G3 had much larger Fe thickness at equatorNote, G3 version used Marc/Sven's mod.

With same thickness G3/G4 agree to about 1%

UCLA prefer thin version

Suggestion, make cross sections with 10o gap in ϕ acceptance at equatorIf the right thickness is used the cross sections should not change

Recoil polarimetry (Sikora)

Φ (π-proton) versus Φπ-structure consistent with Top hemisphere offset ~3mm

Is it possible to use the wirechambers to measure the CB positions?

G4 Binary Cascade model does excellent job of reproducing proton nucleus interactions, Cross sections and angular distributions

Scattered proton angular distribution

Hadronic interactionsK+ cross sections

Nice agreement with previous measurements of K+Σ cross sectionSensitive to K+ nucleus interaction, as cannot tag K+ if inelastic interaction

July 07April 08JLAB

Bug fixes/Updates● For next release..

● Inner can material set to iron (M. Sikora) (sent round already)

● Vertex position restriction (makes sure event comes from target material) – only worked first event! (D. Werthmueller)

● Allow adjustment of hemisphere seperation

● S. Prakhov's updated geometry

● Some significant changes to iron geometries and cut crystals

● Other suggestions...

Open IssuesContributions welcome/needed

● Detectors :

● Cerenkov (Class exists, requires details/volunteer)

● Targets :

● Polarised

– Needs transverse geometry (E.Downie)– Field map (A.Mushkarenkov)

● 3He cryo and polarised??

● AcquRoot .Offline,.dat , ReadDecoded normalised with standard user classes (see A2/acquroot directory)

● What additions do experiments need???

The Past See presentation R. Brune

● http://indico.cern.ch/conferenceDisplay.py?confId=116419

The first version of GEANT appeared in 1974. It was a very simple framework for simulation between NA3, NA4 and Omega experiments. (about 5000 LOC)

GEANT2 came in 1977 with more functions to control the initialisation, stepping phases (10000 LOC).

GEANT3 came in 1981 in OPAL, then many experiments. It was a huge step. A powerful geometry system, electromagnetic physics based on EGS3/4 and interfaces with hadronic shower packages like Tatina, Gheisha and Fluka. (150000 LOC)

The PresentGEANT4 came in 1995 following the directions taken by GEANT3 but written in C++. The geometry system was along the same lines as in GEANT3 and the electromagnetic physics was a continuation (with the same authors) of what was in GEANT3.

GEANT4 had a long list of developments and improvements in the physics sector, in particular hadronic physics and this work is going on.

Recent reports from LHC have demonstrated the high quality of the simulations with GEANT4 physics.

The FutureGEANT5 = GEANT4 + ROOT + ... = Next year

Motivation

Primarily from LHC

These tools should evolve in a more compatible framework

Should incorporate FastMCs (G4 too slow for many analysis)

From ROOT want to use I/O, Interpreters, Graphics (event display), Math, Infrastructure, parallelisation, Geometry TGeo

i.e. Will look like ROOT will transport like GEANT4

(by default, but other transporters (fast/statistical) will possible)

The Future for the CB?

Benefits

Highly flexible tool (lots of configuration options)Easier to installParallel processing (including multicore or GPU)Will be further physics developments

Predictive modellingInterface to HEP event generators...

Keep pace with computational developments

Realistic

GEANT4 already quite flexible, probably not used (in this collaboration)Flexibility ~ more complicated to run, users just want a start button!Physics developments may have limited impact at MAMI energiesGEANT4 physics will continue to be developed seperatelyMigration would be ~ 2 years away