A Short Course on Geant4 Simulation Toolkit Introduction

1
A Short Course on Geant4 Simulation Toolkit
Introduction

• http//cern.ch/geant4
• The full set of lecture notes of this Geant4
  Course is available at
• http//www.ge.infn.it/geant4/events/pisa_jan2006/g
  eant4course.html

2
The role of simulation

• Simulation plays a fundamental role in various
  domains and phases of an experimental physics
  project
• design of the experimental set-up
• evaluation and definition of the potential
  physics output of the project
• evaluation of potential risks to the project
• assessment of the performance of the experiment
• development, test and optimisation of
  reconstruction and physics analysis software
• contribution to the calculation and validation of
  physics results

• The scope of these lectures (and of Geant4)
  encompasses the simulation of the passage of
  particles through matter
• there are other kinds of simulation components,
  such as physics event generators, electronics
  response generation, etc.
• often the simulation of a complex experiment
  consists of several of these components
  interfaced to one another

3
Detector Simulation - General

• General characteristics of a detector simulation
  system
• You specify the geometry of a particle detector
• Then the software system automatically transports
  the particle you shoot into the detector by
  simulating the particle interactions in matter
  based on the Monte Carlo method
• The heart of the simulation the Monte Carlo
  method
• A method to search for solutions to a
  mathematical problem using a statistical sampling
  with random numbers

4
Basic requirements for a simulation system

• Modeling the experimental set-up
• Tracking particles through matter
• Interaction of particles with matter
• Modeling the detector response
• Run and event control
• Accessory utilities (random number generators,
  PDG particle information etc.)
• Interface to event generators
• Visualisation of the set-up, tracks and hits
• User interface
• Persistency

5
The zoo
DPM EA-MC FLUKA GEM HERMES LAHET MCBEND MCU
MF3D NMTC MONK MORSE RTST-2000 SCALE TRAX VMC
EGS4, EGS5, EGSnrc Geant3, Geant4 MARS MCNP,
MCNPX, A3MCNP, MCNP-DSP, MCNP4B MVP,
MVP-BURN Penelope Peregrine Tripoli-3, Tripoli-3
A, Tripoli-4
...and I probably forgot some more
Many codes not publicly distributed A lot of
business around MC
Monte Carlo codes presented at the MC200
Conference, Lisbon, October 2000
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What is ?
OO Toolkit for the simulation of next generation
HEP detectors
Born from the requirements of large scale HEP
experiments

• Geant3
• Fortran
• CERN product
• inadequate for LHC experiments

...of the current generation too ...not only of
HEP detectors
also
An experiment of distributed software production
and management
An experiment of application of rigorous software
engineering methodologies and Object Oriented
technology to the HEP environment

• RD phase RD44, 1994 - 1998
• 1st release December 1998
• 2 new releases/year since then

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Born from the requirements of large scale HEP
experiments
Storage raw recording rate 0.11
GByte/s accumulating at 12-14 PBytes/year Process
ing 70,000 of todays fastest PCs (6 hours
Intel CPU production today) 1000
person-years 0ffline software effort per
experiment 5000 physicistsaround the world,
around the clock 20 years software life-span
LHC

• Geant3
• Fortran
• CERN product
• inadequate for LHC
• experiments

8
An example of user application
FAO/IAEA International Conference on Area-Wide
Control of Insect Pests Integrating the
Sterile Insect and Related Nuclear and Other
Techniques Vienna, May 9-13, 2005
K. Manai, K. Farah, A.Trabelsi, F. Gharbi and O.
Kadri (Tunisia) Dose Distribution and Dose
Uniformity in Pupae Treated by the Tunisian Gamma
Irradiator Using the GEANT4 Toolkit
9
Geant4 Collaboration

• MoU based
• Distribution, Development and User Support of
  Geant4

• CERN, ESA, KEK, SLAC, TRIUMF, TJNL
• INFN, IN2P3, PPARC
• Barcelona Univ., Budker Inst., Frankfurt Univ.,
  Karolinska Inst., Helsinki Univ., Lebedev Inst.,
  LIP, Northeastern Univ. etc.

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What Can Geant4 Do for You?

• Transports a particle step-by-step by taking into
  account the interactions with materials and
  external electromagnetic fields until the
  particle
• loses its kinetic energy to zero,
• disappears by an interaction,
• comes to the end of the simulation volume
• Provides a way for the user to access the
  transportation process and grab the simulation
  results
• at the beginning and end of transportation,
• at the end of each stepping in transportation,
• at the time when the particle is going into the
  sensitive volume of the detector
• etc.
• These are called User Actions

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What You Have to Do for Geant4?

• Three essential information you have to provide
• Geometrical information of the detector
• Choice of physics processes
• Kinematical information of particles going into
  the detector
• Auxiliary you have to prepare
• Magnetic and electric field
• Actions you want to take when you access the
  particle transportation
• Actions you want to take when a particle goes
  into a sensitive volume of the detector
• etc.

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Tools for Input Preparation

• Geant4 provides standard tools to help you to
  prepare input information
• Multiple choices to describe the detector
  geometry
• Combining basic geometry elements (box, cylinder,
  trapezoid, etc)
• Representation by surface planes
• Representation by boolean operation, etc.
• Standard way to define materials in the detector
• A large collection of examples to define various
  materials
• A set of wide variety of particles
• Standard elementary particles (electron, muon,
  proton,.)
• Unstable particles (resonances, quarks, )
• Ions
• Exotic particles (geantino, charged geantino)

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Choice of Physics Processes

• Geant4 provides a wide variety of physics models
  of particle interactions with matter you can
  select
• Category of physics processes
• Standard electromagnetic processes
• Low energy electromagnetic processes
• Hadronic processes
• How to use physics processes
• A rich samples of Physics List provided with
  example applications
• Recommended Physics List (educated guess) for
  hadronic
• physics

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Minimum Software Knowledge to Use Geant4

• C
• Geant4 is implemented in C, therefore a basic
  knowledge of C is mandatory
• C is a complex language, but you are not
  required to be a C expert to use Geant4
• Object Oriented Technology
• basic concepts
• in-depth knowledge needed only for the
  development of complex applications
• Unix/Linux
• Unix/Linux is a standard working environment for
  Geant4, therefore a minimum knowledge/experience
  is required
• How to use basic Unix command
• How to compile a C code
• Windows
• You can use Visual C
• Though still you need some knowledge of Unix
  (cygwin) for installation

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Tools to Help Your Simulation

• User interface
• Interactive mode with terminal or GUI
• Batch mode
• Visualisation
• Trajectory of a particle and its all secondaries
• Detector geometry
• Debugging
• Controllable verbose outputs from the kernel
  during transportation
• Errors in the geometry definition, etc.
• Data analysis