| 1 | $Id: README,v 1.3 2002/07/02 18:35:01 asaim Exp $
|
|---|
| 2 | -------------------------------------------------------------------
|
|---|
| 3 |
|
|---|
| 4 | =========================================================
|
|---|
| 5 | Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
|---|
| 6 | =========================================================
|
|---|
| 7 |
|
|---|
| 8 | ExampleN01
|
|---|
| 9 | ----------
|
|---|
| 10 |
|
|---|
| 11 | ExampleN01 is the simplest example in this novice level examples. It has
|
|---|
| 12 | a tracker tube and a sandwitch calorimeter made of boxes. It shoots a
|
|---|
| 13 | geantino (pseudo-particle which has no "real" physics interaction) per
|
|---|
| 14 | one event. This example demonstrates how the basic GEANT4 framework works.
|
|---|
| 15 |
|
|---|
| 16 | 1. Detector description
|
|---|
| 17 |
|
|---|
| 18 | The detector is defined in ExN01DetectorConstruction.cc. Argon gas,
|
|---|
| 19 | aluminum and lead are defined first, where all of them are single element
|
|---|
| 20 | materials. Though materials are assigned for each volume, they will not
|
|---|
| 21 | affect the trajectory of a geantino.
|
|---|
| 22 |
|
|---|
| 23 | The experimental hall, which is the world volume, is made of argon gas
|
|---|
| 24 | and it is a box. The tracker tube made of argon gas is placed at
|
|---|
| 25 | (-1m,0m,0m) respect to the origin of the world volume. The calorimeter
|
|---|
| 26 | block made of lead and it has 19 layers of aluminum plates inside.
|
|---|
| 27 |
|
|---|
| 28 | 2. Physics processes
|
|---|
| 29 |
|
|---|
| 30 | ExN01PhysicsList.cc defines only a geantino and a transportation
|
|---|
| 31 | process. Though cutoff will not be applied onto geantino, a dummy
|
|---|
| 32 | value must be set.
|
|---|
| 33 |
|
|---|
| 34 | 3. Event generation
|
|---|
| 35 |
|
|---|
| 36 | G4ParticleGun is instanciated in the constructor of
|
|---|
| 37 | ExN01PrimaryGeneratorAction class. At the every event, the public
|
|---|
| 38 | method GeneratePrimaries(G4Event*) is invoked. In this method,
|
|---|
| 39 | G4ParticleGun is accessed to generate a primary particle (geantino).
|
|---|
| 40 | Please note that the direction of the primary particle is set
|
|---|
| 41 | just before shooting, i.e. GeneratePrimaryVertex() method invokation.
|
|---|
| 42 | G4ParticleGun class itself does not have any capability of randomizing
|
|---|
| 43 | the energy nor the momentum of the primary particle. Therefore the user
|
|---|
| 44 | should implement randomizing code in the GeneratePrimaries() method.
|
|---|
| 45 |
|
|---|
| 46 | 4. main()
|
|---|
| 47 |
|
|---|
| 48 | exampleN01.cc has the main() method. In the main() method, three
|
|---|
| 49 | mandatory user classes described above are constructed and set to
|
|---|
| 50 | the G4RunManager object. Then, the "Initialize()" method of G4RunManager
|
|---|
| 51 | is invoked.
|
|---|
| 52 | Some UI commands for setting verbosity are applied via hardly coded
|
|---|
| 53 | "ApplyCommand()" method of G4UImanager class.
|
|---|
| 54 | The "BeamOn()" method triggers the event loop. The argument of this
|
|---|
| 55 | method is the number of event in the run.
|
|---|
| 56 |
|
|---|
| 57 |
|
|---|
