geant4

This example is intended to check implementation of the processes of muon interactions: ionization, direct (e+,e-) production, mu+mu- pair production, bremsstrahlung, and mu-nuclear interaction. It allows to compute differential cross sections (as function of the energy transfered to secondaries), total cross sections, and to compare with analytic calculations.

GEOMETRY DEFINITION

It is a single box of homogeneous medium. Two parameters define the geometry :

the material of the box,
the (full) size of the box.

The default geometry (1 m of Iron) is constructed in DetectorConstruction, but the above parameters can be changed interactively via the commands defined in DetectorMessenger.

PHYSICS LIST

The Physics List of the example uses the main physics constructor (builder) called "local", which includes only muon, pion, and proton processes under study. As an alternative standard "emstandard_opt0" and "emstandard_opt4" constructors may be used.

Default energy range for EM processes in this example is from 100eV to 1000PeV.

Optionally "muNucl" builder, MuNuclearBuilder, may be added activating muon-nuclear inelastic interaction.

AN EVENT : THE PRIMARY GENERATOR

The primary kinematic consists of a single particle starting at the edge of the box. The type of the particle and its energy are set in PrimaryGeneratorAction (mu+ 10 TeV), and can be changed via the G4 build-in commands of ParticleGun class (see the macros provided with this example).

PHYSICS

The incident particle is a muon. During the tracking, secondary particles are killed.

The number of interactions are plotted as a function of the energy transfered to the secondaries. The total number of interactions is recorded, and the total cross section computed from this.

At RunAction::EndOfRun(..), the above results are compared with analytical calculations. The functions computing the theoretical cross sections have been provided by the G4 MEPhI group, and implemented in MuCrossSections class.

HISTOGRAMS

The test contains 8 built-in 1D histograms, which are managed by the HistoManager class and its messenger, HistoMessenger.

1 Relative muon transferred energy distribution (log10(eps/Emu kin) for knock-on electrons (ionization)
2 ... direct (e+,e-) pair production by muons
3 ... bremsstrahlung by muons
4 ... nuclear interaction by muons
5 ... ionistion for hadrons
6 ... (e+,e-) pair production by hadrons
7 ... bremsstrahlung by hadrons
8 ... direct mu+,mu- pair production by muons

The histos can be activated individually with the command :

/testem/histo/setHisto id nbBins  valMin valMax

min and max values of log10(eps/Emu kin).

At RunAction::EndOfRunAction() the corresponding histos for analytic calculations are
automatically created and filled (histo 11 to 14, and 18).

One can control the name and the type of the histograms file with the command:

/testem/histo/setFileName  name  (default testem17)

It is possible to choose the format of the histogram file : root (default), xml, csv by changing the default file type in HistoManager.cc.

VISUALIZATION

The Visualization Manager is set in the main(). The initialisation of the drawing is done via the commands /vis/... in the macro vis.mac. To get visualisation:

> /control/execute vis.mac

The detector has a default view which is a longitudinal view of the box.

The tracks are drawn at the end of event, and erased at the end of run.

HOW TO START ?

Execute TestEm17 in 'batch' mode from macro files :

% ./TestEm17   allproc.mac

Execute TestEm17 in 'interactive mode' with visualization :

% ./TestEm17
Idle> control/execute vis.mac
....
Idle> type your commands
....
Idle> exit