Physics - MC - CutsΒΆ

The general principles in Geant4 regarding secondary particle production cuts are as follows:

  • Each process has its intrinsic limit(s) to produce secondary particles.

  • All particles produced (and accepted) will be tracked up to zero range.

  • Production cuts are assigned to Regions of the geometry.

A region is a collection of geometry volumes. There is always a default region covering the whole geometry, for which there is a suggested global cut in range for gamma, electron and positron productions. Volumes that require different cuts from the global ones shall be grouped into regions and each region can be assigned its own set of cuts.

In MULASSIS, the user has the option to change the global production cuts. It can be a single cut for gamma, electron and positron productions, or different cuts for each type of the three particles, e.g.

Idle> /phys/cuts/global/default 1 um
Idle> /phys/cuts/global/electron 5 um

The above example sets the global cut to 1 micron, but 5 microns for electrons. The default values for the global cut-off length is 10 microns.

In addition, the user can group the shield layers into different regions and apply different cuts to each region:

 1PreInit> /geometry/layer/delete 0
 2PreInit> /geometry/layer/add 0 Aluminium 2 1 cm
 3PreInit> /geometry/layer/add 1 Silicon 3 1 mm
 4PreInit> /geometry/layer/list
 5
 6-------------------------------------------------------------
 7---> The geometry setup has 2 layers:
 8  Layer No.   1            Aluminium:      1 cm
 9  Layer No.   2              Silicon:      1 mm
10
11-------------------------------------------------------------
12PreInit> /geometry/update
13PreInit>
14PreInit> /phys/scenario em
15The registered physics modules are:
16       G4EmStandard
17       Decay
18Idle>
19Idle> /phys/cuts/global/default 1 um
20Idle> /phys/region/add reg-1
21Idle> /phys/region/addalayer reg-1 2
22Idle> /phys/cuts/region/setcut reg-1 0.5 um
23Idle> /phys/cuts/region/cutperparticle reg-1 e- 0.1 um

In this example, the geometry is made of two layers and a different cut for the silicon layer from the global default is required. To do so a new region named reg-1 is created (line 20), then layer 2 is added to reg-1 (line 21). After this the default cut for reg-1, and different cut for electrons in reg-1 are set (lines 22 and 23, respectively).

Note

The /phys/cut and phys/region commands must be issued after the /phys/scenario command.

Mulassis/ml-v02-00/r342