Warning, /geant4/examples/extended/hadronic/Hadr10/README is written in an unsupported language. File is not indexed.
0001 This is an example that aims to test the treatment of decays in Geant4.
0002 In particular, we want to test the decays of the tau lepton, charmed and
0003 bottom hadrons, and the use of pre-assigned decays.
0004
0005 Note that pre-assigned decays are decays that are usually specified by
0006 Monte Carlo event generators. For simplicity, and to avoid dependencies
0007 on external code, in this test we don't use any MC generator, and we
0008 pre-assign decays by hand (using the Geant4 decay table: this is done
0009 in the method SteppingAction::UserSteppingAction). But this does not
0010 change anything regarding the testing of the pre-assignment mechanism
0011 of Geant4.
0012
0013 The set-up is very simple: a cylindrical layer, 2 meter long, whose radii
0014 (inner and outer) and material can be specified via UI commands. By default,
0015 the material is Beryllium, with inner radius of 9 mm and outer radius of
0016 11 mm (i.e. the default thickness is 2 mm). In the rest of the world volume,
0017 is filled with G4_Galactic material (i.e. very low density gas).
0018 There is an uniform and constant magnetic field along the z-axis, whose
0019 value is set via UI command.
0020
0021 The primary particle, tau- by default, is shot along the x-axis, starting
0022 from the center (0, 0, 0).
0023 Its kinetic energy, by default 500 GeV, can be set via UI command.
0024
0025 All secondaries are killed immediately, so only the primary particle
0026 is studied.
0027
0028 The only interesting part of this example is the SteppingAction.
0029 The decay of the primary particle is pre-assigned there.
0030 When the primary particle decays, the properties of the decay -
0031 position, momentum, energy, etc. of the particle at the moment
0032 of the decay - are collected and then used to:
0033 - compute the difference between the "MC-truth" decay radius
0034 (defined as the radius at which the primary would have decayed
0035 if there were no magnetic field and interactions with matter,
0036 i.e. no energy loss and no multiple scattering) and the real
0037 decay radius
0038 - compute the angular deflection (in degrees) between the initial
0039 direction of the primary and its final direction at the moment
0040 it decays
0041 - the energy loss (i.e. the difference between the initial kinetic energy
0042 of the primary and the its kinetic energy at the moment of the decay)
0043 - the energy-momentum violation of the decay (i.e. the difference between
0044 the sum of the 4-momenta of the decay products and the 4-momentum of
0045 primary particle at the moment of its decay).
0046 Some of these information are printed out for each decay, and a summary
0047 statistics is printed out at the end of the application.
0048
0049 Look for the string "***LOOKHERE***" for those parameters/options that
0050 are hardwired in the code (i.e. not available via UI command).
0051
0052 This example uses the physics list factory, therefore you can specify
0053 the reference physics list you want to use via the PHYSLIST
0054 environmental variable (by default, if you don't set it, the FTFP_BERT
0055 physics list is used).
0056
0057 To build this example:
0058
0059 mkdir Build; cd Build
0060 cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo \
0061 -DGeant4_DIR=/path-to-geant4-libraries ../.
0062 make
0063
0064 To run it:
0065
0066 ./Hadr10 hadr10.in
0067
0068 which shoots 500 GeV TeV particles - one run of 10'000 events for each
0069 type of particle - along the x-axis, and print out some information
0070 regarding their decays, as well as some summary information at the end
0071 of each run.
