mc - Geant4 example

This is an example of Geant4 simulation and data processing for physics experiment.

Features

• Prepared physics, materials, primary generators
• Output as ROOT TTree
• Human friendly logger
• Data pocessing examples
• Track git hash
• Basic tests

Usage

Requirement

• Geant4 11.0
• ROOT 6 with C++17 option
• Qt (for interactive mode)

You can run easily, without installing ROOT and Geant4 using virtual machine. When you use this virtual machine, you have to do source $ROOTSYS/bin/thisroot.sh before running.

Install & build

First of all, clone this repository,

> git clone https://github.com/mzks/mc
> cd mc

Then, execute ./make.sh or step-by-step build.

> cmake -B build
> cmake --build build
> cmake --install build --prefix .

The ./make.sh script will execute build, install, and full test automatically.

Run MC

• GUI interactive mode

> ./bin/mc -i

• Batch mode

> ./bin/mc -m run.mac

Command line options are

-h --help               	shows help message and exits [default: false]
-v --version            	prints version information and exits [default: false]
-m --macro              	set macro filename for batch mode [default: "run.mac"]
-o --output             	output file name with .root [default: "mc.root"]
-i --interactive        	run as interactive mode, not batch [default: false]
-s --seed               	run as interactive mode, not batch [default: 0]
-p --path-to-macro      	set macro search path with colon-separated list [default: ".:bench:../bench"]
-a --ascii              	Output with ascii file, not root [default: false]
-k --keep-history       	Make a file to keep command list [default: false]
-r --root-include-macro 	Store command list to root file [default: false]

With -k option, the used macro list will be generated as like mc_macro.txt. This is a macro which can be used as a input, thus you can run again with the file with ./bin/mc -m mc_macro.txt.

The bench/run.mac is an example of the input macro for the mc. As a primary particle generator, three options are provided with /mcgun/selectGunAction The first option (pg) is a mcParticleGun. This is a G4ParticleGun with some user customed command. If you want to custom your primary particle, it is a good option when you generates 1 particle per each event. The second option is a G4GeneralParticleSource (gps). The third option is fully-user customed primary particle generator (custom). The primary particle is defined at mcPrimaryGeneratorAction.

Output file format

The generated file with mc includes parameters and a TTree named mc.

Included parameters are

Parameter name	Example	Description
git_sha1	46f7d136b2e52ff0dc52ba25f871ea753730a03d-dirty	The source git SHA1 hash in build phase. If the source is modified, the hash has a suffix, -dirty
git_date	Mon Aug 22 18:14:29 2022	The source git date
git_subject	Add tests for reconstruction	The source git subject
G4Version	Geant4 version Name: geant4-11-00-patch-02 [MT],(25-May-2022)	Used Geant4 version
ROOTVersion	6.26/04	Used ROOT version
physicslist_name	FTFP_BERT_HP	Base physicslist name
seed	1 (TParameter<int>)	Simulation seed
gaps_custom_physics	True (TParameter<bool>)	Enable user (GAPS) custom physics
commands	/control/execute run.mac /control/verbose 1 etc.	Applied UI command list in used Geant4 macro

and the TTree branches are

Branch name	Type	Description
nHit	UInt_t	Number of particles detected with any "SensitiveDetector", should be match with the other std::vector::size().
x	vector<double>	X of touched position [mm].
y	vector<double>	Y of touched position [mm].
z	vector<double>	Z of touched position [mm].
time	vector<double>	Time that particles touch the "SensitiveDetector" [ns]
eIn	vector<double>	Energy incoming particles into "SensitiveDetector" [MeV]
eDep	vector<double>	Energy deposition in "SensitiveDetector" [MeV]
TrackID	vector<int>	Track ID of Geant4 (Initial particle starts at 1).
copyNo	vector<int>	Copy No (user tag for physical volume in Geant4)
particle	vector<int>	Incoming particle ID with PDG code.

Run processing

> ./bin/mcProcessing -i mc.root -o processed.root
> ./bin/response -i mc.root -o response.root

The processing (with legacy TTree reader) and response (with RDataFrame) scripts are just skeltons. The meaningful branches should be implemented.