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                     Geant4 - splitting
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Authors: J. A. Ramos-Mendez*, B. A. Faddegon

Department of Radiation Oncology, University of California San Francisco 
* Corresponding author, email to joserm84@gmail.com 

This example is provided by the Geant4-DNA collaboration.

These processes and models are further described at:
http://geant4-dna.org

Any report or published results obtained using the Geant4-DNA software shall 
cite the following Geant4-DNA collaboration publications:
Phys. Med. 31 (2015) 861-874
Med. Phys. 37 (2010) 4692-4708

If use this example, please cite
J Ramos-Mendez, et. Al. Phys. Med. Biol. 62(15), 5908-5925, (2017) DOI: 10.1088/1361-6560/aa7831

---> 1. A brief description

The splitting example uses variance reduction to improve the computational
efficiency of calculations of ionization cluster size distributions. Ionization 
events are scored in a nanoscaled cylinder. Ionized electrons generated by 
the first generation of secondary electrons are split, i.e. new clone electrons
are generated, labeled and propagated. The label is used to classify those 
new particles as if they were produced by independent histories to avoid 
overlapping of tracks at final analysis. The splitting is performed only
if the ionization event occurred in the cylinder.

Geant4-DNA processes are used. 

The example package contains:
- source files (src, include)
- README
- .in, plot.C and visualization macro files

 ****  2. Set-up.

The geometry is a nanoscaled cylinder centered in the world. The medium is 
water everywhere. The dimensions can be defined with
  /detector/diameter 6 nm
  /detector/length   10 nm

User can define the split number (default is 1, i.e. no split) 
with:

  /vrt/numberOfSplit 10

 ****  3. How to run the example.
In interactive mode, run:
  ./splitting
  Idle> /control/execute vis.mac

In batch mode , run:

  ./splitting run.mac

To get visualization, make sure to uncomment the #/control/execute vis.mac line in the macro.

 ****  4. The physics

This example shows:
- how to use the Geant4-DNA processes,
- how to implement the splitting via G4WrappedProcess 
- how to set the splitting in specific region
- how to propagate new track information to secondary particles

A simple electron capture process is also provided in order to kill electrons
below a chosen energy threshold, set in the Physics list.

Look at the PhyscisList.cc file.

 ****  5. Simulation output 

The output results consists in two histograms in root format

- the energy deposit in the cylindrical target 
- the frequency distribution of ionization cluster size 

NOTE: Every time a value is added to a ROOT histogram, it contributes to the statistics.
For this example, to correct estimate the uncertainties is recommended to split the simulation into
several jobs and to calculate the statistics from them: batch mode. Otherwise, the statistical
uncertainty may be underestimated.

 ****  6. Contacts

If you have any questions or wish to notify of updates and/or modification please contact:
 	
J. Ramos-Mendez at joserm84@gmail.com 

 ****  Acknowledgments :

 Sebastien Incerti (CNRS) for its guidance 


