Pions from in-beam Kaon Decay

Pions from in-beam Kaon Decay


This case is handled via pichdecays.F. This file is a container for charged pion decays.
The routine pichdecay_manager is called in kaon decay generators where one ore more charged pions are present in the final state (e.g. kch2pipi0.F).
Two pion decay types are implemented in pich2lnu.F and pich2lnug.F, with the possibility to choose the lepton type (electron or muon).

Software implementation


  • scripts/env.sh
  • GNUmakefile

New generator files:

  • Generator/pichdecays.F
  • Generator/pich2lnu.F
  • Generator/pich2lnug.F
Generator to be modified:
  • Generator/kch2pipi0.cc (not working yet)

Macro file to be modified:

  • macros/StandardRun.mac

C++ files to be modified:

  • src/CMC.cc, include/CMC.hh
  • src/DatacardManager.cc, include/DatacardManager.hh
  • src/DatacardMessenger.cc, include/DatacardMessenger.hh
  • src/PrimaryGeneratorAction.cc, include/PrimaryGeneratorAction.hh
  • src/G4CMCDecayer.cc, include/G4CMCDecayer.hh
  • src/PrimaryGeneratorMessenger.cc

How to run

To run this channel:

  • specify the charged pion decay type in the StandardRun.mac file, at the line with the tag /decay/pichDecay.
    Available charged pion decay types:
    • 0: pi is passed to Geant4;
    • 1: pi --> e nu;
    • 2: pi --> mu nu;
    • 3: pi --> e nu g;
    • 4: pi --> mu nu g;

Run the software giving the modified macro file as input parameter, e.g. on an SL6 machine:

cd /afs/phas.gla.ac.uk/data/na62/software01/NA62MC
source scripts/env.sh
NA62MC macros/StandardRun.mac

In the StandardRun.mac file, one has to pay attention to the following instructions:

/decay/pichDecay 2 
as explained above. Then use

/output/fileName pluto.root
to set where the output goes.

Verbosity can be set with

/run/verbose 1
/event/verbose 1
/tracking/verbose 1

Temporary patch (removed in r > 736)

  • The generation of the K+ -> pi+pi0, pi+ -> mu+ nu, pi+0 -> gg process is handled by Fortran code independent from the NA62MC software. This produces a kdecayggl.txt file containing informations on three final state particles: mu+, gamma, gamma.

  • In src/PrimaryGeneratorAction.cc a new case has been added, in which the kdecayggl.txt file is read and the three input particles are inserted into the NA62 apparatus.
    In the macros/StandardRun.mac file this option can be selected with /beam/SetBeam PionDecayTest.
    The handling of the new parameter has been implemented in src/PrimaryGeneratorMessenger.cc.

How to check the output

An event analyzer is provided inside the NA62Analysis framework.

In /afs/phas.gla.ac.uk/data/na62/software01/UserAnalysis the "MCTruthAnalyzer" can be used to debug the MC events produced with NA62MC.

  • The code is in Analyzers/src/MCTruthAnalyzer.cc

After sourcing scripts/env.sh from within UserAnalysis/

  • Compile with NA62AnalysisBuilder.py configFiles/MCTruthAnalyzer.conf
  • Run with ./MCTruthAnalyzer -i ../NA62MC/pluto.root -o test.root -v kUser --config configFiles/MCTruthAnalyzer.run
    The kUser verbose flag has to be used to get on screen information on generated particles.


This will be documented in technical note CERN-

Topic revision: r10 - 2015-11-20 - DanProtopopescu
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