g4numi¶
The g4numi code consists of code to build a representation of the NuMI beamline geometry and interface it with the Geant4 physics tools. The same geometry is also used for the Flugg simulation. A simple model of incoming proton beam is used as a source of initial particles. The primary output of the this code is an ntuple representing the decays of secondaries that give rise to neutrinos.
building procedure¶
physics processes¶
There is a FNAL Geant4 Effort to improve the physics list used to control (mostly hadronic) interactions in order to better agree with data (e.g. NA49, NA61, etc) in physics regimes that are relevant for the NuMI beam.
Important note about entry values¶
The following are additions to the base g4numi ntuple (nudata). Unlike the rest of the ntuple which uses cm (for lengths) and GeV (for energies and momenta) this portion uses mm and MeV, so take care.
These hold information about the ancestor between the original proton and the neutrino. The arrays are a fixed length of 10 entries, though it is possible for the actual history chain to be longer than that (in which case it is truncated). For any one entry only the indices 0 to min(ntrajectory-1,9) are meaningful. Elements ntrajectory and beyond are filled with junk left over from previous entries; do not use them.
Int_t ntrajectory;
Bool_t overflow;
Int_t pdg[10];
Int_t trackId[10];
Int_t parentId[10];
Double_t startx[10];
Double_t starty[10];
Double_t startz[10];
Double_t stopx[10];
Double_t stopy[10];
Double_t stopz[10];
Double_t startpx[10];
Double_t startpy[10];
Double_t startpz[10];
Double_t stoppx[10];
Double_t stoppy[10];
Double_t stoppz[10];
Double_t pprodpx[10];
Double_t pprodpy[10];
Double_t pprodpz[10];
TString proc[10];
TString ivol[10];
TString fvol[10];