// from S. Menke

void ntuple()
{
  TTree* hioni = new TTree("hioni","hioni");

  const int NPartMax = 10, NHitMax = 20;

  Int_t Nevt;
  Int_t Npart;
  Int_t Nhit[NPartMax];
  Int_t Pid [NPartMax]; 
  Int_t ChamberNb[NPartMax][NHitMax];
  
  Int_t Edep[NPartMax][NHitMax];

  hioni->Branch("Nevt", &Nevt ,"Nevt/I");
  hioni->Branch("Npart",&Npart,"Npart/I");
  hioni->Branch("Nhit",  Nhit ,"Nhit[Npart]/I");
  hioni->Branch("Edep",  Edep ,"Edep[Npart][20]/I");

  int i,j,k;

  for (i=0;i<10;i++) {
    Nevt = i+1;
    Npart = 4;
    for (j=0;j<4;j++) {
      Nhit[j] = 10;
      for (k=0;k<10;k++) {
        Edep[j][k] = j*20+k;
      }
    }
    hioni->Fill();
  }
}