void tree2w() {
// write tree2 example
//create a Tree file tree2.root
TFile f("tree2.root","recreate");
//create the file, the Tree
TTree t2("t2","a Tree with data from a fake Geant3");
// declare a variable of the C structure type
Gctrak_t gstep;
// add the branches for a subset of gstep
t2.Branch("vect",gstep.vect,"vect[7]/F");
t2.Branch("getot",&gstep.getot,"getot/F");const Int_t MAXMEC = 30;
// PARAMETER (MAXMEC=30)
// COMMON/GCTRAK/VECT(7),GETOT,GEKIN,VOUT(7)
// + ,NMEC,LMEC(MAXMEC)
// + ,NAMEC(MAXMEC),NSTEP
// + ,PID,DESTEP,DESTEL,SAFETY,SLENG
// + ,STEP,SNEXT,SFIELD,TOFG,GEKRAT,UPWGHT
typedef struct {
Float_t vect[7];
Float_t getot;
Float_t gekin;
Float_t vout[7];
Int_t nmec;
Int_t lmec[MAXMEC];
Int_t namec[MAXMEC];
Int_t nstep;
Int_t pid;
Float_t destep;
Float_t destel;
Float_t safety;
Float_t sleng;
Float_t step;
Float_t snext;
Float_t sfield;
Float_t tofg;
Float_t gekrat;
Float_t upwght;
} Gctrak_t;
t2.Branch("gekin",&gstep.gekin,"gekin/F");
t2.Branch("nmec",&gstep.nmec,"nmec/I");
t2.Branch("lmec",gstep.lmec,"lmec[nmec]/I");
t2.Branch("destep",&gstep.destep,"destep/F");
t2.Branch("pid",&gstep.pid,"pid/I");
//Initialize particle parameters at first point
Float_t px,py,pz,p,charge=0;
Float_t vout[7];
Float_t mass = 0.137;
Bool_t newParticle = kTRUE;
gstep.step = 0.1;
gstep.destep = 0;
gstep.nmec = 0;
gstep.pid = 0;
//transport particles
for (Int_t i=0; i<10000; i++) {
//generate a new particle if necessary (Geant3 emulation)
if (newParticle) {
px = gRandom->Gaus(0,.02);
py = gRandom->Gaus(0,.02);
pz = gRandom->Gaus(0,.02);
p = TMath::Sqrt(px*px+py*py+pz*pz);
charge = 1;
if (gRandom->Rndm() < 0.5) charge = -1;
gstep.pid += 1;
gstep.vect[0] = 0;
gstep.vect[1] = 0;
gstep.vect[2] = 0;
gstep.vect[3] = px/p;
gstep.vect[4] = py/p;
gstep.vect[5] = pz/p;
gstep.vect[6] = p*charge;
gstep.getot = TMath::Sqrt(p*p + mass*mass);
gstep.gekin = gstep.getot - mass;
newParticle = kFALSE;
}
// fill the Tree with current step parameters
t2.Fill();
//transport particle in magnetic field (Geant3 emulation)
helixStep(gstep.step, gstep.vect, vout);
//make one step
//apply energy loss
gstep.destep = gstep.step*gRandom->Gaus(0.0002,0.00001);
gstep.gekin -= gstep.destep;
gstep.getot = gstep.gekin + mass;
gstep.vect[6]= charge*TMath::Sqrt(gstep.getot*gstep.getot - mass*mass);
gstep.vect[0] = vout[0];
gstep.vect[1] = vout[1];
gstep.vect[2] = vout[2];
gstep.vect[3] = vout[3];
gstep.vect[4] = vout[4];
gstep.vect[5] = vout[5];
gstep.nmec = (Int_t)(5*gRandom->Rndm());
for (Int_t l=0; l<gstep.nmec; l++) gstep.lmec[l] = l;
if (gstep.gekin < 0.001) newParticle = kTRUE;
if (TMath::Abs(gstep.vect[2]) > 30) newParticle = kTRUE;
}
//save the Tree header. The file will be automatically
// closed when going out of the function scope
t2.Write();
}
void tree2aw()
{
//create a Tree file tree2.root
//create the file, the Tree and a few branches with
//a subset of gctrak
TFile f("tree2.root","recreate");
TTree t2("t2","a Tree with data from a fake Geant3");
Gctrak *gstep = new Gctrak;
t2.Branch("track",&gstep,8000,1);
//Initialize particle parameters at first point
Float_t px,py,pz,p,charge=0;
Float_t vout[7];
Float_t mass = 0.137;
Bool_t newParticle = kTRUE;
gstep->lmec = new Int_t[MAXMEC];
gstep->namec = new Int_t[MAXMEC];
gstep->step = 0.1;
gstep->destep = 0;
gstep->nmec = 0;
gstep->pid = 0;
//transport particles
for (Int_t i=0;i<10000;i++) {
//generate a new particle if necessary
if (newParticle) {
px = gRandom->Gaus(0,.02);
py = gRandom->Gaus(0,.02);
pz = gRandom->Gaus(0,.02);
p = TMath::Sqrt(px*px+py*py+pz*pz);
charge = 1; if (gRandom->Rndm() < 0.5) charge = -1;
gstep->pid += 1;
gstep->vect[0] = 0;
gstep->vect[1] = 0;
gstep->vect[2] = 0;
gstep->vect[3] = px/p;
gstep->vect[4] = py/p;
gstep->vect[5] = pz/p;
gstep->vect[6] = p*charge;
gstep->getot = TMath::Sqrt(p*p + mass*mass);
gstep->gekin = gstep->getot - mass;
newParticle = kFALSE;
}
// fill the Tree with current step parameters
t2.Fill();
//transport particle in magnetic field
helixStep(gstep->step, gstep->vect, vout); //make one step
//apply energy loss
gstep->destep = gstep->step*gRandom->Gaus(0.0002,0.00001);
gstep->gekin -= gstep->destep;
gstep->getot = gstep->gekin + mass;
gstep->vect[6] = charge*TMath::Sqrt(gstep->getot*gstep->getot - mass*mass);
gstep->vect[0] = vout[0];
gstep->vect[1] = vout[1];
gstep->vect[2] = vout[2];
gstep->vect[3] = vout[3];
gstep->vect[4] = vout[4];
gstep->vect[5] = vout[5];
gstep->nmec = (Int_t)(5*gRandom->Rndm());
for (Int_t l=0;l<gstep->nmec;l++) {
gstep->lmec[l] = l;
gstep->namec[l] = l+100;
}
if (gstep->gekin < 0.001) newParticle = kTRUE;
if (TMath::Abs(gstep->vect[2]) > 30) newParticle = kTRUE;
}
//save the Tree header. The file will be automatically closed
//when going out of the function scope
t2.Write();
}
