void extractTree(const char *file, int event_num) {
TFile *f = new TFile(file);
TTree *tree = (TTree*) f->Get("T");
RAT::DS::Root *rds = new RAT::DS::Root();
tree->SetBranchAddress("ds", &rds);
tree->GetEntry(event_num);
RAT::DS::MC *mc = rds->GetMC();
int nTracks = mc->GetMCTrackCount();
Particle *trackmap = new Particle[nTracks+1];
for (int j = 0; j < nTracks; j++) {
RAT::DS::MCTrack *track = mc->GetMCTrack(j);
int tid = track->GetID();
int pid = track->GetParentID();
Particle *cur = &trackmap[tid];
trackmap[pid].addChild(cur);
RAT::DS::MCTrackStep *first = track->GetMCTrackStep(0);
RAT::DS::MCTrackStep *last = track->GetLastMCTrackStep();
int nSteps = track->GetMCTrackStepCount();
TVector3 *steps = new TVector3[nSteps];
for (int k = 0; k < nSteps; k++) {
steps[k] = track->GetMCTrackStep(k)->GetEndpoint();
}
cur->setProperties(track->GetParticleName(),first->GetProcess(),last->GetProcess(),steps,nSteps);
}
trackmap[1].dumpList(cout);
}