void plot_tracks(){
  float x[50],xtrack[50],y[50],ytrack[50],z[50];
  ifstream track_file;
  track_file.open("junk3");
  for (int i=0;i<50;i++){
    track_file >> x[i];
    track_file >> y[i];
    track_file >> z[i];
  }
  
  TH2F *hr13 = new TH2F("hr13","Track segments",
                        20,200,410,20,-25.,25);
  gStyle->SetOptStat(0);
  hr13->SetXTitle("z (cm)");
  hr13->SetYTitle("x (cm)");
  hr13->Draw();
  

  float pos[3]={-8.040955,-7.481406,213.000000};
  float dir[3]={-0.056444,-0.031782,0.000000};

  TGraph *g0=new TGraph(50,z,x);
   
  g0->SetMarkerStyle(kOpenCircle);
  g0->SetMarkerColor(2);
  g0->SetLineColor(2);
  g0->Draw("P");

  double par[5]={-8.040955,-7.481406,213.000000,-0.056444,-0.03178};
  TF1 *f1= new TF1("f1","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f1->SetParameters(par);
  f1->Draw("same");

  par[0]=5.191975;
  par[3]=0.083540;
  par[4]=0.079144;
  TF1 *f2= new TF1("f2","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f2->SetParameters(par);
  f2->Draw("same");

  par[0]=-10.861805;
  par[2]=273.000000;
  par[3]=-0.077154;
  par[4]=-0.064426;
  TF1 *f3= new TF1("f3","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f3->SetParameters(par);
  f3->Draw("same"); 

  par[0]=8.232714;
  par[3]=0.056718;
  par[4]=0.011401;
  TF1 *f4= new TF1("f4","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f4->SetParameters(par);
  f4->Draw("same");						    

  par[0]=11.444582;
  par[2]=332.000000;
  par[3]=0.057622;
  par[4]=0.014649;
  TF1 *f5= new TF1("f5","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f5->SetParameters(par);
  f5->Draw("same");

  par[0]=-13.651492;
  par[3]=-0.044052;
  par[4]=-0.038575;
  TF1 *f6= new TF1("f6","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f6->SetParameters(par);
  f6->Draw("same");
  
  par[0]=14.853036;
  par[2]=392.000000;
  par[3]=0.031415;
  par[4]=0.004696;
  TF1 *f7= new TF1("f7","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f7->SetParameters(par);
  f7->Draw("same"); 

  par[0]=-16.345502;
  par[3]=-0.039857;
  par[4]=-0.037325;
  TF1 *f8= new TF1("f8","[0]+[3]*(x-[2])/sqrt(1-[3]*[3]-[4]*[4])",par[2]-2,
		   par[2]+12);
  f8->SetParameters(par);
  f8->Draw("same");
}