void calc_phi_t_xsecs(double Eg){
  gStyle->SetOptStat(0);
  double eff[50],deff[50];
  double y[50],dy[50];
  double t[50],dt[50];
  double Nps[42];

  int bin=int((Eg-2.8)/0.2);

  ifstream inps("flux.dat");
  for (int i=0;i<42;i++){
    inps >> Nps[i];
    //Nps[i]=2e11;
  }
  inps.close();

  double Nps_sum=Nps[bin];
  
  ifstream in1("phi_t_yields.dat");
  for (int i=0;i<bin;i++){
    string skipline;
    getline(in1,skipline);
    //   cout << skipline << endl;
    
  }
  double dummy;
  in1 >> dummy;
  cout << dummy << endl;
  for (int i=0;i<50;i++){
    in1 >> y[i];
    in1 >> dy[i];
  }
  in1.close();
  ifstream in2("phi_kk_t_acc.dat"); 
  for (int i=0;i<bin;i++){
    string skipline;
    getline(in2,skipline);
    //   cout << skipline << endl;
    
  }
  in2 >> dummy;
  for (int i=0;i<50;i++){
    in2 >> eff[i];
    in2 >> deff[i];
  }
  in2.close();

  double y_acc[50],dy_acc[50];
  for (int i=0;i<50;i++){
    //cout << eff[i] << endl;
    if (eff[i]>0.){
      double scale=1e6/1.293/Nps_sum/0.492/0.04;
      y_acc[i]=scale*y[i]/eff[i];
      // cout << y[i] << endl;
      dy_acc[i]=y_acc[i]*sqrt(deff[i]*deff[i]/(eff[i]*eff[i])+dy[i]*dy[i]/(y[i]*y[i]));
    }
    t[i]=0.02+0.04*i;
    dt[i]=0.02;
  }

  TCanvas *c2=new TCanvas("c2","c2");
  c2->Draw();
  TH2F *h=new TH2F("h","Differential cross section for #phi",10,0,1.5,10,0,2);
  h->SetXTitle("-t [GeV^{2}]");
  h->SetYTitle("d#sigma/dt [#mub/GeV^{2}]");
  h->Draw();

  TGraphErrors *g1=new TGraphErrors(25,&t[2],&y_acc[2],&dt[2],&dy_acc[2]);
  g1->SetLineColor(2);
  g1->SetMarkerColor(2);
  g1->SetMarkerStyle(20);
  g1->Fit("expo");
  g1->Draw("p");

  double ballamx[5]={1.5,0.68,0.23,0.15,0.04};
  double ballamdx[5]={0.3,0.15,0.11,0.10,0.03};
  double ballamt[5]={0.11,0.3,0.5,0.7,1.2};
  double ballamdt[5]={0.09,0.1,0.1,0.1,0.4};
 
  double ballamx_lo[5]={1.22,0.44,0.17,0.24,0.03};
  double ballamdx_lo[5]={0.22,0.12,0.10,0.10,0.02};
  double ballamt_lo[5]={0.1225,0.3,0.5,0.7,1.2};
  double ballamdt_lo[5]={0.0775,0.1,0.1,0.1,0.4};

  TGraphErrors *g2=NULL;
  if (Eg>5){
    g2=new TGraphErrors(5,ballamt,ballamx,ballamdt,ballamdx);
  }
  else{
    g2=new TGraphErrors(5,ballamt_lo,ballamx_lo,ballamdt_lo,ballamdx_lo);
  }
  g2->SetLineColor(8);
  g2->SetMarkerColor(8);
  g2->SetMarkerStyle(22);
  g2->Draw("p");

  TLegend *legend =new TLegend(0.4,0.5,0.8,0.7);
  char mytitle[80];
  sprintf(mytitle,"our measurement at E#gamma=%3.1f GeV",Eg);
  legend->AddEntry(g1,mytitle,"p");
  legend->AddEntry(g2,"Ballam 1973","p");
  legend->Draw();


}