// $\eta\omega$: 8.6\times 10^{-4}
// $\eta\rho$:  5.6 \times 10^{-3}
// (f_{0}(600), f_{0}(980)):  5.6 \times 10^{-3}
// (f_{0}(1500)): 1.96 \times 10^{-3}

   
Double_t myfunction(Double_t *x, Double_t *par)
   {
     double L = par[4]*1e-24;
     double sg_sig = par[2]*1e-9;
     double br = par[3];
     //    double br = 0.02*0.015*0.2274;//omega-eta
     //     double br = 0.02*0.2274;//rho-eta
     double sg_bk = 50*1e-3;//*1e-27;
     
     // Double_t t = x[0]*(604800.);//week
     Double_t t = x[0]*(604800.*4);//months
     //   Double_t t = x[0]*(604800.*4.*12.);//years
     // Double_t t = x[0]*(60.*60.*24);//day
     Double_t eSig =par[0];
     Double_t eBkg =par[1];
     double sig_contr = sg_sig*br*eSig;
     double bkg_contr = sg_bk*eBkg;
     //   cout<<"TMath::Sqrt(L*t) = "<<TMath::Sqrt(L*t)<<" sig_contr = "<<sig_contr<<" bkg_contr = "<<bkg_contr<<endl;
     Double_t f = TMath::Sqrt(L*t)*(sig_contr)/(TMath::Sqrt(sig_contr+bkg_contr));
      return f;
   }

void FoM(double eff_sig=0.40,double eff_bkg=5e-6){
//void FoM(double eff_sig=0.70,double eff_bkg=1e-7){
  double Lumi=1e31;
  double sig_sg = 10.;
  //  double br_sig=0.02;
  //  double br_sig=0.004;
    double br_sig=0.005;
  double time = 1e4/(eff_sig*Lumi*1e-24*sig_sg*1e-9*br_sig*60.*60.*24);
  // double time = 4317./(eff_sig*Lumi*1e-24*sig_sg*1e-9*br_sig*60.*60.*24);
  cout<<"Time for 1e4 events if sigma(sig)="<<sig_sg<<" nb is "<<time<<" days"<<endl;
  // double Nbkg =  50*1e-3*Lumi*1e-24*time*eff_bkg/(60.*60.*24.);
  // cout<<" "<<Nbkg<<" will be reconstructed!"<<endl;
  TF1 *f1 = new TF1("myfunc",myfunction,0,100,5);
  f1->SetParameters(eff_sig,eff_bkg, sig_sg,br_sig,Lumi);
  f1->SetParNames("eff_sig","eff_bkg","sig_cs","sig_br","L");
  f1->GetXaxis()->SetTitle("Time, weeks");
  f1->GetYaxis()->SetTitle("Significance, #sigma");
  //  f1->Draw();
  sig_sg = 50.;
  time = 1e4/(eff_sig*Lumi*sig_sg*br_sig*1e-33*60.*60.*24.);
  cout<<"Time for 1e4 events if sigma(sig)="<<sig_sg<<" nb is "<<time<<" days"<<endl;
  // Nbkg =  50*1e-3*Lumi*1e-24*time*eff_bkg/(60.*60.*24.);
  // cout<<" "<<Nbkg<<" will be reconstructed!"<<endl;
  TF1 *f3 = new TF1("myfunc",myfunction,0,100,5);
  f3->SetParameters(eff_sig,eff_bkg, sig_sg,br_sig,Lumi);
  f3->SetParNames("eff_sig","eff_bkg","sig_cs","sig_br","L");
  f3->SetLineColor(8);

  sig_sg = 100.;
  double time = 1e4/(eff_sig*Lumi*br_sig*sig_sg*1e-33*60.*60.*24.);
  cout<<"Time for 1e4 events if sigma(sig)="<<sig_sg<<" nb is "<<time<<" days"<<endl;
  // Nbkg =  50*1e-3*Lumi*1e-24*time*eff_bkg/(60.*60.*24.);
  // cout<<" "<<Nbkg<<" will be reconstructed!"<<endl;
  TF1 *f2 = new TF1("myfunc",myfunction,0,100,5);
  f2->SetParameters(eff_sig,eff_bkg, sig_sg,br_sig,Lumi);
  f2->SetParNames("eff_sig","eff_bkg","sig_cs","sig_br","L");
  f2->SetLineColor(4);
  f2->GetXaxis()->SetTitle("Time, months");
  f2->GetYaxis()->SetTitle("Significance");
  f2->Draw();
  f3->Draw("same");
  f1->Draw("same");
TLegend *legsh = new TLegend(0.7,0.75,0.98,0.97);
 legsh->SetFillColor(0);
 legsh->AddEntry(f1,"#sigma_{s} = 10 nb","l");
 legsh->AddEntry(f3,"#sigma_{s} = 50 nb","l");
 legsh->AddEntry(f2,"#sigma_{s} = 100 nb","l");
 legsh->Draw();

}