void fitting(){
  auto f = new TFile ("histossss.root");
  TH1D *k1 = (TH1D*)f->Get("notrigger");
  
  std::vector<std::string> TriggerCut = {"J20", "J40", "J50", "J75", "J100"};
  int n = TriggerCut.size();
 
  TGraphAsymmErrors *eff[n];
  TH1D *h[n];  
    
  for (unsigned i = 0; i < n; i++) {
   f->GetObject(TString::Format("%s", TriggerCut[i].c_str()) , h[i]);  
 
   eff[i] = new TGraphAsymmErrors();
   eff[i]->Divide(h[i], k1);
   eff[i]->SetNameTitle("eff", "Trigger Efficiency"); 
         
   if (i == 0) eff[i]->SetLineColor(kRed-7);
   else if (i == 1) eff[i]->SetLineColor(kBlue+3);
   else if (i == 2) eff[i]->SetLineColor(kViolet+7);
   else if (i == 3) eff[i]->SetLineColor(kAzure+7);
   else eff[i]->SetLineColor(kGreen+1);
   if (i==0) eff[i]->Draw("ap"); 
   else eff[i]->Draw("p same");
  }
  
  auto histEff = (TH1*) h[0]->Clone();
  histEff->Reset(); 
   for (int j = 0; j < eff[0]->GetN(); ++j) { 
     int bin = histEff->FindBin( eff[0]->GetX()[j] );
     histEff->SetBinContent( bin, eff[0]->GetY()[j] ); 
    }
    
    double x_min = histEff->GetXaxis()->GetBinLowEdge(histEff->FindFirstBinAbove(0));
    double x_max = histEff->GetXaxis()->GetBinUpEdge(histEff->FindFirstBinAbove(1)-1);
    
   auto fit = new TF1("sigm",  "(1/(1+ TMath::Exp(-[0]*(x-[1]))))", x_min, x_max); 
   fit->SetParameters(0.2, 50);
   histEff->Fit("sigm", "R");
}