THStack histogram

Newbie
1

hi, im trying to stack these 5 samples,
i wonder why, the value of events is different when i add more sample to stack
here is a plot of 2, signal (15 & 55GeV)and 3 signal,(15,35,55GeV)
on the 3 signal plot, there is also an access of 55Gev sample on top of 35Gev sample,
what may be the cause?
Screenshot 2020-12-09 at 1.36.14 PM Screenshot 2020-12-09 at 1.36.36 PM

/ root file
  TFile *f_sig15 = new TFile("/Users/applestudio/Desktop/rootFILES/4LAnalyzer_h125_4mu_zd15.root");
 TFile *f_sig35 = new TFile("/Users/applestudio/Desktop/rootFILES/4LAnalyzer_h125_4mu_zd35.root");
  TFile *f_sig55 = new TFile("/Users/applestudio/Desktop/rootFILES/4LAnalyzer_h125_4mu_zd55.root");
  TFile *f_bkg_zz4lep = new TFile("/Users/applestudio/Desktop/rootFILES/4LAnalyzer_Background_zz4lep.root");
  TFile *f_bkg_pph4l = new TFile("/Users/applestudio/Desktop/rootFILES/4LAnalyzer_Background_pph4l.root");
    
 // get branch in tree
  TH1F *h_sig15 = (TH1F*)f_sig15->Get("mZb_4mu")->Clone("h_sig15");
  TH1F *h_sig35 = (TH1F*)f_sig35->Get("mZb_4mu")->Clone("h_sig35");
  TH1F *h_sig55 = (TH1F*)f_sig55->Get("mZb_4mu")->Clone("h_sig55");
  TH1F *h_bkg_zz4lep = (TH1F*)f_bkg_zz4lep->Get("mZb_4mu")->Clone("h_bkg_zz4lep");
  TH1F *h_bkg_pph4l = (TH1F*)f_bkg_pph4l->Get("mZb_4mu")->Clone("h_bkg_pph4l");
    
    
    float lumi = 250000;
    
    double nevents = 25000;
    double xs = 48.58; //normalize to SM Higgs Crossection
   // double ZZ4lep_BRXS = 1.256; //pb according to AN-16-442
    double BR_SMHiggs = 1.25e-4;
    
  
 // normalize using scale to SM Higgs crossection & BR (total events 25k)
  
  
  TCanvas *c = new TCanvas("c","c");
  h_sig15->Scale(xs*(0.00004166667)*lumi/nevents);// signal = 1/3BR
  h_sig35->Scale(xs*(0.00004166667)*lumi/nevents);
  h_sig55->Scale(xs*(0.00004166667)*lumi/nevents);
  h_bkg_zz4lep->Scale(xs*BR_SMHiggs*lumi/nevents);
  h_bkg_pph4l->Scale(xs*BR_SMHiggs*lumi/nevents);
     
  //stack normalized samples
  h_sig15->SetFillColor(kMagenta-10);
  h_sig35->SetFillColor(kCyan-10);
  h_sig55->SetFillColor(kYellow);
  h_bkg_zz4lep->SetFillColor(kSpring-9);
  h_bkg_pph4l->SetFillColor(kRed+2);
    
  THStack *hs = new THStack("hs", "zd mass");
  hs->Add(h_bkg_zz4lep);
  hs->Add(h_bkg_pph4l);
  hs->Add(h_sig15);
  hs->Add(h_sig35);
  hs->Add(h_sig55);
  hs->Draw("HIST");
  hs->GetXaxis()->SetTitle("mass of zd (4mu channel)");
  hs->GetYaxis()->SetTitle("Number of Events");
  hs->GetXaxis()->SetRangeUser(12,80);
  
//  printf("LocalMaximum: %f\n",h->GetMaximum());

  TLegend *leg = new TLegend(0.9,0.7,0.7,0.9);
  //(plg hujung x dekat 0,lebar dekat xaxis dr 0,lebar dekat yaxis dr 0,atasbawah on y axis)
  // dia count dr 0-1
  leg->SetHeader("Sample");
  leg->AddEntry("h_sig15","mZd = 15GeV","f");
  leg->AddEntry("h_sig35","mZd = 35GeV","f");
  leg->AddEntry("h_sig55","mZd = 55GeV","f");
  leg->AddEntry("h_bkg_zz4lep","zz4l","f");
  leg->AddEntry("h_bkg_pph4l","pph4l","f");
  leg->Draw();
    

  c->SaveAs("cubanormalize.eps");

Thank you
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ROOT Version: 6.22
Platform: mac catalina 10.15.7
Compiler: Not Provided

2

Maybe you want this?

hs->Draw("HIST,nostack");
3

thnks