#include "TCanvas.h"
#include "TH1F.h"
#include "TF1.h"
#include "TTree.h"
#include "TLegend.h"
#include "TChain.h"
#include "TLatex.h"
#include "TStyle.h"
using namespace std;
void Read1()
 {
   TFile *f = new TFile("TEST.root");
   TTree *t3 = (TTree*)f->Get("hit_Phi_vec"); 
   Float_t delta_eta, delta_phi, delta_R, eta_hit, phi_hit, track_eta, track_phi, hitper_event, pt1;
   cout<<"the branch is going to set"<<endl;
   t3->SetBranchAddress("hit_eta_vec", &eta_hit);
   
   TH1F *hit_eta = new TH1F("hit_eta","",60,2.3,4.3);
   Int_t nentries2= (Int_t)t3->GetEntries();
   
   for (Int_t j=0;j<nentries2;j++)
    {
     t3->GetEntry(j); 
     hit_eta->Fill(eta_hit);
    }
   
   TCanvas *c3 = new TCanvas("c3","corelation",600,700);
   c3->cd();
   hit_eta->GetYaxis()->SetTitle("Fraction of the events");
   hit_eta->SetLineWidth(3);
   Double_t scale2 = 1/(hit_eta->Integral(0,hit_eta->GetNbinsX()+1));
   hit_eta->Scale(scale2);
   hit_eta->Draw("HIST");
   hit_eta->GetYaxis()->SetRangeUser(0, 0.06);
   TLatex latex2;
   latex2.DrawLatex(4,-0.005,"hit_#eta");
 }