{
TH1F *hEta = new TH1F("heta","Eta Histogram",100,-6,6);
TKey *key; 
char *str2 = "/TreeK";

char filename[100];
for(Int_t j=1; j<4; j++){
sprintf(filename,"Kinematics_%d.root",j);

TFile *f = new TFile(filename,"read");

TIter next(f.GetListOfKeys()); 

while (key = (Key*)next()) 	{ 
			TString t1 = TString(key->GetName())+TString(str2);
			TTree   *tree  = (TTree*)f->Get(t1);//Tree
			TBranch *branch = tree->GetBranch("Particles");//Branch
			TParticle *particles;
			chain.SetBranchAddress("particles",&Particles);
			
			

			branch->SetAddress(&particles);
			Long64_t nentries = chain->GetEntries();
			cout<<"Entries = "<<nentries<<endl;
			Long64_t nbytes = 0;
			for (Long64_t i=0; i<nentries;i++) {
  							branch->GetEntry(i);
							
							TParticlePDG* pdg=particles->GetPDG();
							if(particles->IsPrimary()){
							Int_t charge = pdg->Charge();
							if(charge !=0) {
						
							cout<<"charge= "<<charge<<endl;	
							
  							cout<<"Eta() = "<<particles->Eta()<<endl;
							hEta->Fill(particles->Eta());	
							                }
											  }
		
										}

						} 
				}

hEta->Draw();
}