void A1()
{
	
	TFile *input = new TFile("AuAu200GeV_SM_NT3_DecaysOff_0_20fm_file0.root", "read");
	
	TTree *tree = (TTree*)input->Get("tr");
	
	Int_t Event, Mult, cent;
	
	Int_t Stat[12000]; //Stat = 0 means Spectators Stat>0 means participants
	Int_t PID[12000]; //Particle ID	
	Float_t Mass[12000]; //Mass
	Float_t E[12000]; //Energy
	Float_t y[12000]; //Rapidity
	Float_t Pt[12000]; //Transverse Momentum 
	Float_t P[120000]; // |P| mod P
	Float_t eta[12000]; //Pseudo-rapidity
	Float_t phi[12000]; //Azimuthal angle
	Float_t b; //Impact parameter
	
	
	Float_t Imp[12000]; //Impact parameter array
	Float_t phi_part[12000]; //Azimuthal angle of participating nucleons
	
	Float_t r_2[12000]; // r^2 = Nx^2 +Ny^2 +Nz^2 It is for each multiplicity. Index runs over j. r_2[j]
	Float_t r_2_sum[12000]; // r_2[0] + r_2[1] + .... + r_2[Mult].	It is for each collision. Index runs over i. r_2_sum[i]
	Float_t r_2_avg[12000]; // <r^2> .	It is for each collision. Index runs over i. r_2_avg[i]
	
	
	
	Float_t eccen_cos[12000]; // cos term for each participant 
	Float_t eccen_sin[12000]; // sin term for each participant
	
	Float_t eccen_cos_sum[12000]; // sum of cos terms for each participant 
	Float_t eccen_sin_sum[12000]; // sum of sin terms for each participant 
	
	Float_t eccen_cos_sum_avg[12000]; //eccen_cos_sum divided by # of participapting nucleons for that particular collision
	Float_t eccen_sin_sum_avg[12000]; //eccen_sin_sum divided by # of participapting nucleons for that particular collision
	
	Float_t eccen_num[12000]; // Numerator of eccentricity expression
	Float_t eccen[12000]; //Eccentricity 
	
	
	Float_t Nx[12000];
	Float_t Ny[12000];
	Float_t Nz[12000];
	
	
	Float_t Px[12000];
	Float_t Py[12000];
	Float_t Pz[12000];
	
	tree->SetBranchAddress("Event", &Event);
	tree->SetBranchAddress("Mult", &Mult);
	tree->SetBranchAddress("Imp", &b);
	
	tree->SetBranchAddress("PID",PID);
	tree->SetBranchAddress("Mass",Mass);
	
	tree->SetBranchAddress("Nx",Nx);
	tree->SetBranchAddress("Ny",Ny);
	tree->SetBranchAddress("Nz",Nz);
	
	
	tree->SetBranchAddress("Px",Px);
	tree->SetBranchAddress("Py",Py);
	tree->SetBranchAddress("Pz",Pz);
	
	Int_t entries = tree->GetEntries();
	

	/* Rapidity (y), Pseudorapidity (eta), Transverse momentum (Pt), Azimuthal angle (phi) */ 
		
		
	for(Int_t i = 0; i<entries; i++)
	{	
		tree->GetEntry(i);
		for(Int_t j = 0; j<Mult; j++)
		{	
			E[j] = TMath::Sqrt((TMath::Power(Px[j],2)) + (TMath::Power(Py[j],2)) + (TMath::Power(Pz[j],2)) + (TMath::Power(Mass[j],2)));	// Energy
			y[j] = 0.5 * TMath::Log((E[j] + Pz[j]) / (E[j] - Pz[j]));	// Rapidity
			Pt[j] = TMath::Sqrt(TMath::Power(Px[j],2) + TMath::Power(Py[j],2));	// Transverse Momentum
			P[j] = TMath::Sqrt(TMath::Power(Px[j],2) + TMath::Power(Py[j],2) + TMath::Power(Pz[j],2));	// |P| Magnitude of Momentum
			eta[j] = 0.5 * TMath::Log((P[j] + Pz[j]) / (P[j] - Pz[j]));	// Pseudo-rapidity
			phi[j] = TMath::ATan2(Py[j],Px[j]);	// Azimuthal angle
		}
			 
	}		
	
		
	/*ECCENTRICITY*/
	
	
	/*TCanvas *c9 = new TCanvas();
	TProfile *hprof1 = new TProfile("hprof1", "Eccentricity vs b for n = 2 for S = 0", 40, 0, 20);
	
		
	Int_t N[12000];	// For counting the number of participants

	 
	Int_t n = 2;
	
	for(Int_t i = 0; i<entries; i++)
		{	
			tree->GetEntry(i);
			N[i] = 0;
			r_2_sum[i] = 0;
			eccen_cos_sum[i] = 0;
			eccen_sin_sum[i] = 0;
			for(Int_t j = 0; j<Mult; j++){
						
				if(Stat[j] > 0){
				
					phi_part[j] = TMath::ATan2(Py[j],Px[j]);
					r_2[j] = (TMath::Power(Nx[j],2)) + (TMath::Power(Ny[j],2));
					r_2_sum[i] = r_2_sum[i] + r_2[j];
					N[i]+=1; //counts the number of participating nucleons for each collision
				
					eccen_cos[j]= r_2[j] * TMath::Cos(n * phi_part[j]);
					eccen_sin[j]= r_2[j] * TMath::Sin(n * phi_part[j]);
				
					eccen_cos_sum[i] = eccen_cos_sum[i] + eccen_cos[j];
					eccen_sin_sum[i] = eccen_sin_sum[i] + eccen_sin[j];
				}
		}
		
		r_2_avg[i] = r_2_sum[i]/N[i];
		eccen_cos_sum_avg[i] = eccen_cos_sum[i]/N[i];
		eccen_sin_sum_avg[i] = eccen_sin_sum[i]/N[i];
		eccen_num[i] = TMath::Sqrt((TMath::Power(eccen_cos_sum_avg[i],2)) + TMath::Power(eccen_sin_sum_avg[i],2)); //Numerator term for eccentricity 
		eccen[i] = eccen_num[i]/r_2_avg[i];
		//cout << eccen[i] << endl;
		Imp[i] = b;
		hprof1->Fill(Imp[i],eccen[i]);
	}
	
	c9->cd();
	hprof1->GetXaxis()->SetTitle("Impact Parameter b (in fm)");
	hprof1->GetYaxis()->SetTitle("Eccentricity for n = 2 for S = 0");
	hprof1->Draw();
	c9->BuildLegend();*/
	
	//TFile* f1 = new TFile("2_S0.root", "CREATE");
	//hprof1->Write();
	
	TH1F *myhist = new TH1F();
	TLeaf *leaf = tree->GetLeaf("Mult");
	for (Int_t i=0; i<entries; i++){
		leaf->GetBranch()->GetEntry(i);	
		myhist->Fill(leaf->GetValue());
	}
	myhist->Draw();

	
	//input->Close();
}