void d0pi_d0_bkg(const char *filename="skimmed_proc11_prompt_leto_afterBCS_ta_myflag_md0pi.root", const char *outfilename= "all_bkg.root")  
{
  // Read your input file
  TFile *f = new TFile(filename,"READ");
  TTree *tree = (TTree*) f->Get("DstD0PiKK");
  
  Double_t Dz_M, Dst_M, Dst_isSignalAcceptMissingGamma, DzPi_M;
  Int_t my_flag;

  tree->SetBranchAddress("Dz_M",&Dz_M);
  tree->SetBranchAddress("Dst_M",&Dst_M);
  tree->SetBranchAddress("DzPi_M",&DzPi_M);
  tree->SetBranchAddress("Dst_isSignalAcceptMissingGamma",&Dst_isSignalAcceptMissingGamma);  
  tree->SetBranchAddress("my_flag",&my_flag);
    
  TFile *f1 = new TFile(outfilename,"RECREATE");
  TTree *t1 = new TTree("d0pi_d0_distributions","tTREE");//creating a tree 
  Double_t d0pi_kk, d0pi_kpipi0, d0pi_e, d0pi_kpi, d0pi_mu, d0_kk, d0_kpipi0, d0_e, d0_kpi, d0_mu;

  //d0pi_kk=DzPi_M;
  TBranch *b_d0pi_kk=t1->Branch("d0pi_kk",&d0pi_kk,"d0pi_kk/D");
  TBranch *b_d0pi_kpipi0=t1->Branch("d0pi_kpipi0",&d0pi_kpipi0,"d0pi_kpipi0/D");
  TBranch *b_d0pi_e=t1->Branch("d0pi_e",&d0pi_e,"d0pi_e/D");
  TBranch *b_d0pi_kpi=t1->Branch("d0pi_kpi",&d0pi_kpi,"d0pi_kpi/D");
  TBranch *b_d0pi_mu=t1->Branch("d0pi_mu",&d0pi_mu,"d0pi_mu/D");

  TBranch *b_d0_kk=t1->Branch("d0_kk",&d0_kk,"d0_kk/D");
  TBranch *b_d0_kpipi0=t1->Branch("d0_kpipi0",&d0_kpipi0,"d0_kpipi0/D");
  TBranch *b_d0_e=t1->Branch("d0_e",&d0_e,"d0_e/D");
  TBranch *b_d0_kpi=t1->Branch("d0_kpi",&d0_kpi,"d0_kpi/D");
  TBranch *b_d0_mu=t1->Branch("d0_mu",&d0_mu,"d0_mu/D");
  
  // Loop over candidates
  Long64_t nentries = tree->GetEntriesFast();
  for (Long64_t i=0; i<nentries; i++){
    tree->GetEntry(i);
    //kk
    if(Dz_M>1.855&&Dz_M<1.875){
      
      if(my_flag==1||my_flag==33||my_flag==325||my_flag==410||my_flag==1117||my_flag==1387){
	d0pi_kk=DzPi_M;
	b_d0pi_kk->Fill();
      }
      //kpipi0    
      if(my_flag==4||my_flag==7||my_flag==8||my_flag==16||my_flag==20||my_flag==49||my_flag==207||my_flag==218||my_flag==225||my_flag==503){
	d0pi_kpipi0=DzPi_M;
	b_d0pi_kpipi0->Fill();	
      }
      
      //electronic
      if(my_flag==838||my_flag==251||my_flag==172||my_flag==156||my_flag==155||my_flag==24||my_flag==113||my_flag==63||my_flag==310||my_flag==45||my_flag==21||my_flag==3){
	d0pi_e==DzPi_M;
	b_d0pi_e->Fill();
    }
      //kpi
      if(my_flag==352||my_flag==57||my_flag==41||my_flag==11||my_flag==2){
	d0_kpi=DzPi_M;
	b_d0pi_kpi->Fill();
      }
      //muonic
      if(my_flag==1220||my_flag==213||my_flag==144||my_flag==131||my_flag==417||my_flag==122||my_flag==121||my_flag==48||my_flag==18){
	d0pi_mu==DzPi_M;
	b_d0pi_mu->Fill();
      }       
    }
    ///////////////////////
  
     
    if(DzPi_M>2.009&&DzPi_M<2.011){
      
      if(my_flag==1||my_flag==33||my_flag==325||my_flag==410||my_flag==1117||my_flag==1387){
	d0_kk=Dz_M;
	b_d0_kk->Fill();
      }
      //kpipi0    
      if(my_flag==4||my_flag==7||my_flag==8||my_flag==16||my_flag==20||my_flag==49||my_flag==207||my_flag==218||my_flag==225||my_flag==503){
	d0_kpipi0=Dz_M;
	b_d0_kpipi0->Fill();	
      }
      
      //electronic
      if(my_flag==838||my_flag==251||my_flag==172||my_flag==156||my_flag==155||my_flag==24||my_flag==113||my_flag==63||my_flag==310||my_flag==45||my_flag==21||my_flag==3){
	d0_e==Dz_M;
	b_d0_e->Fill();
    }
      //kpi
      if(my_flag==352||my_flag==57||my_flag==41||my_flag==11||my_flag==2){
	d0_kpi=Dz_M;
	b_d0_kpi->Fill();
      }
      //muonic
      if(my_flag==1220||my_flag==213||my_flag==144||my_flag==131||my_flag==417||my_flag==122||my_flag==121||my_flag==48||my_flag==18){
	d0_mu==Dz_M;
	b_d0_mu->Fill();
      }       
      
    }
    //t1->Fill();      		 
  }

 
  t1->Write();
  //t2->Write("", TObject::kOverwrite);

  f1->Close();
  
}