REAL FUNCTION zee(XDUMMY)
*********************************************************
*                                                       *
* This file was generated by HUWFUN.                    *
*                                                       *
*********************************************************
*
*     Ntuple Id:      60
*     Ntuple Title:   Z events
*     Creation:       15/11/99 15.51.53
*
*********************************************************
*
      LOGICAL         CHAIN
      CHARACTER*128   CFILE
      INTEGER         IDNEVT,NCHEVT,ICHEVT
      REAL            VIDN1,VIDN2,VIDN3,VIDN(10)
*
      COMMON /PAWIDN/ IDNEVT,VIDN1,VIDN2,VIDN3,VIDN
      COMMON /PAWCHN/ CHAIN, NCHEVT, ICHEVT
      COMMON /PAWCHC/ CFILE
*
*--   Ntuple Variable Declarations
*
      REAL zmass,phi12,et12,y,zmass_c,phi12_c,et12_c,y_c,bmstat(4)
     + ,fid(2),etad(2),phi_e(2),etaevent(2),etapes(2),etapad(2),z_vtx(2)
     + ,z_old(2),z0_trk(2),CESX(2),CESZ(2),DX(2),DZ(2),RLsh2(2)
     + ,cesch2(2),pem3ch2(2),pt(2),E_X(2),E_Y(2),E_Z(2),E_CLUST(2)
     + ,Et0(2),Etz(2),had_em(2),Eoverp(2),Ciso4(2),Eiso4(2),Tiso(2)
     + ,COR_E(2),p_x(2),p_y(2),p_z(2),vtx_occ(2),svxphi(2),svxphi_x2(2)
     + ,dphi_exp(2),pesphifit(2),peschi(2),pes_dphi_mea(2),pes_exp(2)
     + ,pemphifit(2),pemchi(2),pem_dphi_mea(2),pem_exp(2)
      INTEGER irun,ievt,Neles,iaccept,Itrig,Iflag(2),L2cls(2),Ireg(2)
     + ,Ichg(2),N3d(2),Nhit_raw(2),Lhit_raw(2),INtrk1(2),INtrk2(2)
     + ,Nsvx(2),Lhit_fin(2),Nexp(2),Lhitexp(2)
*
      COMMON /PAWCR4/ irun,ievt,Neles,iaccept,Itrig,zmass,phi12,et12,y
     + ,zmass_c,phi12_c,et12_c,y_c,Iflag,bmstat,L2cls,fid,etad,phi_e
     + ,Ireg,etaevent,etapes,etapad,Ichg,z_vtx,z_old,z0_trk,N3d,CESX
     + ,CESZ,DX,DZ,RLsh2,cesch2,pem3ch2,pt,E_X,E_Y,E_Z,E_CLUST,Et0,Etz
     + ,had_em,Eoverp,Ciso4,Eiso4,Tiso,COR_E,p_x,p_y,p_z,vtx_occ
     + ,Nhit_raw,Lhit_raw,INtrk1,INtrk2,Nsvx,Lhit_fin,Nexp,Lhitexp
     + ,svxphi,svxphi_x2,dphi_exp,pesphifit,peschi,pes_dphi_mea,pes_exp
     + ,pemphifit,pemchi,pem_dphi_mea,pem_exp
*
*--   Enter user code here
*
      real Et(2),E_over_P(2),mass_ee
 
************************************************************************
*         USE ONLY THESE VARIABLES
************************************************************************
* i=1,2 (two electrons)
*
* E_X(i), E_Y(i), E_Z(i) : i-th electron momentum
*                          from electromagnetic calorimeter
* pt(i)                  : i-th electron transverse momentum
*                          from tracking device
* E_CLUST(i) = i-th electron Electromagnetic calorimeter energy
* had_em(i)  = i-th electron Hadronic energy / EM eneergy
* Ichg(i)    = i-th electron's electric charge
************************************************************************
* From the above variables, you can calculate
*     Et(i) = sqrt(E_X(i)**2 + E_Y(i)**2)
*     E/p(i) = Et(i) / pt(i)
*     e+e- invariant mass
************************************************************************
 
* calculate invariant mass
      mass_ee = (E_CLUST(1)+E_CLUST(2))**2
     +        - (E_X(1)    +E_X(2)    )**2
     +        - (E_Y(1)    +E_Y(2)    )**2
     +        - (E_Z(1)    +E_Z(2)    )**2
      mass_ee = sqrt(mass_ee)
      call hfill(10001,mass_ee,0.,1.)
 
* cut events when electron candidates have transverse momentum < 10 GeV
      if(pt(1).lt.10.) return
      if(pt(2).lt.10.) return
      call hfill(10002,mass_ee,0.,1.)
 
      do i=1,2
         Et(i) = sqrt(E_X(i)**2 + E_Y(i)**2)
         E_over_P(i) = Et(i) / pt(i)
      end do
      if(Et(1).lt.25.) return
      if(Et(2).lt.25.) return
      call hfill(10003,zmass,0.,1.)
 
      do i=1,2
         call hfill(20001,E_over_P(i),0.,1.)
         call hfill(30001,had_em(i),0.,1.)
      end do
 
* remove events if had/em > 0.05
      if(had_em(1).gt.0.05) return
      if(had_em(2).gt.0.05) return
      call hfill(10004,mass_ee,0.,1.)
 
* require the two electrons are oppositely charged
      if(ichg(1)*ichg(2).gt.0) return
      call hfill(10005,mass_ee,0.,1.)
 
* require 0.5 < E/p < 2
      do i=1,2
         if(E_over_P(i).lt.0.5 .or. E_over_P(i).gt.2.) return
      end do
      call hfill(10006,mass_ee,0.,1.)
 
      END