* $Id$
    
C*********************************************************************  
    
      SUBROUTINE LUBOEI_HIJING(NSAV)   
    
C...Purpose: to modify event so as to approximately take into account   
C...Bose-Einstein effects according to a simple phenomenological    
C...parametrization.    
      IMPLICIT DOUBLE PRECISION(D)  
#include "lujets_hijing.inc"
#include "ludat1_hijing.inc"
      DIMENSION DPS(4),KFBE(9),NBE(0:9),BEI(100)    
      DATA KFBE/211,-211,111,321,-321,130,310,221,331/  
    
C...Boost event to overall CM frame. Calculate CM energy.   
      IF((MSTJ(51).NE.1.AND.MSTJ(51).NE.2).OR.N-NSAV.LE.1) RETURN   
      DO 100 J=1,4  
  100 DPS(J)=0. 
      DO 120 I=1,N  
      IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 120  
      DO 110 J=1,4  
  110 DPS(J)=DPS(J)+P(I,J)  
  120 CONTINUE  
      CALL LUDBRB_HIJING(0,0,0.,0.,-DPS(1)/DPS(4),-DPS(2)/DPS(4),  
     &-DPS(3)/DPS(4))   
      PECM=0.   
      DO 130 I=1,N  
  130 IF(K(I,1).GE.1.AND.K(I,1).LE.10) PECM=PECM+P(I,4) 
    
C...Reserve copy of particles by species at end of record.  
      NBE(0)=N+MSTU(3)  
      DO 160 IBE=1,MIN(9,MSTJ(51))  
      NBE(IBE)=NBE(IBE-1)   
      DO 150 I=NSAV+1,N 
      IF(K(I,2).NE.KFBE(IBE)) GOTO 150  
      IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 150  
      IF(NBE(IBE).GE.MSTU(4)-MSTU(32)-5) THEN   
         CALL LUERRM_HIJING(11
     $        ,'(LUBOEI_HIJING:) no more memory left in LUJETS_HIJING')   
        RETURN  
      ENDIF 
      NBE(IBE)=NBE(IBE)+1   
      K(NBE(IBE),1)=I   
      DO 140 J=1,3  
  140 P(NBE(IBE),J)=0.  
  150 CONTINUE  
  160 CONTINUE  
    
C...Tabulate integral for subsequent momentum shift.    
      DO 210 IBE=1,MIN(9,MSTJ(51))  
      IF(IBE.NE.1.AND.IBE.NE.4.AND.IBE.LE.7) GOTO 180   
      IF(IBE.EQ.1.AND.MAX(NBE(1)-NBE(0),NBE(2)-NBE(1),NBE(3)-NBE(2)).   
     &LE.1) GOTO 180    
      IF(IBE.EQ.4.AND.MAX(NBE(4)-NBE(3),NBE(5)-NBE(4),NBE(6)-NBE(5),    
     &NBE(7)-NBE(6)).LE.1) GOTO 180 
      IF(IBE.GE.8.AND.NBE(IBE)-NBE(IBE-1).LE.1) GOTO 180    
      IF(IBE.EQ.1) PMHQ=2.*ULMASS_HIJING(211)  
      IF(IBE.EQ.4) PMHQ=2.*ULMASS_HIJING(321)  
      IF(IBE.EQ.8) PMHQ=2.*ULMASS_HIJING(221)  
      IF(IBE.EQ.9) PMHQ=2.*ULMASS_HIJING(331)  
      QDEL=0.1*MIN(PMHQ,PARJ(93))   
      IF(MSTJ(51).EQ.1) THEN    
        NBIN=MIN(100,NINT(9.*PARJ(93)/QDEL))    
        BEEX=EXP(0.5*QDEL/PARJ(93)) 
        BERT=EXP(-QDEL/PARJ(93))    
      ELSE  
        NBIN=MIN(100,NINT(3.*PARJ(93)/QDEL))    
      ENDIF 
      DO 170 IBIN=1,NBIN    
      QBIN=QDEL*(IBIN-0.5)  
      BEI(IBIN)=QDEL*(QBIN**2+QDEL**2/12.)/SQRT(QBIN**2+PMHQ**2)    
      IF(MSTJ(51).EQ.1) THEN    
        BEEX=BEEX*BERT  
        BEI(IBIN)=BEI(IBIN)*BEEX    
      ELSE  
        BEI(IBIN)=BEI(IBIN)*EXP(-(QBIN/PARJ(93))**2)    
      ENDIF 
  170 IF(IBIN.GE.2) BEI(IBIN)=BEI(IBIN)+BEI(IBIN-1) 
    
C...Loop through particle pairs and find old relative momentum. 
  180 DO 200 I1M=NBE(IBE-1)+1,NBE(IBE)-1    
      I1=K(I1M,1)   
      DO 200 I2M=I1M+1,NBE(IBE) 
      I2=K(I2M,1)   
      Q2OLD=MAX(0.,(P(I1,4)+P(I2,4))**2-(P(I1,1)+P(I2,1))**2-(P(I1,2)+  
     &P(I2,2))**2-(P(I1,3)+P(I2,3))**2-(P(I1,5)+P(I2,5))**2)    
      QOLD=SQRT(Q2OLD)  
    
C...Calculate new relative momentum.    
      IF(QOLD.LT.0.5*QDEL) THEN 
        QMOV=QOLD/3.    
      ELSEIF(QOLD.LT.(NBIN-0.1)*QDEL) THEN  
        RBIN=QOLD/QDEL  
        IBIN=RBIN   
        RINP=(RBIN**3-IBIN**3)/(3*IBIN*(IBIN+1)+1)  
        QMOV=(BEI(IBIN)+RINP*(BEI(IBIN+1)-BEI(IBIN)))*  
     &  SQRT(Q2OLD+PMHQ**2)/Q2OLD   
      ELSE  
        QMOV=BEI(NBIN)*SQRT(Q2OLD+PMHQ**2)/Q2OLD    
      ENDIF 
      Q2NEW=Q2OLD*(QOLD/(QOLD+3.*PARJ(92)*QMOV))**(2./3.)   
    
C...Calculate and save shift to be performed on three-momenta.  
      HC1=(P(I1,4)+P(I2,4))**2-(Q2OLD-Q2NEW)    
      HC2=(Q2OLD-Q2NEW)*(P(I1,4)-P(I2,4))**2    
      HA=0.5*(1.-SQRT(HC1*Q2NEW/(HC1*Q2OLD-HC2)))   
      DO 190 J=1,3  
      PD=HA*(P(I2,J)-P(I1,J))   
      P(I1M,J)=P(I1M,J)+PD  
  190 P(I2M,J)=P(I2M,J)-PD  
  200 CONTINUE  
  210 CONTINUE  
    
C...Shift momenta and recalculate energies. 
      DO 230 IM=NBE(0)+1,NBE(MIN(9,MSTJ(51)))   
      I=K(IM,1) 
      DO 220 J=1,3  
  220 P(I,J)=P(I,J)+P(IM,J) 
  230 P(I,4)=SQRT(P(I,5)**2+P(I,1)**2+P(I,2)**2+P(I,3)**2)  
    
C...Rescale all momenta for energy conservation.    
      PES=0.    
      PQS=0.    
      DO 240 I=1,N  
      IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 240  
      PES=PES+P(I,4)    
      PQS=PQS+P(I,5)**2/P(I,4)  
  240 CONTINUE  
      FAC=(PECM-PQS)/(PES-PQS)  
      DO 260 I=1,N  
      IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 260  
      DO 250 J=1,3  
  250 P(I,J)=FAC*P(I,J) 
      P(I,4)=SQRT(P(I,5)**2+P(I,1)**2+P(I,2)**2+P(I,3)**2)  
  260 CONTINUE  
    
C...Boost back to correct reference frame.  
      CALL LUDBRB_HIJING(0,0,0.,0.,DPS(1)/DPS(4),DPS(2)/DPS(4),DPS(3)
     $     /DPS(4))  
    
      RETURN    
      END