* $Id$
    
C*********************************************************************  
C THIS SUBROUTINE IS ONLY FOR THE USE OF HIJING TO ROTATE OR BOOST
C	THE FOUR MOMENTUM ONLY
C*********************************************************************
    
      SUBROUTINE HIROBO(THE,PHI,BEX,BEY,BEZ)    
    
C...Purpose: to perform rotations and boosts.   
      IMPLICIT DOUBLE PRECISION(D)  
#include "lujets_hijing.inc"
#include "ludat1_hijing.inc"
      DIMENSION ROT(3,3),PR(3),VR(3),DP(4),DV(4)    
    
C...Find range of rotation/boost. Convert boost to double precision.    
      IMIN=1    
      IF(MSTU(1).GT.0) IMIN=MSTU(1) 
      IMAX=N    
      IF(MSTU(2).GT.0) IMAX=MSTU(2) 
      DBX=BEX   
      DBY=BEY   
      DBZ=BEZ   
    
C...Check range of rotation/boost.  
      IF(IMIN.GT.MSTU(4).OR.IMAX.GT.MSTU(4)) THEN   
         CALL LUERRM_HIJING(11
     $        ,'(LUROBO_HIJING:) range outside LUJETS_HIJING memory') 
        RETURN  
      ENDIF 
    
C...Rotate, typically from z axis to direction (theta,phi). 
      IF(THE**2+PHI**2.GT.1E-20) THEN   
        ROT(1,1)=COS(THE)*COS(PHI)  
        ROT(1,2)=-SIN(PHI)  
        ROT(1,3)=SIN(THE)*COS(PHI)  
        ROT(2,1)=COS(THE)*SIN(PHI)  
        ROT(2,2)=COS(PHI)   
        ROT(2,3)=SIN(THE)*SIN(PHI)  
        ROT(3,1)=-SIN(THE)  
        ROT(3,2)=0. 
        ROT(3,3)=COS(THE)   
        DO 130 I=IMIN,IMAX  
        IF(K(I,1).LE.0) GOTO 130    
        DO 110 J=1,3    
  110   PR(J)=P(I,J)   
        DO 120 J=1,3    
  120   P(I,J)=ROT(J,1)*PR(1)+ROT(J,2)*PR(2)+ROT(J,3)*PR(3) 
  130   CONTINUE    
      ENDIF 
    
C...Boost, typically from rest to momentum/energy=beta. 
      IF(DBX**2+DBY**2+DBZ**2.GT.1E-20) THEN    
        DB=SQRT(DBX**2+DBY**2+DBZ**2)   
        IF(DB.GT.0.99999999D0) THEN 
C...Rescale boost vector if too close to unity. 
           CALL LUERRM_HIJING(3
     $          ,'(LUROBO_HIJING:) boost vector too large') 
          DBX=DBX*(0.99999999D0/DB) 
          DBY=DBY*(0.99999999D0/DB) 
          DBZ=DBZ*(0.99999999D0/DB) 
          DB=0.99999999D0   
        ENDIF   
        DGA=1D0/SQRT(1D0-DB**2) 
        DO 150 I=IMIN,IMAX  
        IF(K(I,1).LE.0) GOTO 150    
        DO 140 J=1,4    
  140   DP(J)=P(I,J)    
        DBP=DBX*DP(1)+DBY*DP(2)+DBZ*DP(3)   
        DGABP=DGA*(DGA*DBP/(1D0+DGA)+DP(4)) 
        P(I,1)=DP(1)+DGABP*DBX  
        P(I,2)=DP(2)+DGABP*DBY  
        P(I,3)=DP(3)+DGABP*DBZ  
        P(I,4)=DGA*(DP(4)+DBP)  
  150   CONTINUE    
      ENDIF 
    
      RETURN    
      END