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[u/mrichter/AliRoot.git] / HIJING / hijing1_36 / attrad.F

* $Id$

C
C
C
C****************************************************************
C	conduct soft radiation according to dipole approxiamtion
C****************************************************************
	SUBROUTINE ATTRAD(IERROR)
C
#include "hiparnt.inc"
#include "hijdat.inc"
#include "lujets_hijing.inc"
	SAVE
	IERROR=0

C.....S INVARIANT MASS-SQUARED BETWEEN PARTONS I AND I+1......
C.....SM IS THE LARGEST MASS-SQUARED....

40	SM=0.
	DO 30 I=1,N-1
	   S=2.*(P(I,4)*P(I+1,4)-P(I,1)*P(I+1,1)-P(I,2)*P(I+1,2)
     &		-P(I,3)*P(I+1,3))+P(I,5)**2+P(I+1,5)**2
	   IF(S.LT.0.) S=0.
	   WP=SQRT(S)-1.5*(P(I,5)+P(I+1,5))
	   IF(WP.GT.SM) THEN
	      PBT1=P(I,1)+P(I+1,1)
	      PBT2=P(I,2)+P(I+1,2)
	      PBT3=P(I,3)+P(I+1,3)
	      PBT4=P(I,4)+P(I+1,4)
	      BTT=(PBT1**2+PBT2**2+PBT3**2)/PBT4**2
	      IF(BTT.GE.1.0-1.0E-10) GO TO 30
	      IF((I.NE.1.OR.I.NE.N-1).AND.
     &             (K(I,2).NE.21.AND.K(I+1,2).NE.21)) GO TO 30
	      JL=I
	      SM=WP
	   ENDIF
30	CONTINUE
	S=(SM+1.5*(P(JL,5)+P(JL+1,5)))**2
      	IF(SM.LT.HIPR1(5)) GOTO 2
     
C.....MAKE PLACE FOR ONE GLUON.....
      	IF(JL+1.EQ.N) GOTO 190
      	DO 160 J=N,JL+2,-1
      		K(J+1,1)=K(J,1)
		K(J+1,2)=K(J,2)
      		DO 150 M=1,5
150   			P(J+1,M)=P(J,M)
160   		CONTINUE
190   	N=N+1
     
C.....BOOST TO REST SYSTEM FOR PARTICLES JL AND JL+1.....
      	P1=P(JL,1)+P(JL+1,1)
      	P2=P(JL,2)+P(JL+1,2)
      	P3=P(JL,3)+P(JL+1,3)
      	P4=P(JL,4)+P(JL+1,4)
      	BEX=-P1/P4
      	BEY=-P2/P4
      	BEZ=-P3/P4
	IMIN=JL
	IMAX=JL+1
      	CALL ATROBO(0.,0.,BEX,BEY,BEZ,IMIN,IMAX,IERROR)
	IF(IERROR.NE.0) RETURN
C.....ROTATE TO Z-AXIS....
        PABS=(P(JL,4)-P(JL,5))*(P(JL,4)+P(JL,5))
        IF (PABS .GT. 0) THEN
          CTH=P(JL,3)/SQRT(PABS)
        ELSE
          CTH=SIGN(1.,P(JL,3))
        ENDIF
      	IF(ABS(CTH).GT.1.0)  CTH=MAX(-1.,MIN(1.,CTH))
      	THETA=ACOS(CTH)
      	PHI=ULANGL_HIJING(P(JL,1),P(JL,2))
      	CALL ATROBO(0.,-PHI,0.,0.,0.,IMIN,IMAX,IERROR)
      	CALL ATROBO(-THETA,0.,0.,0.,0.,IMIN,IMAX,IERROR)
     
C.....CREATE ONE GLUON AND ORIENTATE.....
     
1	CALL AR3JET(S,X1,X3,JL)
      	CALL ARORIE(S,X1,X3,JL)		
	IF(HIDAT(2).GT.0.0) THEN
      	   PTG1=SQRT(P(JL,1)**2+P(JL,2)**2)
      	   PTG2=SQRT(P(JL+1,1)**2+P(JL+1,2)**2)
      	   PTG3=SQRT(P(JL+2,1)**2+P(JL+2,2)**2)
	   PTG=MAX(PTG1,PTG2,PTG3)
	   IF(PTG.GT.HIDAT(2)) THEN
	      FMFACT=EXP(-(PTG**2-HIDAT(2)**2)/HIPR1(2)**2)
	      IF(RLU_HIJING(0).GT.FMFACT) GO TO 1
	   ENDIF
	ENDIF
C.....ROTATE AND BOOST BACK.....
	IMIN=JL
	IMAX=JL+2
      	CALL ATROBO(THETA,PHI,-BEX,-BEY,-BEZ,IMIN,IMAX,IERROR)
	IF(IERROR.NE.0) RETURN
C.....ENUMERATE THE GLUONS.....
      	K(JL+2,1)=K(JL+1,1)
	K(JL+2,2)=K(JL+1,2)
	K(JL+2,3)=K(JL+1,3)
	K(JL+2,4)=K(JL+1,4)
	K(JL+2,5)=K(JL+1,5)
      	P(JL+2,5)=P(JL+1,5)
      	K(JL+1,1)=2
	K(JL+1,2)=21
	K(JL+1,3)=0
	K(JL+1,4)=0
	K(JL+1,5)=0
      	P(JL+1,5)=0.
C----THETA FUNCTION DAMPING OF THE EMITTED GLUONS. FOR HADRON-HADRON.
C----R0=VFR(2)
C      	IF(VFR(2).GT.0.) THEN
C      	PTG=SQRT(P(JL+1,1)**2+P(JL+1,2)**2)
C      	PTGMAX=WSTRI/2.
C      	DOPT=SQRT((4.*PAR(71)*VFR(2))/WSTRI)
C      	PTOPT=(DOPT*WSTRI)/(2.*VFR(2))
C      	IF(PTG.GT.PTOPT) IORDER=IORDER-1
C      	IF(PTG.GT.PTOPT) GOTO 1
C      	ENDIF
C-----
     	IF(SM.GE.HIPR1(5)) GOTO 40

2      	K(1,1)=2
	K(1,3)=0
	K(1,4)=0
	K(1,5)=0
      	K(N,1)=1
	K(N,3)=0
	K(N,4)=0
	K(N,5)=0

      	RETURN
      	END