--- /dev/null
+* $Id$
+
+C*********************************************************************
+
+ SUBROUTINE LUPREP_HIJING(IP)
+
+C...Purpose: to rearrange partons along strings, to allow small systems
+C...to collapse into one or two particles and to check flavours.
+ IMPLICIT DOUBLE PRECISION(D)
+#include "lujets_hijing.inc"
+#include "ludat1_hijing.inc"
+#include "ludat2_hijing.inc"
+#include "ludat3_hijing.inc"
+ DIMENSION DPS(5),DPC(5),UE(3)
+
+C...Rearrange parton shower product listing along strings: begin loop.
+ I1=N
+ DO 130 MQGST=1,2
+ DO 120 I=MAX(1,IP),N
+ IF(K(I,1).NE.3) GOTO 120
+ KC=LUCOMP_HIJING(K(I,2))
+ IF(KC.EQ.0) GOTO 120
+ KQ=KCHG(KC,2)
+ IF(KQ.EQ.0.OR.(MQGST.EQ.1.AND.KQ.EQ.2)) GOTO 120
+
+C...Pick up loose string end.
+ KCS=4
+ IF(KQ*ISIGN(1,K(I,2)).LT.0) KCS=5
+ IA=I
+ NSTP=0
+ 100 NSTP=NSTP+1
+ IF(NSTP.GT.4*N) THEN
+ CALL LUERRM_HIJING(14
+ $ ,'(LUPREP_HIJING:) caught in infinite loop')
+ RETURN
+ ENDIF
+
+C...Copy undecayed parton.
+ IF(K(IA,1).EQ.3) THEN
+ IF(I1.GE.MSTU(4)-MSTU(32)-5) THEN
+ CALL LUERRM_HIJING(11
+ $ ,'(LUPREP_HIJING:) no more memory left in LUJETS_HIJING'
+ $ )
+ RETURN
+ ENDIF
+ I1=I1+1
+ K(I1,1)=2
+ IF(NSTP.GE.2.AND.IABS(K(IA,2)).NE.21) K(I1,1)=1
+ K(I1,2)=K(IA,2)
+ K(I1,3)=IA
+ K(I1,4)=0
+ K(I1,5)=0
+ DO 110 J=1,5
+ P(I1,J)=P(IA,J)
+ 110 V(I1,J)=V(IA,J)
+ K(IA,1)=K(IA,1)+10
+ IF(K(I1,1).EQ.1) GOTO 120
+ ENDIF
+
+C...Go to next parton in colour space.
+ IB=IA
+ IF(MOD(K(IB,KCS)/MSTU(5)**2,2).EQ.0.AND.MOD(K(IB,KCS),MSTU(5)).
+ &NE.0) THEN
+ IA=MOD(K(IB,KCS),MSTU(5))
+ K(IB,KCS)=K(IB,KCS)+MSTU(5)**2
+ MREV=0
+ ELSE
+ IF(K(IB,KCS).GE.2*MSTU(5)**2.OR.MOD(K(IB,KCS)/MSTU(5),MSTU(5)).
+ & EQ.0) KCS=9-KCS
+ IA=MOD(K(IB,KCS)/MSTU(5),MSTU(5))
+ K(IB,KCS)=K(IB,KCS)+2*MSTU(5)**2
+ MREV=1
+ ENDIF
+ IF(IA.LE.0.OR.IA.GT.N) THEN
+ CALL LUERRM_HIJING(12
+ $ ,'(LUPREP_HIJING:) colour rearrangement failed')
+ RETURN
+ ENDIF
+ IF(MOD(K(IA,4)/MSTU(5),MSTU(5)).EQ.IB.OR.MOD(K(IA,5)/MSTU(5),
+ &MSTU(5)).EQ.IB) THEN
+ IF(MREV.EQ.1) KCS=9-KCS
+ IF(MOD(K(IA,KCS)/MSTU(5),MSTU(5)).NE.IB) KCS=9-KCS
+ K(IA,KCS)=K(IA,KCS)+2*MSTU(5)**2
+ ELSE
+ IF(MREV.EQ.0) KCS=9-KCS
+ IF(MOD(K(IA,KCS),MSTU(5)).NE.IB) KCS=9-KCS
+ K(IA,KCS)=K(IA,KCS)+MSTU(5)**2
+ ENDIF
+ IF(IA.NE.I) GOTO 100
+ K(I1,1)=1
+ 120 CONTINUE
+ 130 CONTINUE
+ N=I1
+
+C...Find lowest-mass colour singlet jet system, OK if above threshold.
+ IF(MSTJ(14).LE.0) GOTO 320
+ NS=N
+ 140 NSIN=N-NS
+ PDM=1.+PARJ(32)
+ IC=0
+ DO 190 I=MAX(1,IP),NS
+ IF(K(I,1).NE.1.AND.K(I,1).NE.2) THEN
+ ELSEIF(K(I,1).EQ.2.AND.IC.EQ.0) THEN
+ NSIN=NSIN+1
+ IC=I
+ DO 150 J=1,4
+ 150 DPS(J)=P(I,J)
+ MSTJ(93)=1
+ DPS(5)=ULMASS_HIJING(K(I,2))
+ ELSEIF(K(I,1).EQ.2) THEN
+ DO 160 J=1,4
+ 160 DPS(J)=DPS(J)+P(I,J)
+ ELSEIF(IC.NE.0.AND.KCHG(LUCOMP_HIJING(K(I,2)),2).NE.0) THEN
+ DO 170 J=1,4
+ 170 DPS(J)=DPS(J)+P(I,J)
+ MSTJ(93)=1
+ DPS(5)=DPS(5)+ULMASS_HIJING(K(I,2))
+ PD=SQRT(MAX(0D0,DPS(4)**2-DPS(1)**2-DPS(2)**2-DPS(3)**2))-DPS(5)
+ IF(PD.LT.PDM) THEN
+ PDM=PD
+ DO 180 J=1,5
+ 180 DPC(J)=DPS(J)
+ IC1=IC
+ IC2=I
+ ENDIF
+ IC=0
+ ELSE
+ NSIN=NSIN+1
+ ENDIF
+ 190 CONTINUE
+ IF(PDM.GE.PARJ(32)) GOTO 320
+
+C...Fill small-mass system as cluster.
+ NSAV=N
+ PECM=SQRT(MAX(0D0,DPC(4)**2-DPC(1)**2-DPC(2)**2-DPC(3)**2))
+ K(N+1,1)=11
+ K(N+1,2)=91
+ K(N+1,3)=IC1
+ K(N+1,4)=N+2
+ K(N+1,5)=N+3
+ P(N+1,1)=DPC(1)
+ P(N+1,2)=DPC(2)
+ P(N+1,3)=DPC(3)
+ P(N+1,4)=DPC(4)
+ P(N+1,5)=PECM
+
+C...Form two particles from flavours of lowest-mass system, if feasible.
+ K(N+2,1)=1
+ K(N+3,1)=1
+ IF(MSTU(16).NE.2) THEN
+ K(N+2,3)=N+1
+ K(N+3,3)=N+1
+ ELSE
+ K(N+2,3)=IC1
+ K(N+3,3)=IC2
+ ENDIF
+ K(N+2,4)=0
+ K(N+3,4)=0
+ K(N+2,5)=0
+ K(N+3,5)=0
+ IF(IABS(K(IC1,2)).NE.21) THEN
+ KC1=LUCOMP_HIJING(K(IC1,2))
+ KC2=LUCOMP_HIJING(K(IC2,2))
+ IF(KC1.EQ.0.OR.KC2.EQ.0) GOTO 320
+ KQ1=KCHG(KC1,2)*ISIGN(1,K(IC1,2))
+ KQ2=KCHG(KC2,2)*ISIGN(1,K(IC2,2))
+ IF(KQ1+KQ2.NE.0) GOTO 320
+ 200 CALL LUKFDI_HIJING(K(IC1,2),0,KFLN,K(N+2,2))
+ CALL LUKFDI_HIJING(K(IC2,2),-KFLN,KFLDMP,K(N+3,2))
+ IF(K(N+2,2).EQ.0.OR.K(N+3,2).EQ.0) GOTO 200
+ ELSE
+ IF(IABS(K(IC2,2)).NE.21) GOTO 320
+ 210 CALL LUKFDI_HIJING(1+INT((2.+PARJ(2))*RLU_HIJING(0)),0,KFLN
+ $ ,KFDMP)
+ CALL LUKFDI_HIJING(KFLN,0,KFLM,K(N+2,2))
+ CALL LUKFDI_HIJING(-KFLN,-KFLM,KFLDMP,K(N+3,2))
+ IF(K(N+2,2).EQ.0.OR.K(N+3,2).EQ.0) GOTO 210
+ ENDIF
+ P(N+2,5)=ULMASS_HIJING(K(N+2,2))
+ P(N+3,5)=ULMASS_HIJING(K(N+3,2))
+ IF(P(N+2,5)+P(N+3,5)+PARJ(64).GE.PECM.AND.NSIN.EQ.1) GOTO 320
+ IF(P(N+2,5)+P(N+3,5)+PARJ(64).GE.PECM) GOTO 260
+
+C...Perform two-particle decay of jet system, if possible.
+ IF(PECM.GE.0.02*DPC(4)) THEN
+ PA=SQRT((PECM**2-(P(N+2,5)+P(N+3,5))**2)*(PECM**2-
+ & (P(N+2,5)-P(N+3,5))**2))/(2.*PECM)
+ UE(3)=2.*RLU_HIJING(0)-1.
+ PHI=PARU(2)*RLU_HIJING(0)
+ UE(1)=SQRT(1.-UE(3)**2)*COS(PHI)
+ UE(2)=SQRT(1.-UE(3)**2)*SIN(PHI)
+ DO 220 J=1,3
+ P(N+2,J)=PA*UE(J)
+ 220 P(N+3,J)=-PA*UE(J)
+ P(N+2,4)=SQRT(PA**2+P(N+2,5)**2)
+ P(N+3,4)=SQRT(PA**2+P(N+3,5)**2)
+ CALL LUDBRB_HIJING(N+2,N+3,0.,0.,DPC(1)/DPC(4),DPC(2)/DPC(4),
+ & DPC(3)/DPC(4))
+ ELSE
+ NP=0
+ DO 230 I=IC1,IC2
+ 230 IF(K(I,1).EQ.1.OR.K(I,1).EQ.2) NP=NP+1
+ HA=P(IC1,4)*P(IC2,4)-P(IC1,1)*P(IC2,1)-P(IC1,2)*P(IC2,2)-
+ & P(IC1,3)*P(IC2,3)
+ IF(NP.GE.3.OR.HA.LE.1.25*P(IC1,5)*P(IC2,5)) GOTO 260
+ HD1=0.5*(P(N+2,5)**2-P(IC1,5)**2)
+ HD2=0.5*(P(N+3,5)**2-P(IC2,5)**2)
+ HR=SQRT(MAX(0.,((HA-HD1-HD2)**2-(P(N+2,5)*P(N+3,5))**2)/
+ & (HA**2-(P(IC1,5)*P(IC2,5))**2)))-1.
+ HC=P(IC1,5)**2+2.*HA+P(IC2,5)**2
+ HK1=((P(IC2,5)**2+HA)*HR+HD1-HD2)/HC
+ HK2=((P(IC1,5)**2+HA)*HR+HD2-HD1)/HC
+ DO 240 J=1,4
+ P(N+2,J)=(1.+HK1)*P(IC1,J)-HK2*P(IC2,J)
+ 240 P(N+3,J)=(1.+HK2)*P(IC2,J)-HK1*P(IC1,J)
+ ENDIF
+ DO 250 J=1,4
+ V(N+1,J)=V(IC1,J)
+ V(N+2,J)=V(IC1,J)
+ 250 V(N+3,J)=V(IC2,J)
+ V(N+1,5)=0.
+ V(N+2,5)=0.
+ V(N+3,5)=0.
+ N=N+3
+ GOTO 300
+
+C...Else form one particle from the flavours available, if possible.
+ 260 K(N+1,5)=N+2
+ IF(IABS(K(IC1,2)).GT.100.AND.IABS(K(IC2,2)).GT.100) THEN
+ GOTO 320
+ ELSEIF(IABS(K(IC1,2)).NE.21) THEN
+ CALL LUKFDI_HIJING(K(IC1,2),K(IC2,2),KFLDMP,K(N+2,2))
+ ELSE
+ KFLN=1+INT((2.+PARJ(2))*RLU_HIJING(0))
+ CALL LUKFDI_HIJING(KFLN,-KFLN,KFLDMP,K(N+2,2))
+ ENDIF
+ IF(K(N+2,2).EQ.0) GOTO 260
+ P(N+2,5)=ULMASS_HIJING(K(N+2,2))
+
+C...Find parton/particle which combines to largest extra mass.
+ IR=0
+ HA=0.
+ DO 280 MCOMB=1,3
+ IF(IR.NE.0) GOTO 280
+ DO 270 I=MAX(1,IP),N
+ IF(K(I,1).LE.0.OR.K(I,1).GT.10.OR.(I.GE.IC1.AND.I.LE.IC2.
+ &AND.K(I,1).GE.1.AND.K(I,1).LE.2)) GOTO 270
+ IF(MCOMB.EQ.1) KCI=LUCOMP_HIJING(K(I,2))
+ IF(MCOMB.EQ.1.AND.KCI.EQ.0) GOTO 270
+ IF(MCOMB.EQ.1.AND.KCHG(KCI,2).EQ.0.AND.I.LE.NS) GOTO 270
+ IF(MCOMB.EQ.2.AND.IABS(K(I,2)).GT.10.AND.IABS(K(I,2)).LE.100)
+ &GOTO 270
+ HCR=DPC(4)*P(I,4)-DPC(1)*P(I,1)-DPC(2)*P(I,2)-DPC(3)*P(I,3)
+ IF(HCR.GT.HA) THEN
+ IR=I
+ HA=HCR
+ ENDIF
+ 270 CONTINUE
+ 280 CONTINUE
+
+C...Shuffle energy and momentum to put new particle on mass shell.
+ HB=PECM**2+HA
+ HC=P(N+2,5)**2+HA
+ HD=P(IR,5)**2+HA
+C******************CHANGES BY HIJING************
+ HK2=0.0
+ IF(HA**2-(PECM*P(IR,5))**2.EQ.0.0.OR.HB+HD.EQ.0.0) GO TO 285
+C******************
+ HK2=0.5*(HB*SQRT(((HB+HC)**2-4.*(HB+HD)*P(N+2,5)**2)/
+ &(HA**2-(PECM*P(IR,5))**2))-(HB+HC))/(HB+HD)
+ 285 HK1=(0.5*(P(N+2,5)**2-PECM**2)+HD*HK2)/HB
+ DO 290 J=1,4
+ P(N+2,J)=(1.+HK1)*DPC(J)-HK2*P(IR,J)
+ P(IR,J)=(1.+HK2)*P(IR,J)-HK1*DPC(J)
+ V(N+1,J)=V(IC1,J)
+ 290 V(N+2,J)=V(IC1,J)
+ V(N+1,5)=0.
+ V(N+2,5)=0.
+ N=N+2
+
+C...Mark collapsed system and store daughter pointers. Iterate.
+ 300 DO 310 I=IC1,IC2
+ IF((K(I,1).EQ.1.OR.K(I,1).EQ.2).AND.KCHG(LUCOMP_HIJING(K(I,2))
+ $ ,2).NE.0)THEN
+ K(I,1)=K(I,1)+10
+ IF(MSTU(16).NE.2) THEN
+ K(I,4)=NSAV+1
+ K(I,5)=NSAV+1
+ ELSE
+ K(I,4)=NSAV+2
+ K(I,5)=N
+ ENDIF
+ ENDIF
+ 310 CONTINUE
+ IF(N.LT.MSTU(4)-MSTU(32)-5) GOTO 140
+
+C...Check flavours and invariant masses in parton systems.
+ 320 NP=0
+ KFN=0
+ KQS=0
+ DO 330 J=1,5
+ 330 DPS(J)=0.
+ DO 360 I=MAX(1,IP),N
+ IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 360
+ KC=LUCOMP_HIJING(K(I,2))
+ IF(KC.EQ.0) GOTO 360
+ KQ=KCHG(KC,2)*ISIGN(1,K(I,2))
+ IF(KQ.EQ.0) GOTO 360
+ NP=NP+1
+ IF(KQ.NE.2) THEN
+ KFN=KFN+1
+ KQS=KQS+KQ
+ MSTJ(93)=1
+ DPS(5)=DPS(5)+ULMASS_HIJING(K(I,2))
+ ENDIF
+ DO 340 J=1,4
+ 340 DPS(J)=DPS(J)+P(I,J)
+ IF(K(I,1).EQ.1) THEN
+ IF(NP.NE.1.AND.(KFN.EQ.1.OR.KFN.GE.3.OR.KQS.NE.0)) CALL
+ & LUERRM_HIJING(2
+ $ ,'(LUPREP_HIJING:) unphysical flavour combination')
+ IF(NP.NE.1.AND.DPS(4)**2-DPS(1)**2-DPS(2)**2-DPS(3)**2.LT.
+ & (0.9*PARJ(32)+DPS(5))**2) CALL LUERRM_HIJING(3,
+ & '(LUPREP_HIJING:) too small mass in jet system')
+ NP=0
+ KFN=0
+ KQS=0
+ DO 350 J=1,5
+ 350 DPS(J)=0.
+ ENDIF
+ 360 CONTINUE
+
+ RETURN
+ END
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff