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hijhrd.f
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hijhrd.f
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C
C
C
SUBROUTINE HIJHRD(JP,JT,JOUT,JFLG,IOPJET0)
C
C IOPTJET=1, ALL JET WILL FORM SINGLE STRING SYSTEM
C 0, ONLY Q-QBAR JET FORM SINGLE STRING SYSTEM
C*******Perform jets production and fragmentation when JP JT *******
C scatter. JOUT-> number of hard scatterings precede this one *
C for the the same pair(JP,JT). JFLG->a flag to show whether *
C jets can be produced (with valence quark=1,gluon=2, q-qbar=3)*
C or not(0). Information of jets are in COMMON/ATTJET and *
C /MINJET. ABS(NFP(JP,6)) is the total number jets produced by *
C JP. If NFP(JP,6)<0 JP can not produce jet anymore. *
C*******************************************************************
DIMENSION IP(100,2),IPQ(50),IPB(50),IT(100,2),ITQ(50),ITB(50)
COMMON/HIJCRDN/YP(3,300),YT(3,300)
SAVE /HIJCRDN/
COMMON/HIPARNT/HIPR1(100),IHPR2(50),HINT1(100),IHNT2(50)
SAVE /HIPARNT/
COMMON/HIJDAT/HIDAT0(10,10),HIDAT(10)
SAVE /HIJDAT/
COMMON/HISTRNG/NFP(300,15),PP(300,15),NFT(300,15),PT(300,15)
SAVE /HISTRNG/
COMMON/HIJJET1/NPJ(300),KFPJ(300,500),PJPX(300,500),
& PJPY(300,500),PJPZ(300,500),PJPE(300,500),
& PJPM(300,500),NTJ(300),KFTJ(300,500),
& PJTX(300,500),PJTY(300,500),PJTZ(300,500),
& PJTE(300,500),PJTM(300,500)
SAVE /HIJJET1/
COMMON/HIJJET2/NSG,NJSG(900),IASG(900,3),K1SG(900,100),
& K2SG(900,100),PXSG(900,100),PYSG(900,100),
& PZSG(900,100),PESG(900,100),PMSG(900,100)
SAVE /HIJJET2/
C+++BAC
C
C COMMON/HIJJET4/NDR,IADR(900,2),KFDR(900),PDR(900,5)
C SAVE /HIJJET4/
C
COMMON/HIJJET4/NDR,IADR(900,2),KFDR(900),PDR(900,5), VDR(900,5)
SAVE /HIJJET4/
C---BAC
COMMON/RANSEED/NSEED
SAVE /RANSEED/
C************************************ HIJING common block
COMMON/LUJETS/N,K(9000,5),P(9000,5),V(9000,5)
SAVE /LUJETS/
COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
SAVE /LUDAT1/
COMMON/PYHISUBS/MSEL,MSUB(200),KFIN(2,-40:40),CKIN(200)
SAVE /PYHISUBS/
COMMON/PYHIPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
SAVE /PYHIPARS/
COMMON/PYHIINT1/MINT(400),VINT(400)
SAVE /PYHIINT1/
COMMON/PYHIINT2/ISET(200),KFPR(200,2),COEF(200,20),ICOL(40,4,2)
SAVE /PYHIINT2/
COMMON/PYHIINT5/NGEN(0:200,3),XSEC(0:200,3)
SAVE /PYHIINT5/
COMMON/HIPYINT/MINT4,MINT5,ATCO(200,20),ATXS(0:200)
SAVE /HIPYINT/
C*********************************** LU common block
MXJT=500
C SIZE OF COMMON BLOCK FOR # OF PARTON PER STRING
MXSG=900
C SIZE OF COMMON BLOCK FOR # OF SINGLE STRINGS
MXSJ=100
C SIZE OF COMMON BLOCK FOR # OF PARTON PER SINGLE
C STRING
JFLG=0
IHNT2(11)=JP
IHNT2(12)=JT
C
IOPJET=IOPJET0
IF(IOPJET.EQ.1.AND.(NFP(JP,6).NE.0.OR.NFT(JT,6).NE.0))
& IOPJET=0
IF(JP.GT.IHNT2(1) .OR. JT.GT.IHNT2(3)) RETURN
IF(NFP(JP,6).LT.0 .OR. NFT(JT,6).LT.0) RETURN
C ******** JP or JT can not produce jet anymore
C
IF(JOUT.EQ.0) THEN
EPP=PP(JP,4)+PP(JP,3)
EPM=PP(JP,4)-PP(JP,3)
ETP=PT(JT,4)+PT(JT,3)
ETM=PT(JT,4)-PT(JT,3)
IF(EPP.LT.0.0) GO TO 1000
IF(EPM.LT.0.0) GO TO 1000
IF(ETP.LT.0.0) GO TO 1000
IF(ETM.LT.0.0) GO TO 1000
IF(EPP/(EPM+0.01).LE.ETP/(ETM+0.01)) RETURN
ENDIF
C ********for the first hard scattering of (JP,JT)
C have collision only when Ycm(JP)>Ycm(JT)
ECUT1=HIPR1(1)+HIPR1(8)+PP(JP,14)+PP(JP,15)
ECUT2=HIPR1(1)+HIPR1(8)+PT(JT,14)+PT(JT,15)
IF(PP(JP,4).LE.ECUT1) THEN
NFP(JP,6)=-ABS(NFP(JP,6))
RETURN
ENDIF
IF(PT(JT,4).LE.ECUT2) THEN
NFT(JT,6)=-ABS(NFT(JT,6))
RETURN
ENDIF
C *********must have enough energy to produce jets
MISS=0
MISP=0
MIST=0
C
IF(NFP(JP,10).EQ.0 .AND. NFT(JT,10).EQ.0) THEN
MINT(44)=MINT4
MINT(45)=MINT5
XSEC(0,1)=ATXS(0)
XSEC(11,1)=ATXS(11)
XSEC(12,1)=ATXS(12)
XSEC(28,1)=ATXS(28)
DO 120 I=1,20
COEF(11,I)=ATCO(11,I)
COEF(12,I)=ATCO(12,I)
COEF(28,I)=ATCO(28,I)
120 CONTINUE
ELSE
ISUB11=0
ISUB12=0
ISUB28=0
IF(XSEC(11,1).NE.0) ISUB11=1
IF(XSEC(12,1).NE.0) ISUB12=1
IF(XSEC(28,1).NE.0) ISUB28=1
MINT(44)=MINT4-ISUB11-ISUB12-ISUB28
MINT(45)=MINT5-ISUB11-ISUB12-ISUB28
XSEC(0,1)=ATXS(0)-ATXS(11)-ATXS(12)-ATXS(28)
XSEC(11,1)=0.0
XSEC(12,1)=0.0
XSEC(28,1)=0.0
DO 110 I=1,20
COEF(11,I)=0.0
COEF(12,I)=0.0
COEF(28,I)=0.0
110 CONTINUE
ENDIF
C ********Scatter the valence quarks only once per NN
C collision,
C afterwards only gluon can have hard scattering.
155 CALL PYHITHIA
JJ=MINT(31)
IF(JJ.NE.1) GO TO 155
C *********one hard collision at a time
IF(K(7,2).EQ.-K(8,2)) THEN
QMASS2=(P(7,4)+P(8,4))**2-(P(7,1)+P(8,1))**2
& -(P(7,2)+P(8,2))**2-(P(7,3)+P(8,3))**2
QM=ULMASS(K(7,2))
IF(QMASS2.LT.(2.0*QM+HIPR1(1))**2) GO TO 155
ENDIF
C ********q-qbar jets must has minimum mass HIPR1(1)
PXP=PP(JP,1)-P(3,1)
PYP=PP(JP,2)-P(3,2)
PZP=PP(JP,3)-P(3,3)
PEP=PP(JP,4)-P(3,4)
PXT=PT(JT,1)-P(4,1)
PYT=PT(JT,2)-P(4,2)
PZT=PT(JT,3)-P(4,3)
PET=PT(JT,4)-P(4,4)
IF(PEP.LE.ECUT1) THEN
MISP=MISP+1
IF(MISP.LT.50) GO TO 155
NFP(JP,6)=-ABS(NFP(JP,6))
RETURN
ENDIF
IF(PET.LE.ECUT2) THEN
MIST=MIST+1
IF(MIST.LT.50) GO TO 155
NFT(JT,6)=-ABS(NFT(JT,6))
RETURN
ENDIF
C ******** if the remain energy<ECUT the proj or targ
C can not produce jet anymore
WP=PEP+PZP+PET+PZT
WM=PEP-PZP+PET-PZT
IF(WP.LT.0.0 .OR. WM.LT.0.0) THEN
MISS=MISS+1
IF(MISS.LT.50) GO TO 155
RETURN
ENDIF
C ********the total W+, W- must be positive
SW=WP*WM
AMPX=SQRT((ECUT1-HIPR1(8))**2+PXP**2+PYP**2+0.01)
AMTX=SQRT((ECUT2-HIPR1(8))**2+PXT**2+PYT**2+0.01)
SXX=(AMPX+AMTX)**2
IF(SW.LT.SXX.OR.VINT(43).LT.HIPR1(1)) THEN
MISS=MISS+1
IF(MISS.LT.50) GO TO 155
RETURN
ENDIF
C ********the proj and targ remnants must have at least
C a CM energy that can produce two strings
C with minimum mass HIPR1(1)(see HIJSFT HIJFRG)
C
HINT1(41)=P(7,1)
HINT1(42)=P(7,2)
HINT1(43)=P(7,3)
HINT1(44)=P(7,4)
HINT1(45)=P(7,5)
HINT1(46)=SQRT(P(7,1)**2+P(7,2)**2)
HINT1(51)=P(8,1)
HINT1(52)=P(8,2)
HINT1(53)=P(8,3)
HINT1(54)=P(8,4)
HINT1(55)=P(8,5)
HINT1(56)=SQRT(P(8,1)**2+P(8,2)**2)
IHNT2(14)=K(7,2)
IHNT2(15)=K(8,2)
C
PINIRAD=(1.0-EXP(-2.0*(VINT(47)-HIDAT(1))))
& /(1.0+EXP(-2.0*(VINT(47)-HIDAT(1))))
I_INIRAD=0
IF(ATL_RAN(NSEED).LE.PINIRAD) I_INIRAD=1
IF(K(7,2).EQ.-K(8,2)) GO TO 190
IF(K(7,2).EQ.21.AND.K(8,2).EQ.21.AND.IOPJET.EQ.1) GO TO 190
C*******************************************************************
C gluon jets are going to be connectd with
C the final leading string of quark-aintquark
C*******************************************************************
JFLG=2
JPP=0
LPQ=0
LPB=0
JTT=0
LTQ=0
LTB=0
IS7=0
IS8=0
HINT1(47)=0.0
HINT1(48)=0.0
HINT1(49)=0.0
HINT1(50)=0.0
HINT1(67)=0.0
HINT1(68)=0.0
HINT1(69)=0.0
HINT1(70)=0.0
DO 180 I=9,N
IF(K(I,3).EQ.1 .OR. K(I,3).EQ.2.OR.
& ABS(K(I,2)).GT.30) GO TO 180
C************************************************************
IF(K(I,3).EQ.7) THEN
HINT1(47)=HINT1(47)+P(I,1)
HINT1(48)=HINT1(48)+P(I,2)
HINT1(49)=HINT1(49)+P(I,3)
HINT1(50)=HINT1(50)+P(I,4)
ENDIF
IF(K(I,3).EQ.8) THEN
HINT1(67)=HINT1(67)+P(I,1)
HINT1(68)=HINT1(68)+P(I,2)
HINT1(69)=HINT1(69)+P(I,3)
HINT1(70)=HINT1(70)+P(I,4)
ENDIF
C************************modifcation made on Apr 10. 1996*****
IF(K(I,2).GT.21.AND.K(I,2).LE.30) THEN
NDR=NDR+1
IADR(NDR,1)=JP
IADR(NDR,2)=JT
KFDR(NDR)=K(I,2)
PDR(NDR,1)=P(I,1)
PDR(NDR,2)=P(I,2)
PDR(NDR,3)=P(I,3)
PDR(NDR,4)=P(I,4)
PDR(NDR,5)=P(I,5)
VDR(NDR,1)=V(I,1)
VDR(NDR,2)=V(I,2)
VDR(NDR,3)=V(I,3)
VDR(NDR,4)=V(I,4)
C************************************************************
GO TO 180
C************************correction made on Oct. 14,1994*****
ENDIF
IF(K(I,3).EQ.7.OR.K(I,3).EQ.3) THEN
IF(K(I,3).EQ.7.AND.K(I,2).NE.21.AND.K(I,2).EQ.K(7,2)
& .AND.IS7.EQ.0) THEN
PP(JP,10)=P(I,1)
PP(JP,11)=P(I,2)
PP(JP,12)=P(I,3)
PZP=PZP+P(I,3)
PEP=PEP+P(I,4)
NFP(JP,10)=1
IS7=1
GO TO 180
ENDIF
IF(K(I,3).EQ.3.AND.(K(I,2).NE.21.OR.
& I_INIRAD.EQ.0)) THEN
PXP=PXP+P(I,1)
PYP=PYP+P(I,2)
PZP=PZP+P(I,3)
PEP=PEP+P(I,4)
GO TO 180
ENDIF
JPP=JPP+1
IP(JPP,1)=I
IP(JPP,2)=0
IF(K(I,2).NE.21) THEN
IF(K(I,2).GT.0) THEN
LPQ=LPQ+1
IPQ(LPQ)=JPP
IP(JPP,2)=LPQ
ELSE IF(K(I,2).LT.0) THEN
LPB=LPB+1
IPB(LPB)=JPP
IP(JPP,2)=-LPB
ENDIF
ENDIF
ELSE IF(K(I,3).EQ.8.OR.K(I,3).EQ.4) THEN
IF(K(I,3).EQ.8.AND.K(I,2).NE.21.AND.K(I,2).EQ.K(8,2)
& .AND.IS8.EQ.0) THEN
PT(JT,10)=P(I,1)
PT(JT,11)=P(I,2)
PT(JT,12)=P(I,3)
PZT=PZT+P(I,3)
PET=PET+P(I,4)
NFT(JT,10)=1
IS8=1
GO TO 180
ENDIF
IF(K(I,3).EQ.4.AND.(K(I,2).NE.21.OR.
& I_INIRAD.EQ.0)) THEN
PXT=PXT+P(I,1)
PYT=PYT+P(I,2)
PZT=PZT+P(I,3)
PET=PET+P(I,4)
GO TO 180
ENDIF
JTT=JTT+1
IT(JTT,1)=I
IT(JTT,2)=0
IF(K(I,2).NE.21) THEN
IF(K(I,2).GT.0) THEN
LTQ=LTQ+1
ITQ(LTQ)=JTT
IT(JTT,2)=LTQ
ELSE IF(K(I,2).LT.0) THEN
LTB=LTB+1
ITB(LTB)=JTT
IT(JTT,2)=-LTB
ENDIF
ENDIF
ENDIF
180 CONTINUE
c
c
IF(LPQ.NE.LPB .OR. LTQ.NE.LTB) THEN
MISS=MISS+1
IF(MISS.LE.50) GO TO 155
WRITE(6,*) ' Q -QBAR NOT MATCHED IN HIJHRD'
JFLG=0
RETURN
ENDIF
C****The following will rearrange the partons so that a quark is***
C****allways followed by an anti-quark ****************************
J=0
181 J=J+1
IF(J.GT.JPP) GO TO 182
IF(IP(J,2).EQ.0) THEN
GO TO 181
ELSE IF(IP(J,2).NE.0) THEN
LP=ABS(IP(J,2))
IP1=IP(J,1)
IP2=IP(J,2)
IP(J,1)=IP(IPQ(LP),1)
IP(J,2)=IP(IPQ(LP),2)
IP(IPQ(LP),1)=IP1
IP(IPQ(LP),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPQ(LP)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPQ(LP)
ENDIF
C ********replace J with a quark
IP1=IP(J+1,1)
IP2=IP(J+1,2)
IP(J+1,1)=IP(IPB(LP),1)
IP(J+1,2)=IP(IPB(LP),2)
IP(IPB(LP),1)=IP1
IP(IPB(LP),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPB(LP)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPB(LP)
ENDIF
C ******** replace J+1 with anti-quark
J=J+1
GO TO 181
ENDIF
182 J=0
183 J=J+1
IF(J.GT.JTT) GO TO 184
IF(IT(J,2).EQ.0) THEN
GO TO 183
ELSE IF(IT(J,2).NE.0) THEN
LT=ABS(IT(J,2))
IT1=IT(J,1)
IT2=IT(J,2)
IT(J,1)=IT(ITQ(LT),1)
IT(J,2)=IT(ITQ(LT),2)
IT(ITQ(LT),1)=IT1
IT(ITQ(LT),2)=IT2
IF(IT2.GT.0) THEN
ITQ(IT2)=ITQ(LT)
ELSE IF(IT2.LT.0) THEN
ITB(-IT2)=ITQ(LT)
ENDIF
C ********replace J with a quark
IT1=IT(J+1,1)
IT2=IT(J+1,2)
IT(J+1,1)=IT(ITB(LT),1)
IT(J+1,2)=IT(ITB(LT),2)
IT(ITB(LT),1)=IT1
IT(ITB(LT),2)=IT2
IF(IT2.GT.0) THEN
ITQ(IT2)=ITB(LT)
ELSE IF(IT2.LT.0) THEN
ITB(-IT2)=ITB(LT)
ENDIF
C ******** replace J+1 with anti-quark
J=J+1
GO TO 183
ENDIF
184 CONTINUE
IF(NPJ(JP)+JPP.GT.MXJT.OR.NTJ(JT)+JTT.GT.MXJT) THEN
JFLG=0
WRITE(6,*) 'number of partons per string exceeds'
WRITE(6,*) 'the common block size'
RETURN
ENDIF
C ********check the bounds of common blocks
DO 186 J=1,JPP
KFPJ(JP,NPJ(JP)+J)=K(IP(J,1),2)
PJPX(JP,NPJ(JP)+J)=P(IP(J,1),1)
PJPY(JP,NPJ(JP)+J)=P(IP(J,1),2)
PJPZ(JP,NPJ(JP)+J)=P(IP(J,1),3)
PJPE(JP,NPJ(JP)+J)=P(IP(J,1),4)
PJPM(JP,NPJ(JP)+J)=P(IP(J,1),5)
186 CONTINUE
NPJ(JP)=NPJ(JP)+JPP
DO 188 J=1,JTT
KFTJ(JT,NTJ(JT)+J)=K(IT(J,1),2)
PJTX(JT,NTJ(JT)+J)=P(IT(J,1),1)
PJTY(JT,NTJ(JT)+J)=P(IT(J,1),2)
PJTZ(JT,NTJ(JT)+J)=P(IT(J,1),3)
PJTE(JT,NTJ(JT)+J)=P(IT(J,1),4)
PJTM(JT,NTJ(JT)+J)=P(IT(J,1),5)
188 CONTINUE
NTJ(JT)=NTJ(JT)+JTT
GO TO 900
C*****************************************************************
CThis is the case of a quark-antiquark jet it will fragment alone
C****************************************************************
190 JFLG=3
IF(K(7,2).NE.21.AND.K(8,2).NE.21.AND.
& K(7,2)*K(8,2).GT.0) GO TO 155
JPP=0
LPQ=0
LPB=0
DO 200 I=9,N
IF(K(I,3).EQ.1.OR.K(I,3).EQ.2.OR.
& ABS(K(I,2)).GT.30) GO TO 200
IF(K(I,2).GT.21.AND.K(I,2).LE.30) THEN
NDR=NDR+1
IADR(NDR,1)=JP
IADR(NDR,2)=JT
KFDR(NDR)=K(I,2)
PDR(NDR,1)=P(I,1)
PDR(NDR,2)=P(I,2)
PDR(NDR,3)=P(I,3)
PDR(NDR,4)=P(I,4)
PDR(NDR,5)=P(I,5)
VDR(NDR,1)=V(I,1)
VDR(NDR,2)=V(I,2)
VDR(NDR,3)=V(I,3)
VDR(NDR,4)=V(I,4)
C************************************************************
GO TO 200
C************************correction made on Oct. 14,1994*****
ENDIF
IF(K(I,3).EQ.3.AND.(K(I,2).NE.21.OR.
& I_INIRAD.EQ.0)) THEN
PXP=PXP+P(I,1)
PYP=PYP+P(I,2)
PZP=PZP+P(I,3)
PEP=PEP+P(I,4)
GO TO 200
ENDIF
IF(K(I,3).EQ.4.AND.(K(I,2).NE.21.OR.
& I_INIRAD.EQ.0)) THEN
PXT=PXT+P(I,1)
PYT=PYT+P(I,2)
PZT=PZT+P(I,3)
PET=PET+P(I,4)
GO TO 200
ENDIF
JPP=JPP+1
IP(JPP,1)=I
IP(JPP,2)=0
IF(K(I,2).NE.21) THEN
IF(K(I,2).GT.0) THEN
LPQ=LPQ+1
IPQ(LPQ)=JPP
IP(JPP,2)=LPQ
ELSE IF(K(I,2).LT.0) THEN
LPB=LPB+1
IPB(LPB)=JPP
IP(JPP,2)=-LPB
ENDIF
ENDIF
200 CONTINUE
IF(LPQ.NE.LPB) THEN
MISS=MISS+1
IF(MISS.LE.50) GO TO 155
WRITE(6,*) LPQ,LPB, 'Q-QBAR NOT CONSERVED OR NOT MATCHED'
JFLG=0
RETURN
ENDIF
C**** The following will rearrange the partons so that a quark is***
C**** allways followed by an anti-quark ****************************
J=0
220 J=J+1
IF(J.GT.JPP) GO TO 222
IF(IP(J,2).EQ.0) GO TO 220
LP=ABS(IP(J,2))
IP1=IP(J,1)
IP2=IP(J,2)
IP(J,1)=IP(IPQ(LP),1)
IP(J,2)=IP(IPQ(LP),2)
IP(IPQ(LP),1)=IP1
IP(IPQ(LP),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPQ(LP)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPQ(LP)
ENDIF
IPQ(LP)=J
C ********replace J with a quark
IP1=IP(J+1,1)
IP2=IP(J+1,2)
IP(J+1,1)=IP(IPB(LP),1)
IP(J+1,2)=IP(IPB(LP),2)
IP(IPB(LP),1)=IP1
IP(IPB(LP),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPB(LP)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPB(LP)
ENDIF
C ******** replace J+1 with an anti-quark
IPB(LP)=J+1
J=J+1
GO TO 220
222 CONTINUE
IF(LPQ.GE.1) THEN
DO 240 L0=2,LPQ
IP1=IP(2*L0-3,1)
IP2=IP(2*L0-3,2)
IP(2*L0-3,1)=IP(IPQ(L0),1)
IP(2*L0-3,2)=IP(IPQ(L0),2)
IP(IPQ(L0),1)=IP1
IP(IPQ(L0),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPQ(L0)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPQ(L0)
ENDIF
IPQ(L0)=2*L0-3
C
IP1=IP(2*L0-2,1)
IP2=IP(2*L0-2,2)
IP(2*L0-2,1)=IP(IPB(L0),1)
IP(2*L0-2,2)=IP(IPB(L0),2)
IP(IPB(L0),1)=IP1
IP(IPB(L0),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPB(L0)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPB(L0)
ENDIF
IPB(L0)=2*L0-2
240 CONTINUE
C ********move all the qqbar pair to the front of
C the list, except the first pair
IP1=IP(2*LPQ-1,1)
IP2=IP(2*LPQ-1,2)
IP(2*LPQ-1,1)=IP(IPQ(1),1)
IP(2*LPQ-1,2)=IP(IPQ(1),2)
IP(IPQ(1),1)=IP1
IP(IPQ(1),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPQ(1)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPQ(1)
ENDIF
IPQ(1)=2*LPQ-1
C ********move the first quark to the beginning of
C the last string system
IP1=IP(JPP,1)
IP2=IP(JPP,2)
IP(JPP,1)=IP(IPB(1),1)
IP(JPP,2)=IP(IPB(1),2)
IP(IPB(1),1)=IP1
IP(IPB(1),2)=IP2
IF(IP2.GT.0) THEN
IPQ(IP2)=IPB(1)
ELSE IF(IP2.LT.0) THEN
IPB(-IP2)=IPB(1)
ENDIF
IPB(1)=JPP
C ********move the first anti-quark to the end of the
C last string system
ENDIF
IF(NSG.GE.MXSG) THEN
JFLG=0
WRITE(6,*) 'number of jets forming single strings exceeds'
WRITE(6,*) 'the common block size'
RETURN
ENDIF
IF(JPP.GT.MXSJ) THEN
JFLG=0
WRITE(6,*) 'number of partons per single jet system'
WRITE(6,*) 'exceeds the common block size'
RETURN
ENDIF
C ********check the bounds of common block size
NSG=NSG+1
NJSG(NSG)=JPP
IASG(NSG,1)=JP
IASG(NSG,2)=JT
IASG(NSG,3)=0
DO 300 I=1,JPP
K1SG(NSG,I)=2
K2SG(NSG,I)=K(IP(I,1),2)
IF(K2SG(NSG,I).LT.0) K1SG(NSG,I)=1
PXSG(NSG,I)=P(IP(I,1),1)
PYSG(NSG,I)=P(IP(I,1),2)
PZSG(NSG,I)=P(IP(I,1),3)
PESG(NSG,I)=P(IP(I,1),4)
PMSG(NSG,I)=P(IP(I,1),5)
300 CONTINUE
K1SG(NSG,1)=2
K1SG(NSG,JPP)=1
C******* reset the energy-momentum of incoming particles ********
900 PP(JP,1)=PXP
PP(JP,2)=PYP
PP(JP,3)=PZP
PP(JP,4)=PEP
PP(JP,5)=0.0
PT(JT,1)=PXT
PT(JT,2)=PYT
PT(JT,3)=PZT
PT(JT,4)=PET
PT(JT,5)=0.0
NFP(JP,6)=NFP(JP,6)+1
NFT(JT,6)=NFT(JT,6)+1
RETURN
C
1000 JFLG=-1
IF(IHPR2(10).EQ.0) RETURN
WRITE(6,*) 'Fatal HIJHRD error'
WRITE(6,*) JP, ' proj E+,E-',EPP,EPM,' status',NFP(JP,5)
WRITE(6,*) JT, ' targ E+,E_',ETP,ETM,' status',NFT(JT,5)
RETURN
END