HIJING/hijing1_36/hijsft.F

   1 * $Id$
   2 C
   3 C
   4 C*******************************************************************
   5 C                                                                  *
   6 C               Subroutine HIJSFT                                  *
   7 C                                                                  *
   8 C  Scatter two excited strings, JP from proj and JT from target    *
   9 C*******************************************************************
  10         SUBROUTINE HIJSFT(JP,JT,JOUT,IERROR)
  11 #include "hijcrdn.inc"
  12 #include "hiparnt.inc"
  13 #include "hijdat.inc"
  14 #include "hijjet1.inc"
  15 #include "hijjet2.inc"
  16 #include "histrng.inc"
  17 #include "dpmcom1.inc"
  18 #include "dpmcom2.inc"
  19         SAVE
  20 C*******************************************************************
  21 C       JOUT-> the number
  22 C       of hard scatterings preceding this soft collision.
  23 C       IHNT2(13)-> 1=
  24 C       double diffrac 2=single diffrac, 3=non-single diffrac.
  25 C*******************************************************************
  26         IERROR=0
  27         JJP=JP
  28         JJT=JT
  29         NDPM=0
  30         IOPMAIN=0
  31         IF(JP.GT.IHNT2(1) .OR. JT.GT.IHNT2(3)) RETURN
  32
  33         EPP=PP(JP,4)+PP(JP,3)
  34         EPM=PP(JP,4)-PP(JP,3)
  35         ETP=PT(JT,4)+PT(JT,3)
  36         ETM=PT(JT,4)-PT(JT,3)
  37
  38         WP=EPP+ETP
  39         WM=EPM+ETM
  40         SW=WP*WM
  41 C               ********total W+,W- and center-of-mass energy
  42
  43         IF(WP.LT.0.0 .OR. WM.LT.0.0) GO TO 1000
  44
  45         IF(JOUT.EQ.0) THEN
  46                 IF(EPP.LT.0.0) GO TO 1000
  47                 IF(EPM.LT.0.0) GO TO 1000
  48                 IF(ETP.LT.0.0) GO TO 1000
  49                 IF(ETM.LT.0.0) GO TO 1000
  50                 IF(EPP/(EPM+0.01).LE.ETP/(ETM+0.01)) RETURN
  51         ENDIF
  52 C               ********For strings which does not follow a jet-prod,
  53 C                       scatter only if Ycm(JP)>Ycm(JT). When jets
  54 C                       are produced just before this collision
  55 C                       this requirement has already be enforced
  56 C                       (see SUBROUTINE HIJHRD)
  57         IHNT2(11)=JP
  58         IHNT2(12)=JT
  59 C
  60 C
  61 C
  62         MISS=0
  63         PKC1=0.0
  64         PKC2=0.0
  65         PKC11=0.0
  66         PKC12=0.0
  67         PKC21=0.0
  68         PKC22=0.0
  69         DPKC11=0.0
  70         DPKC12=0.0
  71         DPKC21=0.0
  72         DPKC22=0.0
  73         IF(NFP(JP,10).EQ.1.OR.NFT(JT,10).EQ.1) THEN
  74            IF(NFP(JP,10).EQ.1) THEN
  75               PHI1=ULANGL_HIJING(PP(JP,10),PP(JP,11))
  76               PPJET=SQRT(PP(JP,10)**2+PP(JP,11)**2)
  77               PKC1=PPJET
  78               PKC11=PP(JP,10)
  79               PKC12=PP(JP,11)
  80            ENDIF
  81            IF(NFT(JT,10).EQ.1) THEN
  82               PHI2=ULANGL_HIJING(PT(JT,10),PT(JT,11))
  83               PTJET=SQRT(PT(JT,10)**2+PT(JT,11)**2)
  84               PKC2=PTJET
  85               PKC21=PT(JT,10)
  86               PKC22=PT(JT,11)
  87            ENDIF
  88            IF(IHPR2(4).GT.0.AND.IHNT2(1).GT.1.AND.IHNT2(3).GT.1) THEN
  89               IF(NFP(JP,10).EQ.0) THEN
  90                  PHI=-PHI2
  91               ELSE IF(NFT(JT,10).EQ.0) THEN
  92                  PHI=PHI1
  93               ELSE
  94                  PHI=(PHI1+PHI2-HIPR1(40))/2.0
  95               ENDIF
  96               BX=HINT1(19)*COS(HINT1(20))
  97               BY=HINT1(19)*SIN(HINT1(20))
  98               XP0=YP(1,JP)
  99               YP0=YP(2,JP)
 100               XT0=YT(1,JT)+BX
 101               YT0=YT(2,JT)+BY
 102               R1=MAX(1.2*IHNT2(1)**0.3333333,
 103      &               SQRT(XP0**2+YP0**2))
 104               R2=MAX(1.2*IHNT2(3)**0.3333333,
 105      &               SQRT((XT0-BX)**2+(YT0-BY)**2))
 106               IF(ABS(COS(PHI)).LT.1.0E-5) THEN
 107                  DD1=R1
 108                  DD2=R1
 109 C PH             DD3=ABS(BY+SQRT(R2**2-(XP0-BX)**2)-YP0)
 110 C PH             DD4=ABS(BY-SQRT(R2**2-(XP0-BX)**2)-YP0)
 111                  DD3=ABS(BY+SQRT(R2**2-(XT0-BX)**2)-YP0)
 112                  DD4=ABS(BY-SQRT(R2**2-(XT0-BX)**2)-YP0)
 113                  GO TO 5
 114               ENDIF
 115               BB=2.0*SIN(PHI)*(COS(PHI)*YP0-SIN(PHI)*XP0)
 116               CC=(YP0**2-R1**2)*COS(PHI)**2+XP0*SIN(PHI)*(
 117      &                          XP0*SIN(PHI)-2.0*YP0*COS(PHI))
 118               DD=BB**2-4.0*CC
 119               IF(DD.LT.0.0) GO TO 10
 120               XX1=(-BB+SQRT(DD))/2.0
 121               XX2=(-BB-SQRT(DD))/2.0
 122               DD1=ABS((XX1-XP0)/COS(PHI))
 123               DD2=ABS((XX2-XP0)/COS(PHI))
 124 C
 125               BB=2.0*SIN(PHI)*(COS(PHI)*(YT0-BY)-SIN(PHI)*XT0)-2.0*BX
 126               CC=(BX**2+(YT0-BY)**2-R2**2)*COS(PHI)**2+XT0*SIN(PHI)
 127      &           *(XT0*SIN(PHI)-2.0*COS(PHI)*(YT0-BY))
 128      &           -2.0*BX*SIN(PHI)*(COS(PHI)*(YT0-BY)-SIN(PHI)*XT0)
 129               DD=BB**2-4.0*CC
 130               IF(DD.LT.0.0) GO TO 10
 131               XX1=(-BB+SQRT(DD))/2.0
 132               XX2=(-BB-SQRT(DD))/2.0
 133               DD3=ABS((XX1-XT0)/COS(PHI))
 134               DD4=ABS((XX2-XT0)/COS(PHI))
 135 C
 136  5            DD1=MIN(DD1,DD3)
 137               DD2=MIN(DD2,DD4)
 138               IF(DD1.LT.HIPR1(13)) DD1=0.0
 139               IF(DD2.LT.HIPR1(13)) DD2=0.0
 140               IF(NFP(JP,10).EQ.1.AND.PPJET.GT.HIPR1(11)) THEN
 141                  IF (IHPR2(50) .EQ. 1) THEN
 142                     DEDX0 = HIPR1(14)*LOG10(PPJET)/LOG10(5.)
 143                  ELSE
 144                     DEDX0 = HIPR1(14)
 145                  ENDIF
 146                  DP1=DD1*DEDX0/2.0
 147                  DP1=MIN(DP1,PPJET-HIPR1(11))
 148                  PKC1=PPJET-DP1
 149                  DPX1=COS(PHI1)*DP1
 150                  DPY1=SIN(PHI1)*DP1
 151                  PKC11=PP(JP,10)-DPX1
 152                  PKC12=PP(JP,11)-DPY1
 153                  IF(DP1.GT.0.0) THEN
 154                     CTHEP=PP(JP,12)/SQRT(PP(JP,12)**2+PPJET**2)
 155                     DPZ1=DP1*CTHEP/SQRT(1.0-CTHEP**2)
 156                     DPE1=SQRT(DPX1**2+DPY1**2+DPZ1**2)
 157                     EPPPRM=PP(JP,4)+PP(JP,3)-DPE1-DPZ1
 158                     EPMPRM=PP(JP,4)-PP(JP,3)-DPE1+DPZ1
 159                     IF(EPPPRM.LE.0.0.OR.EPMPRM.LE.0.0) GO TO 15
 160                     EPP=EPPPRM
 161                     EPM=EPMPRM
 162                     PP(JP,10)=PKC11
 163                     PP(JP,11)=PKC12
 164                     NPJ(JP)=NPJ(JP)+1
 165                     KFPJ(JP,NPJ(JP))=21
 166                     PJPX(JP,NPJ(JP))=DPX1
 167                     PJPY(JP,NPJ(JP))=DPY1
 168                     PJPZ(JP,NPJ(JP))=DPZ1
 169                     PJPE(JP,NPJ(JP))=DPE1
 170                     PJPM(JP,NPJ(JP))=0.0
 171                     PP(JP,3)=PP(JP,3)-DPZ1
 172                     PP(JP,4)=PP(JP,4)-DPE1
 173                  ENDIF
 174               ENDIF
 175  15           IF(NFT(JT,10).EQ.1.AND.PTJET.GT.HIPR1(11)) THEN
 176                  IF (IHPR2(50) .EQ. 1) THEN
 177                     DEDX0 = HIPR1(14)*LOG10(PTJET)/LOG10(5.)
 178                  ELSE
 179                     DEDX0 = HIPR1(14)
 180                  ENDIF
 181                  DP2=DD2*DEDX0/2.0
 182                  DP2=MIN(DP2,PTJET-HIPR1(11))
 183                  PKC2=PTJET-DP2
 184                  DPX2=COS(PHI2)*DP2
 185                  DPY2=SIN(PHI2)*DP2
 186                  PKC21=PT(JT,10)-DPX2
 187                  PKC22=PT(JT,11)-DPY2
 188                  IF(DP2.GT.0.0) THEN
 189                     CTHET=PT(JT,12)/SQRT(PT(JT,12)**2+PTJET**2)
 190                     DPZ2=DP2*CTHET/SQRT(1.0-CTHET**2)
 191                     DPE2=SQRT(DPX2**2+DPY2**2+DPZ2**2)
 192                     ETPPRM=PT(JT,4)+PT(JT,3)-DPE2-DPZ2
 193                     ETMPRM=PT(JT,4)-PT(JT,3)-DPE2+DPZ2
 194                     IF(ETPPRM.LE.0.0.OR.ETMPRM.LE.0.0) GO TO 16
 195                     ETP=ETPPRM
 196                     ETM=ETMPRM
 197                     PT(JT,10)=PKC21
 198                     PT(JT,11)=PKC22
 199                     NTJ(JT)=NTJ(JT)+1
 200                     KFTJ(JT,NTJ(JT))=21
 201                     PJTX(JT,NTJ(JT))=DPX2
 202                     PJTY(JT,NTJ(JT))=DPY2
 203                     PJTZ(JT,NTJ(JT))=DPZ2
 204                     PJTE(JT,NTJ(JT))=DPE2
 205                     PJTM(JT,NTJ(JT))=0.0
 206                     PT(JT,3)=PT(JT,3)-DPZ2
 207                     PT(JT,4)=PT(JT,4)-DPE2
 208                  ENDIF
 209               ENDIF
 210  16           DPKC11=-(PP(JP,10)-PKC11)/2.0
 211               DPKC12=-(PP(JP,11)-PKC12)/2.0
 212               DPKC21=-(PT(JT,10)-PKC21)/2.0
 213               DPKC22=-(PT(JT,11)-PKC22)/2.0
 214               WP=EPP+ETP
 215               WM=EPM+ETM
 216               SW=WP*WM
 217            ENDIF
 218         ENDIF
 219 C               ********If jet is quenched the pt from valence quark
 220 C                       hard scattering has to reduced by d*kapa
 221 C
 222 C
 223 10      PTP02=PP(JP,1)**2+PP(JP,2)**2
 224         PTT02=PT(JT,1)**2+PT(JT,2)**2
 225 C
 226         AMQ=MAX(PP(JP,14)+PP(JP,15),PT(JT,14)+PT(JT,15))
 227         AMX=HIPR1(1)+AMQ
 228 C               ********consider mass cut-off for strings which
 229 C                       must also include quark's mass
 230         AMP0=AMX
 231         DPM0=AMX
 232         NFDP=0
 233         IF(NFP(JP,5).LE.2.AND.NFP(JP,3).NE.0) THEN
 234                 AMP0=ULMASS_HIJING(NFP(JP,3))
 235                 NFDP=NFP(JP,3)+2*NFP(JP,3)/ABS(NFP(JP,3))
 236                 DPM0=ULMASS_HIJING(NFDP)
 237                 IF(DPM0.LE.0.0) THEN
 238                         NFDP=NFDP-2*NFDP/ABS(NFDP)
 239                         DPM0=ULMASS_HIJING(NFDP)
 240                 ENDIF
 241         ENDIF
 242         AMT0=AMX
 243         DTM0=AMX
 244         NFDT=0
 245         IF(NFT(JT,5).LE.2.AND.NFT(JT,3).NE.0) THEN
 246                 AMT0=ULMASS_HIJING(NFT(JT,3))
 247                 NFDT=NFT(JT,3)+2*NFT(JT,3)/ABS(NFT(JT,3))
 248                 DTM0=ULMASS_HIJING(NFDT)
 249                 IF(DTM0.LE.0.0) THEN
 250                         NFDT=NFDT-2*NFDT/ABS(NFDT)
 251                         DTM0=ULMASS_HIJING(NFDT)
 252                 ENDIF
 253         ENDIF
 254 C
 255         AMPN=SQRT(AMP0**2+PTP02)
 256         AMTN=SQRT(AMT0**2+PTT02)
 257         SNN=(AMPN+AMTN)**2+0.001
 258 C
 259         IF(SW.LT.SNN+0.001) GO TO 4000
 260 C               ********Scatter only if SW>SNN
 261 C*****give some PT kick to the two exited strings******************
 262 20      SWPTN=4.0*(MAX(AMP0,AMT0)**2+MAX(PTP02,PTT02))
 263         SWPTD=4.0*(MAX(DPM0,DTM0)**2+MAX(PTP02,PTT02))
 264         SWPTX=4.0*(AMX**2+MAX(PTP02,PTT02))
 265         IF(SW.LE.SWPTN) THEN
 266                 PKCMX=0.0
 267         ELSE IF(SW.GT.SWPTN .AND. SW.LE.SWPTD
 268      &          .AND.NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0) THEN
 269            PKCMX=SQRT(SW/4.0-MAX(AMP0,AMT0)**2)
 270      &           -SQRT(MAX(PTP02,PTT02))
 271         ELSE IF(SW.GT.SWPTD .AND. SW.LE.SWPTX
 272      &          .AND.NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0) THEN
 273            PKCMX=SQRT(SW/4.0-MAX(DPM0,DTM0)**2)
 274      &           -SQRT(MAX(PTP02,PTT02))
 275         ELSE IF(SW.GT.SWPTX) THEN
 276            PKCMX=SQRT(SW/4.0-AMX**2)-SQRT(MAX(PTP02,PTT02))
 277         ENDIF
 278 C               ********maximun PT kick
 279 C*********************************************************
 280 C
 281         IF(NFP(JP,10).EQ.1.OR.NFT(JT,10).EQ.1) THEN
 282                 IF(PKC1.GT.PKCMX) THEN
 283                         PKC1=PKCMX
 284                         PKC11=PKC1*COS(PHI1)
 285                         PKC12=PKC1*SIN(PHI1)
 286                         DPKC11=-(PP(JP,10)-PKC11)/2.0
 287                         DPKC12=-(PP(JP,11)-PKC12)/2.0
 288                 ENDIF
 289                 IF(PKC2.GT.PKCMX) THEN
 290                         PKC2=PKCMX
 291                         PKC21=PKC2*COS(PHI2)
 292                         PKC22=PKC2*SIN(PHI2)
 293                         DPKC21=-(PT(JT,10)-PKC21)/2.0
 294                         DPKC22=-(PT(JT,11)-PKC22)/2.0
 295                 ENDIF
 296                 DPKC1=DPKC11+DPKC21
 297                 DPKC2=DPKC12+DPKC22
 298                 NFP(JP,10)=-NFP(JP,10)
 299                 NFT(JT,10)=-NFT(JT,10)
 300                 GO TO 40
 301         ENDIF
 302 C               ********If the valence quarks had a hard-collision
 303 C                       the pt kick is the pt from hard-collision.
 304         I_SNG=0
 305         IF(IHPR2(13).NE.0 .AND. RLU_HIJING(0).LE.HIDAT(4)) I_SNG=1
 306         IF((NFP(JP,5).EQ.3 .OR.NFT(JT,5).EQ.3).OR.
 307      &          (NPJ(JP).NE.0.OR.NFP(JP,10).NE.0).OR.
 308      &          (NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) I_SNG=0
 309 C
 310 C               ********decite whether to have single-diffractive
 311         IF(IHPR2(5).EQ.0) THEN
 312                 PKC=HIPR1(2)*SQRT(-ALOG(1.0-RLU_HIJING(0)
 313      &                  *(1.0-EXP(-PKCMX**2/HIPR1(2)**2))))
 314                 GO TO 30
 315         ENDIF
 316         PKC=HIRND2(3,0.0,PKCMX**2)
 317         PKC=SQRT(PKC)
 318         IF(PKC.GT.HIPR1(20))
 319      &     PKC=HIPR1(2)*SQRT(-ALOG(EXP(-HIPR1(20)**2/HIPR1(2)**2)
 320      &         -RLU_HIJING(0)*(EXP(-HIPR1(20)**2/HIPR1(2)**2)-
 321      &         EXP(-PKCMX**2/HIPR1(2)**2))))
 322 C
 323         IF(I_SNG.EQ.1) PKC=0.65*SQRT(
 324      &          -ALOG(1.0-RLU_HIJING(0)*(1.0-EXP(-PKCMX**2/0.65**2))))
 325 C                       ********select PT kick
 326 30      PHI0=2.0*HIPR1(40)*RLU_HIJING(0)
 327         PKC11=PKC*SIN(PHI0)
 328         PKC12=PKC*COS(PHI0)
 329         PKC21=-PKC11
 330         PKC22=-PKC12
 331         DPKC1=0.0
 332         DPKC2=0.0
 333 40      PP11=PP(JP,1)+PKC11-DPKC1
 334         PP12=PP(JP,2)+PKC12-DPKC2
 335         PT11=PT(JT,1)+PKC21-DPKC1
 336         PT12=PT(JT,2)+PKC22-DPKC2
 337         PTP2=PP11**2+PP12**2
 338         PTT2=PT11**2+PT12**2
 339 C
 340         AMPN=SQRT(AMP0**2+PTP2)
 341         AMTN=SQRT(AMT0**2+PTT2)
 342         SNN=(AMPN+AMTN)**2+0.001
 343 C***************************************
 344         WP=EPP+ETP
 345         WM=EPM+ETM
 346         SW=WP*WM
 347 C****************************************
 348         IF(SW.LT.SNN) THEN
 349            MISS=MISS+1
 350            IF(MISS.LE.100) then
 351               PKC=0.0
 352               GO TO 30
 353            ENDIF
 354            IF(IHPR2(10).NE.0)
 355      &       WRITE(6,*) 'Error occured in Pt kick section of HIJSFT'
 356            GO TO 4000
 357         ENDIF
 358 C******************************************************************
 359         AMPD=SQRT(DPM0**2+PTP2)
 360         AMTD=SQRT(DTM0**2+PTT2)
 361
 362         AMPX=SQRT(AMX**2+PTP2)
 363         AMTX=SQRT(AMX**2+PTT2)
 364
 365         DPN=AMPN**2/SW
 366         DTN=AMTN**2/SW
 367         DPD=AMPD**2/SW
 368         DTD=AMTD**2/SW
 369         DPX=AMPX**2/SW
 370         DTX=AMTX**2/SW
 371 C
 372         SPNTD=(AMPN+AMTD)**2
 373         SPNTX=(AMPN+AMTX)**2
 374 C                       ********CM energy if proj=N,targ=N*
 375         SPDTN=(AMPD+AMTN)**2
 376         SPXTN=(AMPX+AMTN)**2
 377 C                       ********CM energy if proj=N*,targ=N
 378         SPDTX=(AMPD+AMTX)**2
 379         SPXTD=(AMPX+AMTD)**2
 380         SDD=(AMPD+AMTD)**2
 381         SXX=(AMPX+AMTX)**2
 382
 383 C
 384 C
 385 C               ********CM energy if proj=delta, targ=delta
 386 C****************There are many different cases**********
 387 c       IF(IHPR2(15).EQ.1) GO TO 500
 388 C
 389 C               ********to have DPM type soft interactions
 390 C
 391  45     CONTINUE
 392         IF(SW.GT.SXX+0.001) THEN
 393            IF(I_SNG.EQ.0) THEN
 394               D1=DPX
 395               D2=DTX
 396               NFP3=0
 397               NFT3=0
 398               GO TO 400
 399            ELSE
 400 c**** 5/30/1998 this is identical to the above statement. Added to
 401 c**** avoid questional branching to block.
 402               IF((NFP(JP,5).EQ.3 .AND.NFT(JT,5).EQ.3).OR.
 403      &           (NPJ(JP).NE.0.OR.NFP(JP,10).NE.0).OR.
 404      &           (NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) THEN
 405                  D1=DPX
 406                  D2=DTX
 407                  NFP3=0
 408                  NFT3=0
 409                  GO TO 400
 410               ENDIF
 411 C               ********do not allow excited strings to have
 412 C                       single-diffr
 413               IF(RLU_HIJING(0).GT.0.5.OR.(NFT(JT,5).GT.2.OR.
 414      &                NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) THEN
 415                  D1=DPN
 416                  D2=DTX
 417                  NFP3=NFP(JP,3)
 418                  NFT3=0
 419                  GO TO 220
 420               ELSE
 421                  D1=DPX
 422                  D2=DTN
 423                  NFP3=0
 424                  NFT3=NFT(JT,3)
 425                  GO TO 240
 426               ENDIF
 427 C               ********have single diffractive collision
 428            ENDIF
 429         ELSE IF(SW.GT.MAX(SPDTX,SPXTD)+0.001 .AND.
 430      &                          SW.LE.SXX+0.001) THEN
 431            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0.AND.
 432      &         RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 433      &         .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 434               D1=DPD
 435               D2=DTX
 436               NFP3=NFDP
 437               NFT3=0
 438               GO TO 220
 439            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 440               D1=DPX
 441               D2=DTD
 442               NFP3=0
 443               NFT3=NFDT
 444               GO TO 240
 445            ENDIF
 446            GO TO 4000
 447         ELSE IF(SW.GT.MIN(SPDTX,SPXTD)+0.001.AND.
 448      &                  SW.LE.MAX(SPDTX,SPXTD)+0.001) THEN
 449            IF(SPDTX.LE.SPXTD.AND.NPJ(JP).EQ.0
 450      &                       .AND.NFP(JP,5).LE.2) THEN
 451               D1=DPD
 452               D2=DTX
 453               NFP3=NFDP
 454               NFT3=0
 455               GO TO 220
 456            ELSE IF(SPDTX.GT.SPXTD.AND.NTJ(JT).EQ.0
 457      &                       .AND.NFT(JT,5).LE.2) THEN
 458               D1=DPX
 459               D2=DTD
 460               NFP3=0
 461               NFT3=NFDT
 462               GO TO 240
 463            ENDIF
 464 c*** 5/30/1998 added to avoid questional branching to another block
 465 c*** this is identical to the statement following the next ELSE IF
 466            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0
 467      &       .AND.RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 468      &        .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 469               D1=DPN
 470               D2=DTX
 471               NFP3=NFP(JP,3)
 472               NFT3=0
 473               GO TO 220
 474            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 475               D1=DPX
 476               D2=DTN
 477               NFP3=0
 478               NFT3=NFT(JT,3)
 479               GO TO 240
 480            ENDIF
 481            GO TO 4000
 482         ELSE IF(SW.GT.MAX(SPNTX,SPXTN)+0.001 .AND.
 483      &                  SW.LE.MIN(SPDTX,SPXTD)+0.001) THEN
 484            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0
 485      &       .AND.RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 486      &        .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 487               D1=DPN
 488               D2=DTX
 489               NFP3=NFP(JP,3)
 490               NFT3=0
 491               GO TO 220
 492            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 493               D1=DPX
 494               D2=DTN
 495               NFP3=0
 496               NFT3=NFT(JT,3)
 497               GO TO 240
 498            ENDIF
 499            GO TO 4000
 500         ELSE IF(SW.GT.MIN(SPNTX,SPXTN)+0.001 .AND.
 501      &                  SW.LE.MAX(SPNTX,SPXTN)+0.001) THEN
 502            IF(SPNTX.LE.SPXTN.AND.NPJ(JP).EQ.0
 503      &                           .AND.NFP(JP,5).LE.2) THEN
 504               D1=DPN
 505               D2=DTX
 506               NFP3=NFP(JP,3)
 507               NFT3=0
 508               GO TO 220
 509            ELSEIF(SPNTX.GT.SPXTN.AND.NTJ(JT).EQ.0
 510      &                           .AND.NFT(JT,5).LE.2) THEN
 511               D1=DPX
 512               D2=DTN
 513               NFP3=0
 514               NFT3=NFT(JT,3)
 515               GO TO 240
 516            ENDIF
 517            GO TO 4000
 518         ELSE IF(SW.LE.MIN(SPNTX,SPXTN)+0.001 .AND.
 519      &                  (NPJ(JP).NE.0 .OR.NTJ(JT).NE.0)) THEN
 520            GO TO 4000
 521         ELSE IF(SW.LE.MIN(SPNTX,SPXTN)+0.001 .AND.
 522      &          NFP(JP,5).GT.2.AND.NFT(JT,5).GT.2) THEN
 523            GO TO 4000
 524         ELSE IF(SW.GT.SDD+0.001.AND.SW.LE.
 525      &                     MIN(SPNTX,SPXTN)+0.001) THEN
 526            D1=DPD
 527            D2=DTD
 528            NFP3=NFDP
 529            NFT3=NFDT
 530            GO TO 100
 531         ELSE IF(SW.GT.MAX(SPNTD,SPDTN)+0.001
 532      &                      .AND. SW.LE.SDD+0.001) THEN
 533            IF(RLU_HIJING(0).GT.0.5) THEN
 534               D1=DPD
 535               D2=DTN
 536               NFP3=NFDP
 537               NFT3=NFT(JT,3)
 538               GO TO 100
 539            ELSE
 540               D1=DPN
 541               D2=DTD
 542               NFP3=NFP(JP,3)
 543               NFT3=NFDT
 544               GO TO 100
 545            ENDIF
 546         ELSE IF(SW.GT.MIN(SPNTD,SPDTN)+0.001
 547      &          .AND. SW.LE.MAX(SPNTD,SPDTN)+0.001) THEN
 548            IF(SPNTD.GT.SPDTN) THEN
 549               D1=DPD
 550               D2=DTN
 551               NFP3=NFDP
 552               NFT3=NFT(JT,3)
 553               GO TO 100
 554            ELSE
 555               D1=DPN
 556               D2=DTD
 557               NFP3=NFP(JP,3)
 558               NFT3=NFDT
 559               GO TO 100
 560            ENDIF
 561         ELSE IF(SW.LE.MIN(SPNTD,SPDTN)+0.001) THEN
 562            D1=DPN
 563            D2=DTN
 564            NFP3=NFP(JP,3)
 565            NFT3=NFT(JT,3)
 566            GO TO 100
 567         ENDIF
 568         WRITE(6,*) ' Error in HIJSFT: There is no path to here'
 569         RETURN
 570 C
 571 C***************  elastic scattering ***************
 572 C       this is like elastic, both proj and targ mass
 573 C       must be fixed
 574 C***************************************************
 575 100     NFP5=MAX(2,NFP(JP,5))
 576         NFT5=MAX(2,NFT(JT,5))
 577         BB1=1.0+D1-D2
 578         BB2=1.0+D2-D1
 579         IF(BB1**2.LT.4.0*D1 .OR. BB2**2.LT.4.0*D2) THEN
 580                 MISS=MISS+1
 581                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 582                 PKC=PKC*0.5
 583                 GO TO 30
 584         ENDIF
 585         IF(RLU_HIJING(0).LT.0.5) THEN
 586                 X1=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 587                 X2=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 588         ELSE
 589                 X1=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 590                 X2=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 591         ENDIF
 592         IHNT2(13)=2
 593         GO TO 600
 594 C
 595 C********** Single diffractive ***********************
 596 C either proj or targ's mass is fixed
 597 C*****************************************************
 598 220     NFP5=MAX(2,NFP(JP,5))
 599         NFT5=3
 600         IF(NFP3.EQ.0) NFP5=3
 601         BB2=1.0+D2-D1
 602         IF(BB2**2.LT.4.0*D2) THEN
 603                 MISS=MISS+1
 604                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 605                 PKC=PKC*0.5
 606                 GO TO 30
 607         ENDIF
 608         XMIN=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 609         XMAX=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 610         MISS4=0
 611 222     X2=HIRND2(6,XMIN,XMAX)
 612         X1=D1/(1.0-X2)
 613         IF(X2*(1.0-X1).LT.(D2+1.E-4/SW)) THEN
 614                 MISS4=MISS4+1
 615                 IF(MISS4.LE.1000) GO TO 222
 616                 GO TO 5000
 617         ENDIF
 618         IHNT2(13)=2
 619         GO TO 600
 620 C                       ********Fix proj mass*********
 621 240     NFP5=3
 622         NFT5=MAX(2,NFT(JT,5))
 623         IF(NFT3.EQ.0) NFT5=3
 624         BB1=1.0+D1-D2
 625         IF(BB1**2.LT.4.0*D1) THEN
 626                 MISS=MISS+1
 627                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 628                 PKC=PKC*0.5
 629                 GO TO 30
 630         ENDIF
 631         XMIN=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 632         XMAX=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 633         MISS4=0
 634 242     X1=HIRND2(6,XMIN,XMAX)
 635         X2=D2/(1.0-X1)
 636         IF(X1*(1.0-X2).LT.(D1+1.E-4/SW)) THEN
 637                 MISS4=MISS4+1
 638                 IF(MISS4.LE.1000) GO TO 242
 639                 GO TO 5000
 640         ENDIF
 641         IHNT2(13)=2
 642         GO TO 600
 643 C                       ********Fix targ mass*********
 644 C
 645 C*************non-single diffractive**********************
 646 C       both proj and targ may not be fixed in mass
 647 C*********************************************************
 648 C
 649 400     NFP5=3
 650         NFT5=3
 651         BB1=1.0+D1-D2
 652         BB2=1.0+D2-D1
 653         IF(BB1**2.LT.4.0*D1 .OR. BB2**2.LT.4.0*D2) THEN
 654                 MISS=MISS+1
 655                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 656                 PKC=PKC*0.5
 657                 GO TO 30
 658         ENDIF
 659         XMIN1=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 660         XMAX1=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 661         XMIN2=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 662         XMAX2=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 663         MISS4=0
 664 410     X1=HIRND2(4,XMIN1,XMAX1)
 665         X2=HIRND2(4,XMIN2,XMAX2)
 666         IF(NFP(JP,5).EQ.3.OR.NFT(JT,5).EQ.3) THEN
 667                 X1=HIRND2(6,XMIN1,XMAX1)
 668                 X2=HIRND2(6,XMIN2,XMAX2)
 669         ENDIF
 670 C                       ********
 671         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000.OR.
 672      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.100) THEN
 673                 X1=HIRND2(5,XMIN1,XMAX1)
 674         ENDIF
 675         IF(ABS(NFT(JT,1)*NFT(JT,2)).GT.1000000.OR.
 676      &                  ABS(NFT(JT,1)*NFT(JT,2)).LT.100) THEN
 677                 X2=HIRND2(5,XMIN2,XMAX2)
 678         ENDIF
 679 c       IF(IOPMAIN.EQ.3) X1=HIRND2(6,XMIN1,XMAX1)
 680 c       IF(IOPMAIN.EQ.2) X2=HIRND2(6,XMIN2,XMAX2)
 681 C       ********For q-qbar or (qq)-(qq)bar system use symetric
 682 C               distribution, for q-(qq) or qbar-(qq)bar use
 683 C               unsymetrical distribution
 684 C
 685         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000) X1=1.0-X1
 686         XXP=X1*(1.0-X2)
 687         XXT=X2*(1.0-X1)
 688         IF(XXP.LT.(D1+1.E-4/SW) .OR. XXT.LT.(D2+1.E-4/SW)) THEN
 689                 MISS4=MISS4+1
 690                 IF(MISS4.LE.1000) GO TO 410
 691                 GO TO 5000
 692         ENDIF
 693         IHNT2(13)=3
 694 C***************************************************
 695 C***************************************************
 696 600     CONTINUE
 697         IF(X1*(1.0-X2).LT.(AMPN**2-1.E-4)/SW.OR.
 698      &                  X2*(1.0-X1).LT.(AMTN**2-1.E-4)/SW) THEN
 699                 MISS=MISS+1
 700                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 2000
 701                 PKC=0.0
 702                 GO TO 30
 703         ENDIF
 704 C
 705         EPP=(1.0-X2)*WP
 706         EPM=X1*WM
 707         ETP=X2*WP
 708         ETM=(1.0-X1)*WM
 709         PP(JP,3)=(EPP-EPM)/2.0
 710         PP(JP,4)=(EPP+EPM)/2.0
 711         IF(EPP*EPM-PTP2.LT.0.0) GO TO 6000
 712         PP(JP,5)=SQRT(EPP*EPM-PTP2)
 713         NFP(JP,3)=NFP3
 714         NFP(JP,5)=NFP5
 715
 716         PT(JT,3)=(ETP-ETM)/2.0
 717         PT(JT,4)=(ETP+ETM)/2.0
 718         IF(ETP*ETM-PTT2.LT.0.0) GO TO 6000
 719         PT(JT,5)=SQRT(ETP*ETM-PTT2)
 720         NFT(JT,3)=NFT3
 721         NFT(JT,5)=NFT5
 722 C*****recoil PT from hard-inter is shared by two end-partons
 723 C       so that pt=p1+p2
 724         PP(JP,1)=PP11-PKC11
 725         PP(JP,2)=PP12-PKC12
 726
 727         KICKDIP=1
 728         KICKDIT=1
 729         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000.OR.
 730      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.100) THEN
 731                 KICKDIP=0
 732         ENDIF
 733         IF(ABS(NFT(JT,1)*NFT(JT,2)).GT.1000000.OR.
 734      &                  ABS(NFT(JT,1)*NFT(JT,2)).LT.100) THEN
 735                 KICKDIT=0
 736         ENDIF
 737         IF((KICKDIP.EQ.0.AND.RLU_HIJING(0).LT.0.5)
 738      &     .OR.(KICKDIP.NE.0.AND.RLU_HIJING(0)
 739      &     .LT.0.5/(1.0+(PKC11**2+PKC12**2)/HIPR1(22)**2))) THEN
 740            PP(JP,6)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0+PP(JP,6)
 741            PP(JP,7)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0+PP(JP,7)
 742            PP(JP,8)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0
 743      &              +PP(JP,8)+PKC11
 744            PP(JP,9)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0
 745      &              +PP(JP,9)+PKC12
 746         ELSE
 747            PP(JP,8)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0+PP(JP,8)
 748            PP(JP,9)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0+PP(JP,9)
 749            PP(JP,6)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0
 750      &              +PP(JP,6)+PKC11
 751            PP(JP,7)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0
 752      &              +PP(JP,7)+PKC12
 753         ENDIF
 754         PP(JP,1)=PP(JP,6)+PP(JP,8)
 755         PP(JP,2)=PP(JP,7)+PP(JP,9)
 756 C                               ********pt kick for proj
 757         PT(JT,1)=PT11-PKC21
 758         PT(JT,2)=PT12-PKC22
 759         IF((KICKDIT.EQ.0.AND.RLU_HIJING(0).LT.0.5)
 760      &     .OR.(KICKDIT.NE.0.AND.RLU_HIJING(0)
 761      &     .LT.0.5/(1.0+(PKC21**2+PKC22**2)/HIPR1(22)**2))) THEN
 762            PT(JT,6)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0+PT(JT,6)
 763            PT(JT,7)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0+PT(JT,7)
 764            PT(JT,8)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0
 765      &              +PT(JT,8)+PKC21
 766            PT(JT,9)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0
 767      &              +PT(JT,9)+PKC22
 768         ELSE
 769            PT(JT,8)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0+PT(JT,8)
 770            PT(JT,9)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0+PT(JT,9)
 771            PT(JT,6)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0
 772      &              +PT(JT,6)+PKC21
 773            PT(JT,7)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0
 774      &              +PT(JT,7)+PKC22
 775         ENDIF
 776         PT(JT,1)=PT(JT,6)+PT(JT,8)
 777         PT(JT,2)=PT(JT,7)+PT(JT,9)
 778 C                       ********pt kick for targ
 779
 780         IF(NPJ(JP).NE.0) NFP(JP,5)=3
 781         IF(NTJ(JT).NE.0) NFT(JT,5)=3
 782 C                       ********jets must be connected to string
 783         IF(EPP/(EPM+0.0001).LT.ETP/(ETM+0.0001).AND.
 784      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.1000000)THEN
 785                 DO 620 JSB=1,15
 786                 PSB=PP(JP,JSB)
 787                 PP(JP,JSB)=PT(JT,JSB)
 788                 PT(JT,JSB)=PSB
 789                 NSB=NFP(JP,JSB)
 790                 NFP(JP,JSB)=NFT(JT,JSB)
 791                 NFT(JT,JSB)=NSB
 792 620             CONTINUE
 793 C               ********when Ycm(JP)<Ycm(JT) after the collision
 794 C                       exchange the positions of the two
 795         ENDIF
 796 C
 797         RETURN
 798 C**************************************************
 799 C**************************************************
 800 1000    IERROR=1
 801         IF(IHPR2(10).EQ.0) RETURN
 802         WRITE(6,*) '    Fatal HIJSFT start error,abandon this event'
 803         WRITE(6,*) '    PROJ E+,E-,W+',EPP,EPM,WP
 804         WRITE(6,*) '    TARG E+,E-,W-',ETP,ETM,WM
 805         WRITE(6,*) '    W+*W-, (APN+ATN)^2',SW,SNN
 806         RETURN
 807 2000    IERROR=0
 808         IF(IHPR2(10).EQ.0) RETURN
 809         WRITE(6,*) '    (2)energy partition fail,'
 810         WRITE(6,*) '    HIJSFT not performed, but continue'
 811         WRITE(6,*) '    MP1,MPN',X1*(1.0-X2)*SW,AMPN**2
 812         WRITE(6,*) '    MT2,MTN',X2*(1.0-X1)*SW,AMTN**2
 813         RETURN
 814 3000    IERROR=0
 815         IF(IHPR2(10).EQ.0) RETURN
 816         WRITE(6,*) '    (3)something is wrong with the pt kick, '
 817         WRITE(6,*) '    HIJSFT not performed, but continue'
 818         WRITE(6,*) '    D1=',D1,' D2=',D2,' SW=',SW
 819         WRITE(6,*) '    HISTORY NFP5=',NFP(JP,5),' NFT5=',NFT(JT,5)
 820         WRITE(6,*) '    THIS COLLISON NFP5=',NFP5, ' NFT5=',NFT5
 821         WRITE(6,*) '    # OF JET IN PROJ',NPJ(JP),' IN TARG',NTJ(JT)
 822         RETURN
 823 4000    IERROR=0
 824         IF(IHPR2(10).EQ.0) RETURN
 825         WRITE(6,*) '    (4)unable to choose process, but not harmful'
 826         WRITE(6,*) '    HIJSFT not performed, but continue'
 827         WRITE(6,*) '    PTP=',SQRT(PTP2),' PTT=',SQRT(PTT2),' SW=',SW
 828         WRITE(6,*) '    AMCUT=',AMX,' JP=',JP,' JT=',JT
 829         WRITE(6,*) '    HISTORY NFP5=',NFP(JP,5),' NFT5=',NFT(JT,5)
 830         RETURN
 831 5000    IERROR=0
 832         IF(IHPR2(10).EQ.0) RETURN
 833         WRITE(6,*) '    energy partition failed(5),for limited try'
 834         WRITE(6,*) '    HIJSFT not performed, but continue'
 835         WRITE(6,*) '    NFP5=',NFP5,' NFT5=',NFT5
 836         WRITE(6,*) '    D1',D1,' X1(1-X2)',X1*(1.0-X2)
 837         WRITE(6,*) '    D2',D2,' X2(1-X1)',X2*(1.0-X1)
 838         RETURN
 839 6000    PKC=0.0
 840         MISS=MISS+1
 841         IF(MISS.LT.100) GO TO 30
 842         IERROR=1
 843         IF(IHPR2(10).EQ.0) RETURN
 844         WRITE(6,*) ' ERROR OCCURED, HIJSFT NOT PERFORMED'
 845         WRITE(6,*) ' Abort this event'
 846         WRITE(6,*) 'MTP,PTP2',EPP*EPM,PTP2,'  MTT,PTT2',ETP*ETM,PTT2
 847         RETURN
 848         END