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 C
  89 C Quenching requested ?
  90 C
  91            IF(IHPR2(4).GT.0.AND.IHNT2(1).GT.1.AND.IHNT2(3).GT.1) THEN
  92               IF(NFP(JP,10).EQ.0) THEN
  93                  PHI=-PHI2
  94               ELSE IF(NFT(JT,10).EQ.0) THEN
  95                  PHI=PHI1
  96               ELSE
  97                  IF (PHI1.LT.0. .AND. PHI2.GT.0) THEN ! PH AM
  98                     PHI=(PHI1+PHI2-HIPR1(40))/2.0     ! PH AM
  99                  ELSE                                 ! PH AM
 100                     PHI=(PHI1+PHI2+HIPR1(40))/2.0     ! PH AM
 101                  ENDIF                                ! PH AM
 102               ENDIF
 103               BX=HINT1(19)*COS(HINT1(20))
 104               BY=HINT1(19)*SIN(HINT1(20))
 105               XP0=YP(1,JP)
 106               YP0=YP(2,JP)
 107               XT0=YT(1,JT)+BX
 108               YT0=YT(2,JT)+BY
 109               R1=MAX(1.2*IHNT2(1)**0.3333333,
 110      &               SQRT(XP0**2+YP0**2))
 111               R2=MAX(1.2*IHNT2(3)**0.3333333,
 112      &               SQRT((XT0-BX)**2+(YT0-BY)**2))
 113               IF(ABS(COS(PHI)).LT.1.0E-5) THEN
 114 C AM             DD1=R1
 115 C AM             DD2=R1
 116                  DD1 = ABS(SQRT(R1**2-(XT0-BX)**2) - YT0)
 117                  DD2 = ABS(SQRT(R1**2-(XT0-BX)**2) + YT0)
 118 C PH             DD3=ABS(BY+SQRT(R2**2-(XP0-BX)**2)-YP0)
 119 C PH             DD4=ABS(BY-SQRT(R2**2-(XP0-BX)**2)-YP0)
 120                  DD3=ABS(BY+SQRT(R2**2-(XT0-BX)**2)-YP0)
 121                  DD4=ABS(BY-SQRT(R2**2-(XT0-BX)**2)-YP0)
 122                  GO TO 5
 123               ENDIF
 124               BB=2.0*SIN(PHI)*(COS(PHI)*YP0-SIN(PHI)*XP0)
 125               CC=(YP0**2-R1**2)*COS(PHI)**2+XP0*SIN(PHI)*(
 126      &                          XP0*SIN(PHI)-2.0*YP0*COS(PHI))
 127               DD=BB**2-4.0*CC
 128               IF(DD.LT.0.0) GO TO 10
 129               XX1=(-BB+SQRT(DD))/2.0
 130               XX2=(-BB-SQRT(DD))/2.0
 131               DD1=ABS((XX1-XP0)/COS(PHI))
 132               DD2=ABS((XX2-XP0)/COS(PHI))
 133 C
 134               BB=2.0*SIN(PHI)*(COS(PHI)*(YT0-BY)-SIN(PHI)*XT0)-2.0*BX
 135               CC=(BX**2+(YT0-BY)**2-R2**2)*COS(PHI)**2+XT0*SIN(PHI)
 136      &           *(XT0*SIN(PHI)-2.0*COS(PHI)*(YT0-BY))
 137      &           -2.0*BX*SIN(PHI)*(COS(PHI)*(YT0-BY)-SIN(PHI)*XT0)
 138               DD=BB**2-4.0*CC
 139               IF(DD.LT.0.0) GO TO 10
 140               XX1=(-BB+SQRT(DD))/2.0
 141               XX2=(-BB-SQRT(DD))/2.0
 142               DD3=ABS((XX1-XT0)/COS(PHI))
 143               DD4=ABS((XX2-XT0)/COS(PHI))
 144 C
 145  5            DD1=MIN(DD1,DD3)
 146               DD2=MIN(DD2,DD4)
 147               IF(DD1.LT.HIPR1(13)) DD1=0.0
 148               IF(DD2.LT.HIPR1(13)) DD2=0.0
 149               IF(NFP(JP,10).EQ.1.AND.PPJET.GT.HIPR1(11)) THEN
 150                  IF (IHPR2(50) .EQ. 1) THEN
 151                     DEDX0 = HIPR1(14)*LOG10(PPJET)/LOG10(5.)
 152                  ELSE
 153                     DEDX0 = HIPR1(14)
 154                  ENDIF
 155                  DP1=DD1*DEDX0/2.0
 156                  DP1=MIN(DP1,PPJET-HIPR1(11))
 157                  PKC1=PPJET-DP1
 158                  DPX1=COS(PHI1)*DP1
 159                  DPY1=SIN(PHI1)*DP1
 160                  PKC11=PP(JP,10)-DPX1
 161                  PKC12=PP(JP,11)-DPY1
 162                  IF(DP1.GT.0.0) THEN
 163                     CTHEP=PP(JP,12)/SQRT(PP(JP,12)**2+PPJET**2)
 164                     DPZ1=DP1*CTHEP/SQRT(1.0-CTHEP**2)
 165                     DPE1=SQRT(DPX1**2+DPY1**2+DPZ1**2)
 166                     EPPPRM=PP(JP,4)+PP(JP,3)-DPE1-DPZ1
 167                     EPMPRM=PP(JP,4)-PP(JP,3)-DPE1+DPZ1
 168                     IF(EPPPRM.LE.0.0.OR.EPMPRM.LE.0.0) GO TO 15
 169                     EPP=EPPPRM
 170                     EPM=EPMPRM
 171                     PP(JP,10)=PKC11
 172                     PP(JP,11)=PKC12
 173                     NPJ(JP)=NPJ(JP)+1
 174                     KFPJ(JP,NPJ(JP))=21
 175                     PJPX(JP,NPJ(JP))=DPX1
 176                     PJPY(JP,NPJ(JP))=DPY1
 177                     PJPZ(JP,NPJ(JP))=DPZ1
 178                     PJPE(JP,NPJ(JP))=DPE1
 179                     PJPM(JP,NPJ(JP))=0.0
 180                     PP(JP,3)=PP(JP,3)-DPZ1
 181                     PP(JP,4)=PP(JP,4)-DPE1
 182                  ENDIF
 183               ENDIF
 184  15           IF(NFT(JT,10).EQ.1.AND.PTJET.GT.HIPR1(11)) THEN
 185                  IF (IHPR2(50) .EQ. 1) THEN
 186                     DEDX0 = HIPR1(14)*LOG10(PTJET)/LOG10(5.)
 187                  ELSE
 188                     DEDX0 = HIPR1(14)
 189                  ENDIF
 190                  DP2=DD2*DEDX0/2.0
 191                  DP2=MIN(DP2,PTJET-HIPR1(11))
 192                  PKC2=PTJET-DP2
 193                  DPX2=COS(PHI2)*DP2
 194                  DPY2=SIN(PHI2)*DP2
 195                  PKC21=PT(JT,10)-DPX2
 196                  PKC22=PT(JT,11)-DPY2
 197                  IF(DP2.GT.0.0) THEN
 198                     CTHET=PT(JT,12)/SQRT(PT(JT,12)**2+PTJET**2)
 199                     DPZ2=DP2*CTHET/SQRT(1.0-CTHET**2)
 200                     DPE2=SQRT(DPX2**2+DPY2**2+DPZ2**2)
 201                     ETPPRM=PT(JT,4)+PT(JT,3)-DPE2-DPZ2
 202                     ETMPRM=PT(JT,4)-PT(JT,3)-DPE2+DPZ2
 203                     IF(ETPPRM.LE.0.0.OR.ETMPRM.LE.0.0) GO TO 16
 204                     ETP=ETPPRM
 205                     ETM=ETMPRM
 206                     PT(JT,10)=PKC21
 207                     PT(JT,11)=PKC22
 208                     NTJ(JT)=NTJ(JT)+1
 209                     KFTJ(JT,NTJ(JT))=21
 210                     PJTX(JT,NTJ(JT))=DPX2
 211                     PJTY(JT,NTJ(JT))=DPY2
 212                     PJTZ(JT,NTJ(JT))=DPZ2
 213                     PJTE(JT,NTJ(JT))=DPE2
 214                     PJTM(JT,NTJ(JT))=0.0
 215                     PT(JT,3)=PT(JT,3)-DPZ2
 216                     PT(JT,4)=PT(JT,4)-DPE2
 217                  ENDIF
 218               ENDIF
 219  16           CONTINUE
 220               PKC11=0.
 221               PKC12=0.
 222               PKC21=0.
 223               PKC22=0.
 224               DPKC11=0.
 225               DPKC12=0.
 226               DPKC21=0.
 227               DPKC22=0.
 228
 229               WP=EPP+ETP
 230               WM=EPM+ETM
 231               SW=WP*WM
 232            ENDIF
 233         ENDIF
 234
 235         IF(NFP(JP,10).EQ.1) THEN
 236            PPJET=SQRT(PP(JP,10)**2+PP(JP,11)**2)
 237            PKC1=PPJET
 238         ENDIF
 239         IF(NFT(JT,10).EQ.1) THEN
 240            PTJET=SQRT(PT(JT,10)**2+PT(JT,11)**2)
 241            PKC2=PTJET
 242         ENDIF
 243 C               ********If jet is quenched the pt from valence quark
 244 C                       hard scattering has to reduced by d*kapa
 245 C
 246 C
 247 10      PTP02=PP(JP,1)**2+PP(JP,2)**2
 248         PTT02=PT(JT,1)**2+PT(JT,2)**2
 249 C
 250         AMQ=MAX(PP(JP,14)+PP(JP,15),PT(JT,14)+PT(JT,15))
 251         AMX=HIPR1(1)+AMQ
 252 C               ********consider mass cut-off for strings which
 253 C                       must also include quark's mass
 254         AMP0=AMX
 255         DPM0=AMX
 256         NFDP=0
 257         IF(NFP(JP,5).LE.2.AND.NFP(JP,3).NE.0) THEN
 258                 AMP0=ULMASS_HIJING(NFP(JP,3))
 259                 NFDP=NFP(JP,3)+2*NFP(JP,3)/ABS(NFP(JP,3))
 260                 DPM0=ULMASS_HIJING(NFDP)
 261                 IF(DPM0.LE.0.0) THEN
 262                         NFDP=NFDP-2*NFDP/ABS(NFDP)
 263                         DPM0=ULMASS_HIJING(NFDP)
 264                 ENDIF
 265         ENDIF
 266         AMT0=AMX
 267         DTM0=AMX
 268         NFDT=0
 269         IF(NFT(JT,5).LE.2.AND.NFT(JT,3).NE.0) THEN
 270                 AMT0=ULMASS_HIJING(NFT(JT,3))
 271                 NFDT=NFT(JT,3)+2*NFT(JT,3)/ABS(NFT(JT,3))
 272                 DTM0=ULMASS_HIJING(NFDT)
 273                 IF(DTM0.LE.0.0) THEN
 274                         NFDT=NFDT-2*NFDT/ABS(NFDT)
 275                         DTM0=ULMASS_HIJING(NFDT)
 276                 ENDIF
 277         ENDIF
 278 C
 279         AMPN=SQRT(AMP0**2+PTP02)
 280         AMTN=SQRT(AMT0**2+PTT02)
 281         SNN=(AMPN+AMTN)**2+0.001
 282 C
 283         IF(SW.LT.SNN+0.001) GO TO 4000
 284 C               ********Scatter only if SW>SNN
 285 C*****give some PT kick to the two exited strings******************
 286 20      SWPTN=4.0*(MAX(AMP0,AMT0)**2+MAX(PTP02,PTT02))
 287         SWPTD=4.0*(MAX(DPM0,DTM0)**2+MAX(PTP02,PTT02))
 288         SWPTX=4.0*(AMX**2+MAX(PTP02,PTT02))
 289         IF(SW.LE.SWPTN) THEN
 290                 PKCMX=0.0
 291         ELSE IF(SW.GT.SWPTN .AND. SW.LE.SWPTD
 292      &          .AND.NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0) THEN
 293            PKCMX=SQRT(SW/4.0-MAX(AMP0,AMT0)**2)
 294      &           -SQRT(MAX(PTP02,PTT02))
 295         ELSE IF(SW.GT.SWPTD .AND. SW.LE.SWPTX
 296      &          .AND.NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0) THEN
 297            PKCMX=SQRT(SW/4.0-MAX(DPM0,DTM0)**2)
 298      &           -SQRT(MAX(PTP02,PTT02))
 299         ELSE IF(SW.GT.SWPTX) THEN
 300            PKCMX=SQRT(SW/4.0-AMX**2)-SQRT(MAX(PTP02,PTT02))
 301         ENDIF
 302 C               ********maximun PT kick
 303 C*********************************************************
 304         IF(NFP(JP,10).EQ.1.OR.NFT(JT,10).EQ.1) THEN
 305                 IF(PKC1.GT.PKCMX) THEN
 306                         PKC1=PKCMX
 307                         PKC11=PKC1*COS(PHI1)
 308                         PKC12=PKC1*SIN(PHI1)
 309                         DPKC11=-(PP(JP,10)-PKC11)/2.0
 310                         DPKC12=-(PP(JP,11)-PKC12)/2.0
 311                 ENDIF
 312                 IF(PKC2.GT.PKCMX) THEN
 313                         PKC2=PKCMX
 314                         PKC21=PKC2*COS(PHI2)
 315                         PKC22=PKC2*SIN(PHI2)
 316                         DPKC21=-(PT(JT,10)-PKC21)/2.0
 317                         DPKC22=-(PT(JT,11)-PKC22)/2.0
 318                 ENDIF
 319                 DPKC1=DPKC11+DPKC21
 320                 DPKC2=DPKC12+DPKC22
 321                 NFP(JP,10)=-NFP(JP,10)
 322                 NFT(JT,10)=-NFT(JT,10)
 323                 GO TO 40
 324         ENDIF
 325 C               ********If the valence quarks had a hard-collision
 326 C                       the pt kick is the pt from hard-collision.
 327         I_SNG=0
 328         IF(IHPR2(13).NE.0 .AND. RLU_HIJING(0).LE.HIDAT(4)) I_SNG=1
 329         IF((NFP(JP,5).EQ.3 .OR.NFT(JT,5).EQ.3).OR.
 330      &          (NPJ(JP).NE.0.OR.NFP(JP,10).NE.0).OR.
 331      &          (NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) I_SNG=0
 332 C
 333 C               ********decite whether to have single-diffractive
 334         IF(IHPR2(5).EQ.0) THEN
 335                 PKC=HIPR1(2)*SQRT(-ALOG(1.0-RLU_HIJING(0)
 336      &                  *(1.0-EXP(-PKCMX**2/HIPR1(2)**2))))
 337                 GO TO 30
 338         ENDIF
 339         PKC=HIRND2(3,0.0,PKCMX**2)
 340         PKC=SQRT(PKC)
 341         IF(PKC.GT.HIPR1(20))
 342      &     PKC=HIPR1(2)*SQRT(-ALOG(EXP(-HIPR1(20)**2/HIPR1(2)**2)
 343      &         -RLU_HIJING(0)*(EXP(-HIPR1(20)**2/HIPR1(2)**2)-
 344      &         EXP(-PKCMX**2/HIPR1(2)**2))))
 345 C
 346         IF(I_SNG.EQ.1) PKC=0.65*SQRT(
 347      &          -ALOG(1.0-RLU_HIJING(0)*(1.0-EXP(-PKCMX**2/0.65**2))))
 348 C                       ********select PT kick
 349 30      PHI0=2.0*HIPR1(40)*RLU_HIJING(0)
 350         PKC11=PKC*SIN(PHI0)
 351         PKC12=PKC*COS(PHI0)
 352         PKC21=-PKC11
 353         PKC22=-PKC12
 354         DPKC1=0.0
 355         DPKC2=0.0
 356 40      PP11=PP(JP,1)+PKC11-DPKC1
 357         PP12=PP(JP,2)+PKC12-DPKC2
 358         PT11=PT(JT,1)+PKC21-DPKC1
 359         PT12=PT(JT,2)+PKC22-DPKC2
 360         PTP2=PP11**2+PP12**2
 361         PTT2=PT11**2+PT12**2
 362 C
 363         AMPN=SQRT(AMP0**2+PTP2)
 364         AMTN=SQRT(AMT0**2+PTT2)
 365         SNN=(AMPN+AMTN)**2+0.001
 366 C***************************************
 367         WP=EPP+ETP
 368         WM=EPM+ETM
 369         SW=WP*WM
 370 C****************************************
 371         IF(SW.LT.SNN) THEN
 372            MISS=MISS+1
 373            IF(MISS.LE.100) then
 374               PKC=0.0
 375               GO TO 30
 376            ENDIF
 377            IF(IHPR2(10).NE.0)
 378      &       WRITE(6,*) 'Error occured in Pt kick section of HIJSFT'
 379            GO TO 4000
 380         ENDIF
 381 C******************************************************************
 382         AMPD=SQRT(DPM0**2+PTP2)
 383         AMTD=SQRT(DTM0**2+PTT2)
 384
 385         AMPX=SQRT(AMX**2+PTP2)
 386         AMTX=SQRT(AMX**2+PTT2)
 387
 388         DPN=AMPN**2/SW
 389         DTN=AMTN**2/SW
 390         DPD=AMPD**2/SW
 391         DTD=AMTD**2/SW
 392         DPX=AMPX**2/SW
 393         DTX=AMTX**2/SW
 394 C
 395         SPNTD=(AMPN+AMTD)**2
 396         SPNTX=(AMPN+AMTX)**2
 397 C                       ********CM energy if proj=N,targ=N*
 398         SPDTN=(AMPD+AMTN)**2
 399         SPXTN=(AMPX+AMTN)**2
 400 C                       ********CM energy if proj=N*,targ=N
 401         SPDTX=(AMPD+AMTX)**2
 402         SPXTD=(AMPX+AMTD)**2
 403         SDD=(AMPD+AMTD)**2
 404         SXX=(AMPX+AMTX)**2
 405
 406 C
 407 C
 408 C               ********CM energy if proj=delta, targ=delta
 409 C****************There are many different cases**********
 410 c       IF(IHPR2(15).EQ.1) GO TO 500
 411 C
 412 C               ********to have DPM type soft interactions
 413 C
 414  45     CONTINUE
 415         IF(SW.GT.SXX+0.001) THEN
 416            IF(I_SNG.EQ.0) THEN
 417               D1=DPX
 418               D2=DTX
 419               NFP3=0
 420               NFT3=0
 421               GO TO 400
 422            ELSE
 423 c**** 5/30/1998 this is identical to the above statement. Added to
 424 c**** avoid questional branching to block.
 425               IF((NFP(JP,5).EQ.3 .AND.NFT(JT,5).EQ.3).OR.
 426      &           (NPJ(JP).NE.0.OR.NFP(JP,10).NE.0).OR.
 427      &           (NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) THEN
 428                  D1=DPX
 429                  D2=DTX
 430                  NFP3=0
 431                  NFT3=0
 432                  GO TO 400
 433               ENDIF
 434 C               ********do not allow excited strings to have
 435 C                       single-diffr
 436               IF(RLU_HIJING(0).GT.0.5.OR.(NFT(JT,5).GT.2.OR.
 437      &                NTJ(JT).NE.0.OR.NFT(JT,10).NE.0)) THEN
 438                  D1=DPN
 439                  D2=DTX
 440                  NFP3=NFP(JP,3)
 441                  NFT3=0
 442                  GO TO 220
 443               ELSE
 444                  D1=DPX
 445                  D2=DTN
 446                  NFP3=0
 447                  NFT3=NFT(JT,3)
 448                  GO TO 240
 449               ENDIF
 450 C               ********have single diffractive collision
 451            ENDIF
 452         ELSE IF(SW.GT.MAX(SPDTX,SPXTD)+0.001 .AND.
 453      &                          SW.LE.SXX+0.001) THEN
 454            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0.AND.
 455      &         RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 456      &         .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 457               D1=DPD
 458               D2=DTX
 459               NFP3=NFDP
 460               NFT3=0
 461               GO TO 220
 462            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 463               D1=DPX
 464               D2=DTD
 465               NFP3=0
 466               NFT3=NFDT
 467               GO TO 240
 468            ENDIF
 469            GO TO 4000
 470         ELSE IF(SW.GT.MIN(SPDTX,SPXTD)+0.001.AND.
 471      &                  SW.LE.MAX(SPDTX,SPXTD)+0.001) THEN
 472            IF(SPDTX.LE.SPXTD.AND.NPJ(JP).EQ.0
 473      &                       .AND.NFP(JP,5).LE.2) THEN
 474               D1=DPD
 475               D2=DTX
 476               NFP3=NFDP
 477               NFT3=0
 478               GO TO 220
 479            ELSE IF(SPDTX.GT.SPXTD.AND.NTJ(JT).EQ.0
 480      &                       .AND.NFT(JT,5).LE.2) THEN
 481               D1=DPX
 482               D2=DTD
 483               NFP3=0
 484               NFT3=NFDT
 485               GO TO 240
 486            ENDIF
 487 c*** 5/30/1998 added to avoid questional branching to another block
 488 c*** this is identical to the statement following the next ELSE IF
 489            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0
 490      &       .AND.RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 491      &        .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 492               D1=DPN
 493               D2=DTX
 494               NFP3=NFP(JP,3)
 495               NFT3=0
 496               GO TO 220
 497            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 498               D1=DPX
 499               D2=DTN
 500               NFP3=0
 501               NFT3=NFT(JT,3)
 502               GO TO 240
 503            ENDIF
 504            GO TO 4000
 505         ELSE IF(SW.GT.MAX(SPNTX,SPXTN)+0.001 .AND.
 506      &                  SW.LE.MIN(SPDTX,SPXTD)+0.001) THEN
 507            IF(((NPJ(JP).EQ.0.AND.NTJ(JT).EQ.0
 508      &       .AND.RLU_HIJING(0).GT.0.5).OR.(NPJ(JP).EQ.0
 509      &        .AND.NTJ(JT).NE.0)).AND.NFP(JP,5).LE.2) THEN
 510               D1=DPN
 511               D2=DTX
 512               NFP3=NFP(JP,3)
 513               NFT3=0
 514               GO TO 220
 515            ELSE IF(NTJ(JT).EQ.0.AND.NFT(JT,5).LE.2) THEN
 516               D1=DPX
 517               D2=DTN
 518               NFP3=0
 519               NFT3=NFT(JT,3)
 520               GO TO 240
 521            ENDIF
 522            GO TO 4000
 523         ELSE IF(SW.GT.MIN(SPNTX,SPXTN)+0.001 .AND.
 524      &                  SW.LE.MAX(SPNTX,SPXTN)+0.001) THEN
 525            IF(SPNTX.LE.SPXTN.AND.NPJ(JP).EQ.0
 526      &                           .AND.NFP(JP,5).LE.2) THEN
 527               D1=DPN
 528               D2=DTX
 529               NFP3=NFP(JP,3)
 530               NFT3=0
 531               GO TO 220
 532            ELSEIF(SPNTX.GT.SPXTN.AND.NTJ(JT).EQ.0
 533      &                           .AND.NFT(JT,5).LE.2) THEN
 534               D1=DPX
 535               D2=DTN
 536               NFP3=0
 537               NFT3=NFT(JT,3)
 538               GO TO 240
 539            ENDIF
 540            GO TO 4000
 541         ELSE IF(SW.LE.MIN(SPNTX,SPXTN)+0.001 .AND.
 542      &                  (NPJ(JP).NE.0 .OR.NTJ(JT).NE.0)) THEN
 543            GO TO 4000
 544         ELSE IF(SW.LE.MIN(SPNTX,SPXTN)+0.001 .AND.
 545      &          NFP(JP,5).GT.2.AND.NFT(JT,5).GT.2) THEN
 546            GO TO 4000
 547         ELSE IF(SW.GT.SDD+0.001.AND.SW.LE.
 548      &                     MIN(SPNTX,SPXTN)+0.001) THEN
 549            D1=DPD
 550            D2=DTD
 551            NFP3=NFDP
 552            NFT3=NFDT
 553            GO TO 100
 554         ELSE IF(SW.GT.MAX(SPNTD,SPDTN)+0.001
 555      &                      .AND. SW.LE.SDD+0.001) THEN
 556            IF(RLU_HIJING(0).GT.0.5) THEN
 557               D1=DPD
 558               D2=DTN
 559               NFP3=NFDP
 560               NFT3=NFT(JT,3)
 561               GO TO 100
 562            ELSE
 563               D1=DPN
 564               D2=DTD
 565               NFP3=NFP(JP,3)
 566               NFT3=NFDT
 567               GO TO 100
 568            ENDIF
 569         ELSE IF(SW.GT.MIN(SPNTD,SPDTN)+0.001
 570      &          .AND. SW.LE.MAX(SPNTD,SPDTN)+0.001) THEN
 571            IF(SPNTD.GT.SPDTN) THEN
 572               D1=DPD
 573               D2=DTN
 574               NFP3=NFDP
 575               NFT3=NFT(JT,3)
 576               GO TO 100
 577            ELSE
 578               D1=DPN
 579               D2=DTD
 580               NFP3=NFP(JP,3)
 581               NFT3=NFDT
 582               GO TO 100
 583            ENDIF
 584         ELSE IF(SW.LE.MIN(SPNTD,SPDTN)+0.001) THEN
 585            D1=DPN
 586            D2=DTN
 587            NFP3=NFP(JP,3)
 588            NFT3=NFT(JT,3)
 589            GO TO 100
 590         ENDIF
 591         WRITE(6,*) ' Error in HIJSFT: There is no path to here'
 592         RETURN
 593 C
 594 C***************  elastic scattering ***************
 595 C       this is like elastic, both proj and targ mass
 596 C       must be fixed
 597 C***************************************************
 598 100     NFP5=MAX(2,NFP(JP,5))
 599         NFT5=MAX(2,NFT(JT,5))
 600         BB1=1.0+D1-D2
 601         BB2=1.0+D2-D1
 602         IF(BB1**2.LT.4.0*D1 .OR. 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         IF(RLU_HIJING(0).LT.0.5) THEN
 609                 X1=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 610                 X2=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 611         ELSE
 612                 X1=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 613                 X2=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 614         ENDIF
 615         IHNT2(13)=2
 616         GO TO 600
 617 C
 618 C********** Single diffractive ***********************
 619 C either proj or targ's mass is fixed
 620 C*****************************************************
 621 220     NFP5=MAX(2,NFP(JP,5))
 622         NFT5=3
 623         IF(NFP3.EQ.0) NFP5=3
 624         BB2=1.0+D2-D1
 625         IF(BB2**2.LT.4.0*D2) 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=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 632         XMAX=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 633         MISS4=0
 634 222     X2=HIRND2(6,XMIN,XMAX)
 635         X1=D1/(1.0-X2)
 636         IF(X2*(1.0-X1).LT.(D2+1.E-4/SW)) THEN
 637                 MISS4=MISS4+1
 638                 IF(MISS4.LE.1000) GO TO 222
 639                 GO TO 5000
 640         ENDIF
 641         IHNT2(13)=2
 642         GO TO 600
 643 C                       ********Fix proj mass*********
 644 240     NFP5=3
 645         NFT5=MAX(2,NFT(JT,5))
 646         IF(NFT3.EQ.0) NFT5=3
 647         BB1=1.0+D1-D2
 648         IF(BB1**2.LT.4.0*D1) THEN
 649                 MISS=MISS+1
 650                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 651                 PKC=PKC*0.5
 652                 GO TO 30
 653         ENDIF
 654         XMIN=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 655         XMAX=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 656         MISS4=0
 657 242     X1=HIRND2(6,XMIN,XMAX)
 658         X2=D2/(1.0-X1)
 659         IF(X1*(1.0-X2).LT.(D1+1.E-4/SW)) THEN
 660                 MISS4=MISS4+1
 661                 IF(MISS4.LE.1000) GO TO 242
 662                 GO TO 5000
 663         ENDIF
 664         IHNT2(13)=2
 665         GO TO 600
 666 C                       ********Fix targ mass*********
 667 C
 668 C*************non-single diffractive**********************
 669 C       both proj and targ may not be fixed in mass
 670 C*********************************************************
 671 C
 672 400     NFP5=3
 673         NFT5=3
 674         BB1=1.0+D1-D2
 675         BB2=1.0+D2-D1
 676         IF(BB1**2.LT.4.0*D1 .OR. BB2**2.LT.4.0*D2) THEN
 677                 MISS=MISS+1
 678                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 3000
 679                 PKC=PKC*0.5
 680                 GO TO 30
 681         ENDIF
 682         XMIN1=(BB1-SQRT(BB1**2-4.0*D1))/2.0
 683         XMAX1=(BB1+SQRT(BB1**2-4.0*D1))/2.0
 684         XMIN2=(BB2-SQRT(BB2**2-4.0*D2))/2.0
 685         XMAX2=(BB2+SQRT(BB2**2-4.0*D2))/2.0
 686         MISS4=0
 687 410     X1=HIRND2(4,XMIN1,XMAX1)
 688         X2=HIRND2(4,XMIN2,XMAX2)
 689         IF(NFP(JP,5).EQ.3.OR.NFT(JT,5).EQ.3) THEN
 690                 X1=HIRND2(6,XMIN1,XMAX1)
 691                 X2=HIRND2(6,XMIN2,XMAX2)
 692         ENDIF
 693 C                       ********
 694         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000.OR.
 695      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.100) THEN
 696                 X1=HIRND2(5,XMIN1,XMAX1)
 697         ENDIF
 698         IF(ABS(NFT(JT,1)*NFT(JT,2)).GT.1000000.OR.
 699      &                  ABS(NFT(JT,1)*NFT(JT,2)).LT.100) THEN
 700                 X2=HIRND2(5,XMIN2,XMAX2)
 701         ENDIF
 702 c       IF(IOPMAIN.EQ.3) X1=HIRND2(6,XMIN1,XMAX1)
 703 c       IF(IOPMAIN.EQ.2) X2=HIRND2(6,XMIN2,XMAX2)
 704 C       ********For q-qbar or (qq)-(qq)bar system use symetric
 705 C               distribution, for q-(qq) or qbar-(qq)bar use
 706 C               unsymetrical distribution
 707 C
 708         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000) X1=1.0-X1
 709         XXP=X1*(1.0-X2)
 710         XXT=X2*(1.0-X1)
 711         IF(XXP.LT.(D1+1.E-4/SW) .OR. XXT.LT.(D2+1.E-4/SW)) THEN
 712                 MISS4=MISS4+1
 713                 IF(MISS4.LE.1000) GO TO 410
 714                 GO TO 5000
 715         ENDIF
 716         IHNT2(13)=3
 717 C***************************************************
 718 C***************************************************
 719 600     CONTINUE
 720         IF(X1*(1.0-X2).LT.(AMPN**2-1.E-4)/SW.OR.
 721      &                  X2*(1.0-X1).LT.(AMTN**2-1.E-4)/SW) THEN
 722                 MISS=MISS+1
 723                 IF(MISS.GT.100.OR.PKC.EQ.0.0) GO TO 2000
 724                 PKC=0.0
 725                 GO TO 30
 726         ENDIF
 727 C
 728         EPP=(1.0-X2)*WP
 729         EPM=X1*WM
 730         ETP=X2*WP
 731         ETM=(1.0-X1)*WM
 732         PP(JP,3)=(EPP-EPM)/2.0
 733         PP(JP,4)=(EPP+EPM)/2.0
 734         IF(EPP*EPM-PTP2.LT.0.0) GO TO 6000
 735         PP(JP,5)=SQRT(EPP*EPM-PTP2)
 736         NFP(JP,3)=NFP3
 737         NFP(JP,5)=NFP5
 738
 739         PT(JT,3)=(ETP-ETM)/2.0
 740         PT(JT,4)=(ETP+ETM)/2.0
 741         IF(ETP*ETM-PTT2.LT.0.0) GO TO 6000
 742         PT(JT,5)=SQRT(ETP*ETM-PTT2)
 743         NFT(JT,3)=NFT3
 744         NFT(JT,5)=NFT5
 745 C*****recoil PT from hard-inter is shared by two end-partons
 746 C       so that pt=p1+p2
 747         PP(JP,1)=PP11-PKC11
 748         PP(JP,2)=PP12-PKC12
 749
 750         KICKDIP=1
 751         KICKDIT=1
 752         IF(ABS(NFP(JP,1)*NFP(JP,2)).GT.1000000.OR.
 753      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.100) THEN
 754                 KICKDIP=0
 755         ENDIF
 756         IF(ABS(NFT(JT,1)*NFT(JT,2)).GT.1000000.OR.
 757      &                  ABS(NFT(JT,1)*NFT(JT,2)).LT.100) THEN
 758                 KICKDIT=0
 759         ENDIF
 760         IF((KICKDIP.EQ.0.AND.RLU_HIJING(0).LT.0.5)
 761      &     .OR.(KICKDIP.NE.0.AND.RLU_HIJING(0)
 762      &     .LT.0.5/(1.0+(PKC11**2+PKC12**2)/HIPR1(22)**2))) THEN
 763            PP(JP,6)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0+PP(JP,6)
 764            PP(JP,7)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0+PP(JP,7)
 765            PP(JP,8)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0
 766      &              +PP(JP,8)+PKC11
 767            PP(JP,9)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0
 768      &              +PP(JP,9)+PKC12
 769         ELSE
 770            PP(JP,8)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0+PP(JP,8)
 771            PP(JP,9)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0+PP(JP,9)
 772            PP(JP,6)=(PP(JP,1)-PP(JP,6)-PP(JP,8)-DPKC1)/2.0
 773      &              +PP(JP,6)+PKC11
 774            PP(JP,7)=(PP(JP,2)-PP(JP,7)-PP(JP,9)-DPKC2)/2.0
 775      &              +PP(JP,7)+PKC12
 776         ENDIF
 777         PP(JP,1)=PP(JP,6)+PP(JP,8)
 778         PP(JP,2)=PP(JP,7)+PP(JP,9)
 779 C                               ********pt kick for proj
 780         PT(JT,1)=PT11-PKC21
 781         PT(JT,2)=PT12-PKC22
 782         IF((KICKDIT.EQ.0.AND.RLU_HIJING(0).LT.0.5)
 783      &     .OR.(KICKDIT.NE.0.AND.RLU_HIJING(0)
 784      &     .LT.0.5/(1.0+(PKC21**2+PKC22**2)/HIPR1(22)**2))) THEN
 785            PT(JT,6)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0+PT(JT,6)
 786            PT(JT,7)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0+PT(JT,7)
 787            PT(JT,8)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0
 788      &              +PT(JT,8)+PKC21
 789            PT(JT,9)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0
 790      &              +PT(JT,9)+PKC22
 791         ELSE
 792            PT(JT,8)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0+PT(JT,8)
 793            PT(JT,9)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0+PT(JT,9)
 794            PT(JT,6)=(PT(JT,1)-PT(JT,6)-PT(JT,8)-DPKC1)/2.0
 795      &              +PT(JT,6)+PKC21
 796            PT(JT,7)=(PT(JT,2)-PT(JT,7)-PT(JT,9)-DPKC2)/2.0
 797      &              +PT(JT,7)+PKC22
 798         ENDIF
 799         PT(JT,1)=PT(JT,6)+PT(JT,8)
 800         PT(JT,2)=PT(JT,7)+PT(JT,9)
 801 C                       ********pt kick for targ
 802
 803         IF(NPJ(JP).NE.0) NFP(JP,5)=3
 804         IF(NTJ(JT).NE.0) NFT(JT,5)=3
 805 C                       ********jets must be connected to string
 806         IF(EPP/(EPM+0.0001).LT.ETP/(ETM+0.0001).AND.
 807      &                  ABS(NFP(JP,1)*NFP(JP,2)).LT.1000000)THEN
 808                 DO 620 JSB=1,15
 809                 PSB=PP(JP,JSB)
 810                 PP(JP,JSB)=PT(JT,JSB)
 811                 PT(JT,JSB)=PSB
 812                 NSB=NFP(JP,JSB)
 813                 NFP(JP,JSB)=NFT(JT,JSB)
 814                 NFT(JT,JSB)=NSB
 815 620             CONTINUE
 816 C               ********when Ycm(JP)<Ycm(JT) after the collision
 817 C                       exchange the positions of the two
 818         ENDIF
 819 C
 820         RETURN
 821 C**************************************************
 822 C**************************************************
 823 1000    IERROR=1
 824         IF(IHPR2(10).EQ.0) RETURN
 825         WRITE(6,*) '    Fatal HIJSFT start error,abandon this event'
 826         WRITE(6,*) '    PROJ E+,E-,W+',EPP,EPM,WP
 827         WRITE(6,*) '    TARG E+,E-,W-',ETP,ETM,WM
 828         WRITE(6,*) '    W+*W-, (APN+ATN)^2',SW,SNN
 829         RETURN
 830 2000    IERROR=0
 831         IF(IHPR2(10).EQ.0) RETURN
 832         WRITE(6,*) '    (2)energy partition fail,'
 833         WRITE(6,*) '    HIJSFT not performed, but continue'
 834         WRITE(6,*) '    MP1,MPN',X1*(1.0-X2)*SW,AMPN**2
 835         WRITE(6,*) '    MT2,MTN',X2*(1.0-X1)*SW,AMTN**2
 836         RETURN
 837 3000    IERROR=0
 838         IF(IHPR2(10).EQ.0) RETURN
 839         WRITE(6,*) '    (3)something is wrong with the pt kick, '
 840         WRITE(6,*) '    HIJSFT not performed, but continue'
 841         WRITE(6,*) '    D1=',D1,' D2=',D2,' SW=',SW
 842         WRITE(6,*) '    HISTORY NFP5=',NFP(JP,5),' NFT5=',NFT(JT,5)
 843         WRITE(6,*) '    THIS COLLISON NFP5=',NFP5, ' NFT5=',NFT5
 844         WRITE(6,*) '    # OF JET IN PROJ',NPJ(JP),' IN TARG',NTJ(JT)
 845         RETURN
 846 4000    IERROR=0
 847         IF(IHPR2(10).EQ.0) RETURN
 848         WRITE(6,*) '    (4)unable to choose process, but not harmful'
 849         WRITE(6,*) '    HIJSFT not performed, but continue'
 850         WRITE(6,*) '    PTP=',SQRT(PTP2),' PTT=',SQRT(PTT2),' SW=',SW
 851         WRITE(6,*) '    AMCUT=',AMX,' JP=',JP,' JT=',JT
 852         WRITE(6,*) '    HISTORY NFP5=',NFP(JP,5),' NFT5=',NFT(JT,5)
 853         RETURN
 854 5000    IERROR=0
 855         IF(IHPR2(10).EQ.0) RETURN
 856         WRITE(6,*) '    energy partition failed(5),for limited try'
 857         WRITE(6,*) '    HIJSFT not performed, but continue'
 858         WRITE(6,*) '    NFP5=',NFP5,' NFT5=',NFT5
 859         WRITE(6,*) '    D1',D1,' X1(1-X2)',X1*(1.0-X2)
 860         WRITE(6,*) '    D2',D2,' X2(1-X1)',X2*(1.0-X1)
 861         RETURN
 862 6000    PKC=0.0
 863         MISS=MISS+1
 864         IF(MISS.LT.100) GO TO 30
 865         IERROR=1
 866         IF(IHPR2(10).EQ.0) RETURN
 867         WRITE(6,*) ' ERROR OCCURED, HIJSFT NOT PERFORMED'
 868         WRITE(6,*) ' Abort this event'
 869         WRITE(6,*) 'MTP,PTP2',EPP*EPM,PTP2,'  MTT,PTT2',ETP*ETM,PTT2
 870         RETURN
 871         END