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