PYTHIA6/QPYTHIA/q-pyshow.1.2.F

   1 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
   2 C
   3 C     AUXILIARY ROUTINES FOR Q-PYTHIA version 1.0.
   4 C
   5 C     DATE: 26.09.2008.
   6 C
   7 C     AUTHORS: N. Armesto, L. Cunqueiro and C. A. Salgado
   8 C              Departamento de Fisica de Particulas and IGFAE
   9 C              Universidade de Santiago de Compostela
  10 C              15706 Santiago de Compostela, Spain
  11 C
  12 C     EMAILS: nestor@fpaxp1.usc.es, leticia@fpaxp1.usc.es,
  13 C             Carlos.Salgado@cern.ch
  14 C
  15 C     CONTENT: auxiliary files for modified PYSHOW, fixed to PYTHIA-6.4.18.
  16 C              NOT to be modified by user.
  17 C
  18 C     WHEN USING Q-PYTHIA, PLEASE QUOTE:
  19 C
  20 C     1) N. Armesto, G. Corcella, L. Cunqueiro and C. A. Salgado,
  21 C        in preparation.
  22 C     2) T. Sjostrand, S. Mrenna and P. Skands,
  23 C        ``PYTHIA 6.4 physics and manual,''
  24 C        JHEP 0605 (2006) 026 [arXiv:hep-ph/0603175].
  25 C
  26 C     DISCLAIMER: this program comes without any guarantees. Beware of
  27 C                 errors and use common sense when interpreting results.
  28 C                 Any modifications are done under exclusive
  29 C                 maker's resposibility.
  30 C
  31 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
  32 C
  33 c     VERSION WITH THE LARGE X BEHAVIOR OF THE MEDIUM PART INTRODUCED
  34 C     BY MULTIPLYING BY THE NUMERATOR OF THE COLLINEAR PART OF THE
  35 C     VACUUM SPLITTING FUNCTION
  36 c
  37       function splitq1(w)
  38 c     to integrate, adding vaccum plus medium q -> qg
  39       implicit double precision (a-h,o-z)
  40       z=w
  41       auxz=z*(1.d0-z)
  42       auxq=splitgq(z)+splitmedq1(z)
  43       if (auxq .gt. 0.d0) then
  44          splitq1=auxq
  45       else
  46          splitq1=0.d0
  47       endif
  48       return
  49       end
  50 c
  51       function splitg1(w)
  52 c     to integrate, adding vaccum plus medium g -> gg, and g -> qqbar
  53       implicit double precision (a-h,o-z)
  54       z=w
  55       auxz=z*(1.d0-z)
  56 c     argument of running coupling is taken as kt of emission
  57       auxg=splitgg(z)+splitmedg1(z)
  58       if (auxg .gt. 0.d0) then
  59          splitg1=(auxg+splitqqbar(z))
  60       else
  61          splitg1=splitqqbar(z)
  62       endif
  63       return
  64       end
  65 c
  66       function splitq2(w)
  67 c     to integrate, adding vaccum plus medium q -> qg
  68       implicit double precision (a-h,o-z)
  69       z=w
  70       auxq=splitgq(z)+splitmedq2(z)
  71       if (auxq .gt. 0.d0) then
  72          splitq2=auxq
  73       else
  74          splitq2=0.d0
  75       endif
  76       if(splitmedq2(z).eq.0.) then
  77       endif
  78       return
  79       end
  80 c
  81       function splitg2(z)
  82 c     to integrate, adding vaccum plus medium g -> gg, and g -> qqbar
  83       implicit double precision (a-h,o-z)
  84       auxg=splitgg(z)+splitmedg2(z)
  85       if(auxg.gt.0.d0) then
  86       splitg2=auxg
  87       else
  88       splitg2=0.d0
  89       endif
  90       if(splitmedg2(z).eq.0.) then
  91       endif
  92       return
  93       end
  94 c
  95       function splitgq(z)
  96 c     q -> qg splitting kernel at 1 loop for the vacuum
  97       implicit double precision (a-h,o-z)
  98       xnc=3.d0
  99       splitgq=(0.5d0*(xnc-1.d0/xnc))*(1.d0+z*z)/(1.d0-z)
 100       return
 101       end
 102 c
 103       function splitgg(z)
 104 c     g -> gg splitting kernel at 1 loop for the vacuum
 105       implicit double precision (a-h,o-z)
 106       xnc=3.d0
 107       auxz=z*(1.d0-z)
 108       auxz2=1.d0-auxz
 109       splitgg=xnc*auxz2*auxz2/auxz
 110       return
 111       end
 112 c
 113       function splitqqbar(z)
 114 c     g -> qqbar splitting kernel at 1 loop
 115       implicit double precision (a-h,o-z)
 116       xnf=5.d0
 117       auxz=1.d0-z
 118       splitqqbar=0.5d0*xnf*(z*z+auxz*auxz)
 119       return
 120       end
 121 c
 122       function splitmedg1(z)
 123 c     g -> gg splitting kernel at 1 loop for the medium
 124       implicit double precision (a-h,o-z)
 125       common/qpc1/eee,qhatl,omegac
 126       common/qpvir1/pmed
 127       xnc=3.d0
 128       pi=dacos(-1.d0)
 129       if (qhatl .le. 0.d0 .or. omegac .le. 0.d0) then
 130          splitmedg1=0.d0
 131       else
 132 c     symmetrized by hand with respect to 1/2
 133          if (z .ge. 0.5d0) then
 134             zz=z
 135          else
 136             zz=1.d0-z
 137          endif
 138          t=pmed*pmed
 139          auxz=1.d0-zz
 140          auxz2=zz*auxz
 141          ome=eee*auxz/omegac
 142          xkappa2=auxz2*t/qhatl
 143          fff=genspec(ome,xkappa2)
 144 cc     1/2 to avoid double counting
 145 c         splitmedg=0.5d0*xnc*2.d0*pi*zz*t*fff/qhatl
 146 c     we multiply by max(z,1-z) to introduce the large z behavior from the
 147 c     numerator in the vacuum
 148          flx=max(zz,auxz)
 149 c     1/2 to avoid double counting
 150          splitmedg1=0.5*flx*xnc*2.d0*pi*zz*t*fff/qhatl
 151       endif
 152       return
 153       end
 154 c
 155       function splitmedq1(z)
 156 c     q -> qg splitting kernel at 1 loop for the medium
 157       implicit double precision (a-h,o-z)
 158       common/qpc1/eee,qhatl,omegac
 159       common/qpvir1/pmed
 160       xnc=3.d0
 161       pi=dacos(-1.d0)
 162       if (qhatl .le. 0.d0 .or. omegac .le. 0.d0) then
 163          splitmedq1=0.d0
 164       else
 165          t=pmed*pmed
 166          auxz=1.d0-z
 167          auxz2=z*auxz
 168          ome=eee*auxz/omegac
 169          xkappa2=auxz2*t/qhatl
 170          fff=genspec(ome,xkappa2)
 171 c         splitmedq=(0.5d0*(xnc-1.d0/xnc))*2.d0*pi*z*t*fff/qhatl
 172 c     we multiply by 1+z**2 to introduce the large z behavior from the
 173 c     numerator in the vacuum
 174          flx=0.5d0*(1.d0+z*z)
 175          splitmedq1=flx*(0.5d0*(xnc-1.d0/xnc))*2.d0*pi*z*t*fff/qhatl
 176       endif
 177       return
 178       end
 179 c
 180       function splitmedg2(z)
 181 c     g -> gg splitting kernel at 1 loop for the medium
 182       implicit double precision (a-h,o-z)
 183       common/qpc1/eee,qhatl,omegac
 184       common/qpvir2/virt
 185       xnc=3.d0
 186       pi=dacos(-1.d0)
 187       if (qhatl .le. 0.d0 .or. omegac .le. 0.d0) then
 188          splitmedg2=0.d0
 189       else
 190 c     symmetrized by hand with respect to 1/2
 191          if (z .ge. 0.5d0) then
 192             zz=z
 193          else
 194             zz=1.d0-z
 195          endif
 196          t=virt
 197          auxz=1.d0-zz
 198          auxz2=zz*auxz
 199          ome=eee*auxz/omegac
 200          xkappa2=auxz2*t/qhatl
 201          fff=genspec(ome,xkappa2)
 202 cc     1/2 to avoid double counting
 203 c         splitmedg=0.5d0*xnc*2.d0*pi*zz*t*fff/qhatl
 204 c     we multiply by max(z,1-z) to introduce the large z behavior from the
 205 c     numerator in the vacuum
 206          flx=max(zz,auxz)
 207 c     1/2 to avoid double counting
 208          splitmedg2=0.5*flx*xnc*2.d0*pi*zz*t*fff/qhatl
 209       endif
 210       return
 211       end
 212 c
 213       function splitmedq2(z)
 214 c     q -> qg splitting kernel at 1 loop for the medium
 215       implicit double precision (a-h,o-z)
 216       common/qpc1/eee,qhatl,omegac
 217       common/qpvir2/virt
 218       xnc=3.d0
 219       pi=dacos(-1.d0)
 220       if (qhatl .le. 0.d0 .or. omegac .le. 0.d0) then
 221          splitmedq2=0.d0
 222       else
 223          t=virt
 224          auxz=1.d0-z
 225          auxz2=z*auxz
 226          ome=eee*auxz/omegac
 227          xkappa2=auxz2*t/qhatl
 228          fff=genspec(ome,xkappa2)
 229 c         splitmedq=(0.5d0*(xnc-1.d0/xnc))*2.d0*pi*z*t*fff/qhatl
 230 c     we multiply by 1+z**2 to introduce the large z behavior from the
 231 c     numerator in the vacuum
 232          flx=0.5d0*(1.d0+z*z)
 233          splitmedq2=flx*(0.5d0*(xnc-1.d0/xnc))*2.d0*pi*z*t*fff/qhatl
 234       endif
 235       return
 236       end
 237 c
 238       function genspec(ome,xk2)
 239 C     THIS FUNCTION GENERATES (omega/omegac) dI/d(omega/omegac) dkappa2,
 240 C     omegac=qhat L/2, kappa2=kt2/(qhat L), in the mss approximation for m=0,
 241 c     using interpolation and extrapolation. It reads file grid-qp.dat.
 242 c     ome=omega/omegac, xk2=kappa2.
 243 C     MAXIMUM GRID 101 TIMES 101, MODIFY ARRAY DIMENSIONS IF EXCEEDED.
 244 c     alphas=1, cr=1.
 245       implicit double precision (a-h,o-z)
 246       dimension xkap2(101), xlkap2(101), xome(101), xlome(101)
 247       dimension xspec(101,101)
 248       dimension aux1(101), aux2(101)
 249       save xkap2, xlkap2, xome, xlome, xspec, npkap, npome
 250       character*1000 filnam
 251       character*1000 chroot
 252       DATA IFLAG/0/
 253 c     WE READ THE GRID ONLY THE FIRST TIME.
 254       IF (IFLAG .EQ. 0) THEN
 255          chroot=' '
 256          call getenvf('ALICE_ROOT',chroot)
 257          lnroot= lnblnk(chroot)
 258          filnam=chroot(1:lnroot)//'/PYTHIA6/QPYTHIA/qgrid'
 259          write(6,*) "Opening file ", filnam
 260          open(11,file=filnam, status='old')
 261          read(11,*) npkap
 262          read(11,*) npome
 263          npkap=npkap+1
 264          npome=npome+1
 265          do 10 i=1, npkap, 1
 266             read(11,*) xkap2(i), xlkap2(i)
 267 10       continue
 268          do 20 i=1, npome, 1
 269             read(11,*) xome(i), xlome(i)
 270 20       continue
 271          do 30 j=1, npome, 1
 272             do 40 i=1, npkap, 1
 273                read(11,*) xspec(i,j)
 274 40          continue
 275 30       continue
 276          close(11)
 277          iflag=1
 278       ENDIF
 279 c     cases
 280 c     for ome>largest value set to 0,
 281 c     for xk2< smallest value frozen,
 282 c     for xk2> largest value 1/kappa4 extrapolation.
 283       if (ome .gt. xome(npome)) then
 284          genspec=0.d0
 285       elseif (ome .lt. xome(1)) then
 286          scal=.05648d0*dexp(1.674d0*ome)*dlog(.136d0/ome)/(ome**.5397d0)
 287          scal=0.25d0*9.d0*scal/xspec(1,1)
 288          if (xk2 .le. xkap2(1)) then
 289             genspec=scal*xspec(1,1)
 290          elseif (xk2 .eq. xkap2(npkap)) then
 291             genspec=scal*xspec(npkap,1)
 292          elseif (xk2 .gt. xkap2(npkap)) then
 293             genspec=scal*xspec(npkap,1)*
 294      >              xkap2(npkap)*xkap2(npkap)/(xk2*xk2)
 295          else
 296             do 50 i=1, npkap, 1
 297                aux1(i)=xspec(i,1)
 298 50          continue
 299             genspec=scal*ddivdif(aux1,xlkap2,npkap,dlog(xk2),4)
 300          endif
 301       else
 302          iexact=-1
 303          if (ome .eq. xome(1)) then
 304             iexact=1
 305             goto 70
 306          else
 307             do 60 i=1, npome-1, 1
 308                if (ome .eq. xome(i+1)) then
 309                   iexact=i+1
 310                   goto 70
 311                elseif (ome .lt. xome(i+1)) then
 312                   iprev=i
 313                   ipost=i+1
 314                   goto 70
 315                endif
 316 60          continue
 317 70          continue
 318          endif
 319          if (iexact .gt. 0) then
 320             if (xk2 .le. xkap2(1)) then
 321                genspec=xspec(1,iexact)
 322             elseif (xk2 .eq. xkap2(npkap)) then
 323                genspec=xspec(npkap,iexact)
 324             elseif (xk2 .gt. xkap2(npkap)) then
 325                genspec=xspec(npkap,iexact)*
 326      >                 xkap2(npkap)*xkap2(npkap)/(xk2*xk2)
 327             else
 328                do 80 i=1, npkap, 1
 329                   aux1(i)=xspec(i,iexact)
 330 80             continue
 331                genspec=ddivdif(aux1,xlkap2,npkap,dlog(xk2),4)
 332             endif
 333          else
 334             if (xk2 .le. xkap2(1)) then
 335                genprev=xspec(1,iprev)
 336                genpost=xspec(1,ipost)
 337             elseif (xk2 .eq. xkap2(npkap)) then
 338                genprev=xspec(npkap,iprev)
 339                genpost=xspec(npkap,ipost)
 340             elseif (xk2 .gt. xkap2(npkap)) then
 341                genprev=xspec(npkap,iprev)*
 342      >                 xkap2(npkap)*xkap2(npkap)/(xk2*xk2)
 343                genpost=xspec(npkap,ipost)*
 344      >                 xkap2(npkap)*xkap2(npkap)/(xk2*xk2)
 345             else
 346                do 90 i=1, npkap, 1
 347                   aux1(i)=xspec(i,iprev)
 348                   aux2(i)=xspec(i,ipost)
 349 90             continue
 350                genprev=ddivdif(aux1,xlkap2,npkap,dlog(xk2),4)
 351                genpost=ddivdif(aux2,xlkap2,npkap,dlog(xk2),4)
 352             endif
 353             g12=genprev-genpost
 354             xl12=xlome(iprev)-xlome(ipost)
 355             c1=g12/xl12
 356             c2=genprev-c1*xlome(iprev)
 357             genspec=c1*dlog(ome)+c2
 358          endif
 359       endif
 360 c
 361       RETURN
 362       END
 363 C
 364 *
 365 * $Id: divdif.F,v 1.1.1.1 1996/02/15 17:48:36 mclareni Exp $
 366 *
 367 * $Log: divdif.F,v $
 368 * Revision 1.1.1.1  1996/02/15 17:48:36  mclareni
 369 * Kernlib
 370 *
 371 *
 372       FUNCTION DDIVDIF(F,A,NN,X,MM)
 373 c     copy of cernlib divdif in double precision.
 374       implicit double precision (a-h,o-z)
 375       DIMENSION A(NN),F(NN),T(20),D(20)
 376       LOGICAL EXTRA
 377       LOGICAL MFLAG,RFLAG
 378       DATA MMAX/10/
 379 C
 380 C  TABULAR INTERPOLATION USING SYMMETRICALLY PLACED ARGUMENT POINTS.
 381 C
 382 C  START.  FIND SUBSCRIPT IX OF X IN ARRAY A.
 383       IF( (NN.LT.2) .OR. (MM.LT.1) ) GO TO 601
 384       N=NN
 385       M=MIN0(MM,MMAX,N-1)
 386       MPLUS=M+1
 387       IX=0
 388       IY=N+1
 389       IF(A(1).GT.A(N)) GO TO 4
 390 C     (SEARCH INCREASING ARGUMENTS.)
 391     1    MID=(IX+IY)/2
 392          IF(X.GE.A(MID)) GO TO 2
 393             IY=MID
 394             GO TO 3
 395 C        (IF TRUE.)
 396     2       IX=MID
 397     3    IF(IY-IX.GT.1) GO TO 1
 398          GO TO 7
 399 C     (SEARCH DECREASING ARGUMENTS.)
 400     4    MID=(IX+IY)/2
 401          IF(X.LE.A(MID)) GO TO 5
 402             IY=MID
 403             GO TO 6
 404 C        (IF TRUE.)
 405     5       IX=MID
 406     6    IF(IY-IX.GT.1) GO TO 4
 407 C
 408 C  COPY REORDERED INTERPOLATION POINTS INTO (T(I),D(I)), SETTING
 409 C  *EXTRA* TO TRUE IF M+2 POINTS TO BE USED.
 410     7 NPTS=M+2-MOD(M,2)
 411       IP=0
 412       L=0
 413       GO TO 9
 414     8    L=-L
 415          IF(L.GE.0) L=L+1
 416     9    ISUB=IX+L
 417          IF((1.LE.ISUB).AND.(ISUB.LE.N)) GO TO 501
 418 C        (SKIP POINT.)
 419             NPTS=MPLUS
 420             GO TO 11
 421 C        (INSERT POINT.)
 422  501        IP=IP+1
 423             T(IP)=A(ISUB)
 424             D(IP)=F(ISUB)
 425    11    IF(IP.LT.NPTS) GO TO 8
 426       EXTRA=NPTS.NE.MPLUS
 427 C
 428 C  REPLACE D BY THE LEADING DIAGONAL OF A DIVIDED-DIFFERENCE TABLE, SUP-
 429 C  PLEMENTED BY AN EXTRA LINE IF *EXTRA* IS TRUE.
 430       DO 14 L=1,M
 431          IF(.NOT.EXTRA) GO TO 12
 432             ISUB=MPLUS-L
 433             D(M+2)=(D(M+2)-D(M))/(T(M+2)-T(ISUB))
 434    12    I=MPLUS
 435          DO 13 J=L,M
 436             ISUB=I-L
 437             D(I)=(D(I)-D(I-1))/(T(I)-T(ISUB))
 438             I=I-1
 439    13    CONTINUE
 440    14 CONTINUE
 441 C
 442 C  EVALUATE THE NEWTON INTERPOLATION FORMULA AT X, AVERAGING TWO VALUES
 443 C  OF LAST DIFFERENCE IF *EXTRA* IS TRUE.
 444       SUM=D(MPLUS)
 445       IF(EXTRA) SUM=0.5*(SUM+D(M+2))
 446       J=M
 447       DO 15 L=1,M
 448          SUM=D(J)+(X-T(J))*SUM
 449          J=J-1
 450    15 CONTINUE
 451       DDIVDIF=SUM
 452       RETURN
 453 C
 454  601  CALL KERMTR('E105.1',LGFILE,MFLAG,RFLAG)
 455       DDIVDIF=0
 456       IF(MFLAG) THEN
 457          IF(LGFILE.EQ.0) THEN
 458             IF(MM.LT.1) WRITE(*,101) MM
 459             IF(NN.LT.2) WRITE(*,102) NN
 460          ELSE
 461             IF(MM.LT.1) WRITE(LGFILE,101) MM
 462             IF(NN.LT.2) WRITE(LGFILE,102) NN
 463          ENDIF
 464       ENDIF
 465       IF(.NOT.RFLAG) CALL ABEND
 466       RETURN
 467   101 FORMAT( 7X, 'FUNCTION DDIVDIF ... M =',I6,' IS LESS THAN 1')
 468   102 FORMAT( 7X, 'FUNCTION DDIVDIF ... N =',I6,' IS LESS THAN 2')
 469       END
 470 c
 471 C     COPY OF CERN DGAUSS
 472 C
 473       FUNCTION DGAUSS1(F,A,B,EPS)
 474       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
 475       DIMENSION W(12),X(12)
 476       PARAMETER (Z1 = 1.D0, HF = Z1/2.D0, CST = 5.D0*Z1/1000.D0)
 477       DATA X
 478      1        /0.96028 98564 97536 23168 35608 68569 47D0,
 479      2         0.79666 64774 13626 73959 15539 36475 83D0,
 480      3         0.52553 24099 16328 98581 77390 49189 25D0,
 481      4         0.18343 46424 95649 80493 94761 42360 18D0,
 482      5         0.98940 09349 91649 93259 61541 73450 33D0,
 483      6         0.94457 50230 73232 57607 79884 15534 61D0,
 484      7         0.86563 12023 87831 74388 04678 97712 39D0,
 485      8         0.75540 44083 55003 03389 51011 94847 44D0,
 486      9         0.61787 62444 02643 74844 66717 64048 79D0,
 487      A         0.45801 67776 57227 38634 24194 42983 58D0,
 488      B         0.28160 35507 79258 91323 04605 01460 50D0,
 489      C         0.95012 50983 76374 40185 31933 54249 58D-1/
 490
 491       DATA W
 492      1        /0.10122 85362 90376 25915 25313 54309 96D0,
 493      2         0.22238 10344 53374 47054 43559 94426 24D0,
 494      3         0.31370 66458 77887 28733 79622 01986 60D0,
 495      4         0.36268 37833 78361 98296 51504 49277 20D0,
 496      5         0.27152 45941 17540 94851 78057 24560 18D-1,
 497      6         0.62253 52393 86478 92862 84383 69943 78D-1,
 498      7         0.95158 51168 24927 84809 92510 76022 46D-1,
 499      8         0.12462 89712 55533 87205 24762 82192 02D0,
 500      9         0.14959 59888 16576 73208 15017 30547 48D0,
 501      A         0.16915 65193 95002 53818 93120 79030 36D0,
 502      B         0.18260 34150 44923 58886 67636 67969 22D0,
 503      C         0.18945 06104 55068 49628 53967 23208 28D0/
 504       EXTERNAL F
 505       H=0.D0
 506       IF(B .EQ. A) GO TO 99
 507       CONST=CST/ABS(B-A)
 508       BB=A
 509     1 AA=BB
 510       BB=B
 511     2 C1=HF*(BB+AA)
 512       C2=HF*(BB-AA)
 513       S8=0.D0
 514       DO 3 I = 1,4
 515       U=C2*X(I)
 516     3 S8=S8+W(I)*(F(C1+U)+F(C1-U))
 517       S16=0.D0
 518       DO 4 I = 5,12
 519       U=C2*X(I)
 520     4 S16=S16+W(I)*(F(C1+U)+F(C1-U))
 521       S16=C2*S16
 522       IF(ABS(S16-C2*S8) .LE. EPS*(1.D0+ABS(S16))) THEN
 523        H=H+S16
 524        IF(BB .NE. B) GO TO 1
 525       ELSE
 526        BB=C1
 527        IF(1.D0+CONST*ABS(C2) .NE. 1.D0) GO TO 2
 528        H=0.D0
 529        WRITE(6,*) 'DGAUSS1: TOO HIGH ACCURACY REQUIRED'
 530        GO TO 99
 531       END IF
 532    99 DGAUSS1=H
 533       RETURN
 534       END
 535 c
 536       FUNCTION SIMDIS(Numb,zmin,nzur,RI)
 537 C     IT SIMULATES A RANDOM NUMBER ACCORDING TO A DISCRETE DISTRIBUTION GIVEN
 538 C     BY ARRAY YA AT POINTS XA. THOUGHT FOR PYTHIA (PYR(0)).
 539 C     N: NUMBER OF POINTS IN THE ARRAYS.
 540 C     XA: ARRAY OF X-VALUES.
 541 C     YA: ARRAY OF Y-VALUES.
 542 c     RI: VALUE OF THE INTEGRAL.
 543       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
 544       DIMENSION XA(500), YA(500)
 545       common/qpc1/eee,qhatl,omegac
 546       dlz=(1.d0-2.d0*zmin)/500.d0
 547       do 1000 no=1,500
 548       xa(no)=zmin+no*dlz
 549       if(nzur.eq.1) ya(no)=splitq2(xa(no))
 550       if(nzur.eq.21) ya(no)=splitg2(xa(no))
 551       if(nzur.eq.3) ya(no)=splitqqbar(xa(no))
 552  1000 continue
 553       RAL=PYR(0)*RI
 554       XAUX=0.D0
 555       xauxold=0.d0
 556       DO 1001 I=2, Numb, 1
 557       XAUX=XAUX+(XA(I)-XA(I-1))*0.5D0*
 558      + (YA(I)+YA(I-1))
 559
 560            IF (XAUX .GE. RAL) GOTO 2011
 561
 562          IF (I .EQ. Numb) THEN
 563             SIMDIS=XA(I)
 564
 565             RETURN
 566          ENDIF
 567          XAUXOLD=XAUX
 568  1001  CONTINUE
 569  2011  SIMDIS=(XA(I)-XA(I-1))*(RAL-XAUXOLD)/(XAUX-XAUXOLD)+
 570      + XA(I-1)
 571
 572       RETURN
 573       END
 574
 575
 576       SUBROUTINE QPYROBO(XI,YI,ZI,TI,THE,PHI,BEX,BEY,BEZ,XP,YP,ZP,TP)
 577 C     N. Armesto, 16.04.2009
 578 C     performs a boost and rotation of (t,x,y,z) to (tp,xp,yp,zp):
 579 C     cut version of PYROBO, angles and boost parameters identical.
 580       IMPLICIT DOUBLE PRECISION(A-H, O-Z)
 581 C...Local arrays.
 582       DIMENSION ROT(3,3),VR(3),DV(4)
 583 C
 584       X=XI
 585       Y=YI
 586       Z=ZI
 587       T=TI
 588 C...Rotate, typically from z axis to direction (theta,phi).
 589       IF(THE**2+PHI**2.GT.1D-20) THEN
 590         ROT(1,1)=COS(THE)*COS(PHI)
 591         ROT(1,2)=-SIN(PHI)
 592         ROT(1,3)=SIN(THE)*COS(PHI)
 593         ROT(2,1)=COS(THE)*SIN(PHI)
 594         ROT(2,2)=COS(PHI)
 595         ROT(2,3)=SIN(THE)*SIN(PHI)
 596         ROT(3,1)=-SIN(THE)
 597         ROT(3,2)=0D0
 598         ROT(3,3)=COS(THE)
 599 C   Instead of loop 120 in PYROBO.
 600         VR(1)=X
 601         VR(2)=Y
 602         VR(3)=Z
 603 C   Instead of loop 130 in PYROBO.
 604         J=1
 605         X=ROT(J,1)*VR(1)+ROT(J,2)*VR(2)+ROT(J,3)*VR(3)
 606         J=2
 607         Y=ROT(J,1)*VR(1)+ROT(J,2)*VR(2)+ROT(J,3)*VR(3)
 608         J=3
 609         Z=ROT(J,1)*VR(1)+ROT(J,2)*VR(2)+ROT(J,3)*VR(3)
 610       ENDIF
 611 C   If nothing happens...
 612       XP=X
 613       YP=Y
 614       ZP=Z
 615       TP=T
 616 C...Boost, typically from rest to momentum/energy=beta.
 617       IF(BEX**2+BEY**2+BEZ**2.GT.1D-20) THEN
 618         DBX=BEX
 619         DBY=BEY
 620         DBZ=BEZ
 621         DB=SQRT(DBX**2+DBY**2+DBZ**2)
 622         EPS1=1D0-1D-12
 623         IF(DB.GT.EPS1) THEN
 624 C...Rescale boost vector if too close to unity.
 625           CALL PYERRM(3,'(PYROBO:) boost vector too large')
 626           DBX=DBX*(EPS1/DB)
 627           DBY=DBY*(EPS1/DB)
 628           DBZ=DBZ*(EPS1/DB)
 629           DB=EPS1
 630         ENDIF
 631         DGA=1D0/SQRT(1D0-DB**2)
 632 C    Instead of loop 150 in PYROBO.
 633         DV(1)=X
 634         DV(2)=Y
 635         DV(3)=Z
 636         DV(4)=T
 637         DBV=DBX*DV(1)+DBY*DV(2)+DBZ*DV(3)
 638         DGABV=DGA*(DGA*DBV/(1D0+DGA)+DV(4))
 639         XP=DV(1)+DGABV*DBX
 640         YP=DV(2)+DGABV*DBY
 641         ZP=DV(3)+DGABV*DBZ
 642         TP=DGA*(DV(4)+DBV)
 643       ENDIF
 644 C
 645       RETURN
 646       END
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
 657 C
 658 C     PYSHOW ROUTINE FOR Q-PYTHIA version 1.0.
 659 C
 660 C     DATE: 26.09.2008.
 661 C
 662 C     AUTHORS: N. Armesto, L. Cunqueiro and C. A. Salgado
 663 C              Departamento de Fisica de Particulas and IGFAE
 664 C              Universidade de Santiago de Compostela
 665 C              15706 Santiago de Compostela, Spain
 666 C
 667 C     EMAILS: nestor@fpaxp1.usc.es, leticia@fpaxp1.usc.es,
 668 C             Carlos.Salgado@cern.ch
 669 C
 670 C     CONTENT: auxiliary files for modified PYSHOW, fixed to PYTHIA-6.4.18.
 671 C
 672 C     WHEN USING Q-PYTHIA, PLEASE QUOTE:
 673 C
 674 C     1) N. Armesto, G. Corcella, L. Cunqueiro and C. A. Salgado,
 675 C        in preparation.
 676 C     2) T. Sjostrand, S. Mrenna and P. Skands,
 677 C        ``PYTHIA 6.4 physics and manual,''
 678 C        JHEP 0605 (2006) 026 [arXiv:hep-ph/0603175].
 679 C
 680 C     INSTRUCTIONS: initial parton position is initialized by a call
 681 C                   to user-defined routine qpygin(x0,y0,z0,t0),
 682 C                   where these are the initial coordinates in the
 683 C                   center-of-mass frame of the hard collision
 684 C                   (if applicable for the type of process you study).
 685 C                   The values of qhatL and omegac have to be computed
 686 C                   by the user, using his preferred medium model, in
 687 C                   routine qpygeo, which takes as input the position
 688 C                   x,y,z,t of the parton to branch, the trajectory
 689 C                   defined by the three-vector betax,betay,betaz,
 690 C                   (all values in the center-of-mass frame of the
 691 C                   hard collision), and  returns the value of qhatL
 692 C                   (in GeV**2) and omegac (in GeV).
 693 C                   Both routines are to be found at the end of this file.
 694 C
 695 C     DISCLAIMER: this program comes without any guarantees. Beware of
 696 C                 errors and use common sense when interpreting results.
 697 C                 Any modifications are done under exclusive
 698 C                 maker's resposibility.
 699 C
 700 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
 701 C*********************************************************************
 702
 703 C...PYSHOW
 704 C...Generates timelike parton showers from given partons.
 705
 706       SUBROUTINE PYSHOWQ(IP1,IP2,QMAX)
 707
 708 C...Double precision and integer declarations.
 709       IMPLICIT DOUBLE PRECISION(A-H, O-Z)
 710       IMPLICIT INTEGER(I-N)
 711       INTEGER PYK,PYCHGE,PYCOMP
 712 C...Parameter statement to help give large particle numbers.
 713       PARAMETER (KSUSY1=1000000,KSUSY2=2000000,KTECHN=3000000,
 714      &KEXCIT=4000000,KDIMEN=5000000)
 715       PARAMETER (MAXNUR=500)
 716 Cacs+
 717       PARAMETER (NNPOS=4000)
 718       DIMENSION PPOS(NNPOS,4)
 719 Cacs-
 720 C...Commonblocks.
 721       COMMON/PYPART/NPART,NPARTD,IPART(MAXNUR),PTPART(MAXNUR)
 722       COMMON/PYJETS/N,NPAD,K(4000,5),P(4000,5),V(4000,5)
 723       COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
 724       COMMON/PYDAT2/KCHG(500,4),PMAS(500,4),PARF(2000),VCKM(4,4)
 725       COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
 726       COMMON/PYINT1/MINT(400),VINT(400)
 727       SAVE /PYPART/,/PYJETS/,/PYDAT1/,/PYDAT2/,/PYPARS/,/PYINT1/
 728
 729 Cacs+
 730       common/qpc1/eee,qhatl,omegac
 731       common/qpvir1/pmed
 732       common/qpvir2/virt
 733       COMMON/QPLT/QPLTA1,QPLTA2,QPLTBX,QPLTBY,QPLTBZ
 734       external splitg1
 735       external splitq1
 736       external splitg2
 737       external splitq2
 738       external splitqqbar
 739       data iflag/0/
 740 Cacs-
 741 C...Local arrays.
 742       DIMENSION PMTH(5,140),PS(5),PMA(100),PMSD(100),IEP(100),IPA(100),
 743      &KFLA(100),KFLD(100),KFL(100),ITRY(100),ISI(100),ISL(100),DP(100),
 744      &DPT(5,4),KSH(0:140),KCII(2),NIIS(2),IIIS(2,2),THEIIS(2,2),
 745      &PHIIIS(2,2),ISII(2),ISSET(2),ISCOL(0:140),ISCHG(0:140),
 746      &IREF(1000)
 747 Cacs+
 748
 749       IF (IFLAG .EQ. 0) THEN
 750          WRITE(MSTU(11),*)
 751          WRITE(MSTU(11),*) '*******************************************'
 752          WRITE(MSTU(11),*)
 753          WRITE(MSTU(11),*) '            Q-PYTHIA version 1.0'
 754          WRITE(MSTU(11),*)
 755          WRITE(MSTU(11),*) 'DATE: 26.09.2008'
 756          WRITE(MSTU(11),*)
 757          WRITE(MSTU(11),*) 'AUTHORS: N. Armesto, L. Cunqueiro and'
 758          WRITE(MSTU(11),*) '         C. A. Salgado'
 759          WRITE(MSTU(11),*) ' Departamento de Fisica de Particulas'
 760          WRITE(MSTU(11),*) ' and IGFAE'
 761          WRITE(MSTU(11),*) ' Universidade de Santiago de Compostela'
 762          WRITE(MSTU(11),*) ' 15706 Santiago de Compostela, Spain'
 763          WRITE(MSTU(11),*)
 764          WRITE(MSTU(11),*) 'EMAILS: nestor@fpaxp1.usc.es,'
 765          WRITE(MSTU(11),*) '        leticia@fpaxp1.usc.es,'
 766          WRITE(MSTU(11),*) '        Carlos.Salgado@cern.ch'
 767          WRITE(MSTU(11),*)
 768          WRITE(MSTU(11),*) 'NOTE: fixed to PYTHIA-6.4.18'
 769          WRITE(MSTU(11),*)
 770          WRITE(MSTU(11),*) 'WHEN USING Q-PYTHIA, PLEASE QUOTE:'
 771          WRITE(MSTU(11),*) '1) N. Armesto, G. Corcella, L. Cunqueiro'
 772          WRITE(MSTU(11),*) '   and C. A. Salgado, in preparation.'
 773          WRITE(MSTU(11),*) '2) T. Sjostrand, S. Mrenna and P. Skands,'
 774          WRITE(MSTU(11),*) '   PYTHIA 6.4 physics and manual,'
 775          WRITE(MSTU(11),*) '   JHEP 0605 (2006) 026'
 776          WRITE(MSTU(11),*) '   [arXiv:hep-ph/0603175].'
 777          WRITE(MSTU(11),*)
 778          WRITE(MSTU(11),*) 'INSTRUCTIONS: look at the web page and'
 779          WRITE(MSTU(11),*) ' header of modfied routine PYSHOW at the'
 780          WRITE(MSTU(11),*) ' end of Q-PYTHIA file.'
 781          WRITE(MSTU(11),*)
 782          WRITE(MSTU(11),*) 'DISCLAIMER: this program comes without any'
 783          WRITE(MSTU(11),*) ' guarantees. Beware of errors and use'
 784          WRITE(MSTU(11),*) ' common sense when interpreting results.'
 785          WRITE(MSTU(11),*) ' Any modifications are done under exclusive'
 786          WRITE(MSTU(11),*) ' makers resposibility.'
 787          WRITE(MSTU(11),*)
 788          WRITE(MSTU(11),*) '*******************************************'
 789          WRITE(MSTU(11),*)
 790          IFLAG=1
 791       ENDIF
 792 Cacs-
 793
 794 C...Check that QMAX not too low.
 795       IF(MSTJ(41).LE.0) THEN
 796         RETURN
 797       ELSEIF(MSTJ(41).EQ.1.OR.MSTJ(41).EQ.11) THEN
 798         IF(QMAX.LE.PARJ(82).AND.IP2.GE.-80) RETURN
 799       ELSE
 800         IF(QMAX.LE.MIN(PARJ(82),PARJ(83),PARJ(90)).AND.IP2.GE.-80)
 801      &  RETURN
 802       ENDIF
 803
 804 C...Store positions of shower initiating partons.
 805       MPSPD=0
 806       IF(IP1.GT.0.AND.IP1.LE.MIN(N,MSTU(4)-MSTU(32)).AND.IP2.EQ.0) THEN
 807         NPA=1
 808         IPA(1)=IP1
 809       ELSEIF(MIN(IP1,IP2).GT.0.AND.MAX(IP1,IP2).LE.MIN(N,MSTU(4)-
 810      &  MSTU(32))) THEN
 811         NPA=2
 812         IPA(1)=IP1
 813         IPA(2)=IP2
 814       ELSEIF(IP1.GT.0.AND.IP1.LE.MIN(N,MSTU(4)-MSTU(32)).AND.IP2.LT.0
 815      &  .AND.IP2.GE.-80) THEN
 816         NPA=IABS(IP2)
 817         DO 100 I=1,NPA
 818           IPA(I)=IP1+I-1
 819   100   CONTINUE
 820       ELSEIF(IP1.GT.0.AND.IP1.LE.MIN(N,MSTU(4)-MSTU(32)).AND.
 821      &IP2.EQ.-100) THEN
 822         MPSPD=1
 823         NPA=2
 824         IPA(1)=IP1+6
 825         IPA(2)=IP1+7
 826       ELSE
 827         CALL PYERRM(12,
 828      &  '(PYSHOW:) failed to reconstruct showering system')
 829         IF(MSTU(21).GE.1) RETURN
 830       ENDIF
 831
 832 C...Send off to PYPTFS for pT-ordered evolution if requested,
 833 C...if at least 2 partons, and without predefined shower branchings.
 834       IF((MSTJ(41).EQ.11.OR.MSTJ(41).EQ.12).AND.NPA.GE.2.AND.
 835      &MPSPD.EQ.0) THEN
 836         NPART=NPA
 837         DO 110 II=1,NPART
 838           IPART(II)=IPA(II)
 839           PTPART(II)=0.5D0*QMAX
 840   110   CONTINUE
 841         CALL PYPTFS(2,0.5D0*QMAX,0D0,PTGEN)
 842         RETURN
 843       ENDIF
 844
 845 C...Initialization of cutoff masses etc.
 846       DO 120 IFL=0,40
 847         ISCOL(IFL)=0
 848         ISCHG(IFL)=0
 849         KSH(IFL)=0
 850   120 CONTINUE
 851       ISCOL(21)=1
 852       KSH(21)=1
 853       PMTH(1,21)=PYMASS(21)
 854       PMTH(2,21)=SQRT(PMTH(1,21)**2+0.25D0*PARJ(82)**2)
 855       PMTH(3,21)=2D0*PMTH(2,21)
 856       PMTH(4,21)=PMTH(3,21)
 857       PMTH(5,21)=PMTH(3,21)
 858       PMTH(1,22)=PYMASS(22)
 859       PMTH(2,22)=SQRT(PMTH(1,22)**2+0.25D0*PARJ(83)**2)
 860       PMTH(3,22)=2D0*PMTH(2,22)
 861       PMTH(4,22)=PMTH(3,22)
 862       PMTH(5,22)=PMTH(3,22)
 863       PMQTH1=PARJ(82)
 864       IF(MSTJ(41).GE.2) PMQTH1=MIN(PARJ(82),PARJ(83))
 865       PMQT1E=MIN(PMQTH1,PARJ(90))
 866       PMQTH2=PMTH(2,21)
 867       IF(MSTJ(41).GE.2) PMQTH2=MIN(PMTH(2,21),PMTH(2,22))
 868       PMQT2E=MIN(PMQTH2,0.5D0*PARJ(90))
 869       DO 130 IFL=1,5
 870         ISCOL(IFL)=1
 871         IF(MSTJ(41).GE.2) ISCHG(IFL)=1
 872         KSH(IFL)=1
 873         PMTH(1,IFL)=PYMASS(IFL)
 874         PMTH(2,IFL)=SQRT(PMTH(1,IFL)**2+0.25D0*PMQTH1**2)
 875         PMTH(3,IFL)=PMTH(2,IFL)+PMQTH2
 876         PMTH(4,IFL)=SQRT(PMTH(1,IFL)**2+0.25D0*PARJ(82)**2)+PMTH(2,21)
 877         PMTH(5,IFL)=SQRT(PMTH(1,IFL)**2+0.25D0*PARJ(83)**2)+PMTH(2,22)
 878   130 CONTINUE
 879       DO 140 IFL=11,15,2
 880         IF(MSTJ(41).EQ.2.OR.MSTJ(41).GE.4) ISCHG(IFL)=1
 881         IF(MSTJ(41).EQ.2.OR.MSTJ(41).GE.4) KSH(IFL)=1
 882         PMTH(1,IFL)=PYMASS(IFL)
 883         PMTH(2,IFL)=SQRT(PMTH(1,IFL)**2+0.25D0*PARJ(90)**2)
 884         PMTH(3,IFL)=PMTH(2,IFL)+0.5D0*PARJ(90)
 885         PMTH(4,IFL)=PMTH(3,IFL)
 886         PMTH(5,IFL)=PMTH(3,IFL)
 887   140 CONTINUE
 888       PT2MIN=MAX(0.5D0*PARJ(82),1.1D0*PARJ(81))**2
 889       ALAMS=PARJ(81)**2
 890       ALFM=LOG(PT2MIN/ALAMS)
 891
 892 C...Check on phase space available for emission.
 893       IREJ=0
 894       DO 150 J=1,5
 895         PS(J)=0D0
 896   150 CONTINUE
 897       PM=0D0
 898       KFLA(2)=0
 899       DO 170 I=1,NPA
 900         KFLA(I)=IABS(K(IPA(I),2))
 901         PMA(I)=P(IPA(I),5)
 902 C...Special cutoff masses for initial partons (may be a heavy quark,
 903 C...squark, ..., and need not be on the mass shell).
 904         IR=30+I
 905         IF(NPA.LE.1) IREF(I)=IR
 906         IF(NPA.GE.2) IREF(I+1)=IR
 907         ISCOL(IR)=0
 908         ISCHG(IR)=0
 909         KSH(IR)=0
 910         IF(KFLA(I).LE.8) THEN
 911           ISCOL(IR)=1
 912           IF(MSTJ(41).GE.2) ISCHG(IR)=1
 913         ELSEIF(KFLA(I).EQ.11.OR.KFLA(I).EQ.13.OR.KFLA(I).EQ.15.OR.
 914      &  KFLA(I).EQ.17) THEN
 915           IF(MSTJ(41).EQ.2.OR.MSTJ(41).GE.4) ISCHG(IR)=1
 916         ELSEIF(KFLA(I).EQ.21) THEN
 917           ISCOL(IR)=1
 918         ELSEIF((KFLA(I).GE.KSUSY1+1.AND.KFLA(I).LE.KSUSY1+8).OR.
 919      &  (KFLA(I).GE.KSUSY2+1.AND.KFLA(I).LE.KSUSY2+8)) THEN
 920           ISCOL(IR)=1
 921         ELSEIF(KFLA(I).EQ.KSUSY1+21) THEN
 922           ISCOL(IR)=1
 923 C...QUARKONIA+++
 924 C...same for QQ~[3S18]
 925         ELSEIF(MSTP(148).GE.1.AND.(KFLA(I).EQ.9900443.OR.
 926      &  KFLA(I).EQ.9900553)) THEN
 927           ISCOL(IR)=1
 928 C...QUARKONIA---
 929         ENDIF
 930         IF(ISCOL(IR).EQ.1.OR.ISCHG(IR).EQ.1) KSH(IR)=1
 931         PMTH(1,IR)=PMA(I)
 932         IF(ISCOL(IR).EQ.1.AND.ISCHG(IR).EQ.1) THEN
 933           PMTH(2,IR)=SQRT(PMTH(1,IR)**2+0.25D0*PMQTH1**2)
 934           PMTH(3,IR)=PMTH(2,IR)+PMQTH2
 935           PMTH(4,IR)=SQRT(PMTH(1,IR)**2+0.25D0*PARJ(82)**2)+PMTH(2,21)
 936           PMTH(5,IR)=SQRT(PMTH(1,IR)**2+0.25D0*PARJ(83)**2)+PMTH(2,22)
 937         ELSEIF(ISCOL(IR).EQ.1) THEN
 938           PMTH(2,IR)=SQRT(PMTH(1,IR)**2+0.25D0*PARJ(82)**2)
 939           PMTH(3,IR)=PMTH(2,IR)+0.5D0*PARJ(82)
 940           PMTH(4,IR)=PMTH(3,IR)
 941           PMTH(5,IR)=PMTH(3,IR)
 942         ELSEIF(ISCHG(IR).EQ.1) THEN
 943           PMTH(2,IR)=SQRT(PMTH(1,IR)**2+0.25D0*PARJ(90)**2)
 944           PMTH(3,IR)=PMTH(2,IR)+0.5D0*PARJ(90)
 945           PMTH(4,IR)=PMTH(3,IR)
 946           PMTH(5,IR)=PMTH(3,IR)
 947         ENDIF
 948         IF(KSH(IR).EQ.1) PMA(I)=PMTH(3,IR)
 949         PM=PM+PMA(I)
 950         IF(KSH(IR).EQ.0.OR.PMA(I).GT.10D0*QMAX) IREJ=IREJ+1
 951         DO 160 J=1,4
 952           PS(J)=PS(J)+P(IPA(I),J)
 953   160   CONTINUE
 954   170 CONTINUE
 955       IF(IREJ.EQ.NPA.AND.IP2.GE.-7) RETURN
 956       PS(5)=SQRT(MAX(0D0,PS(4)**2-PS(1)**2-PS(2)**2-PS(3)**2))
 957       IF(NPA.EQ.1) PS(5)=PS(4)
 958       IF(PS(5).LE.PM+PMQT1E) RETURN
 959
 960 C...Identify source: q(1), ~q(2), V(3), S(4), chi(5), ~g(6), unknown(0).
 961       KFSRCE=0
 962       IF(IP2.LE.0) THEN
 963       ELSEIF(K(IP1,3).EQ.K(IP2,3).AND.K(IP1,3).GT.0) THEN
 964         KFSRCE=IABS(K(K(IP1,3),2))
 965       ELSE
 966         IPAR1=MAX(1,K(IP1,3))
 967         IPAR2=MAX(1,K(IP2,3))
 968         IF(K(IPAR1,3).EQ.K(IPAR2,3).AND.K(IPAR1,3).GT.0)
 969      &       KFSRCE=IABS(K(K(IPAR1,3),2))
 970       ENDIF
 971       ITYPES=0
 972       IF(KFSRCE.GE.1.AND.KFSRCE.LE.8) ITYPES=1
 973       IF(KFSRCE.GE.KSUSY1+1.AND.KFSRCE.LE.KSUSY1+8) ITYPES=2
 974       IF(KFSRCE.GE.KSUSY2+1.AND.KFSRCE.LE.KSUSY2+8) ITYPES=2
 975       IF(KFSRCE.GE.21.AND.KFSRCE.LE.24) ITYPES=3
 976       IF(KFSRCE.GE.32.AND.KFSRCE.LE.34) ITYPES=3
 977       IF(KFSRCE.EQ.25.OR.(KFSRCE.GE.35.AND.KFSRCE.LE.37)) ITYPES=4
 978       IF(KFSRCE.GE.KSUSY1+22.AND.KFSRCE.LE.KSUSY1+37) ITYPES=5
 979       IF(KFSRCE.EQ.KSUSY1+21) ITYPES=6
 980
 981 C...Identify two primary showerers.
 982       ITYPE1=0
 983       IF(KFLA(1).GE.1.AND.KFLA(1).LE.8) ITYPE1=1
 984       IF(KFLA(1).GE.KSUSY1+1.AND.KFLA(1).LE.KSUSY1+8) ITYPE1=2
 985       IF(KFLA(1).GE.KSUSY2+1.AND.KFLA(1).LE.KSUSY2+8) ITYPE1=2
 986       IF(KFLA(1).GE.21.AND.KFLA(1).LE.24) ITYPE1=3
 987       IF(KFLA(1).GE.32.AND.KFLA(1).LE.34) ITYPE1=3
 988       IF(KFLA(1).EQ.25.OR.(KFLA(1).GE.35.AND.KFLA(1).LE.37)) ITYPE1=4
 989       IF(KFLA(1).GE.KSUSY1+22.AND.KFLA(1).LE.KSUSY1+37) ITYPE1=5
 990       IF(KFLA(1).EQ.KSUSY1+21) ITYPE1=6
 991       ITYPE2=0
 992       IF(KFLA(2).GE.1.AND.KFLA(2).LE.8) ITYPE2=1
 993       IF(KFLA(2).GE.KSUSY1+1.AND.KFLA(2).LE.KSUSY1+8) ITYPE2=2
 994       IF(KFLA(2).GE.KSUSY2+1.AND.KFLA(2).LE.KSUSY2+8) ITYPE2=2
 995       IF(KFLA(2).GE.21.AND.KFLA(2).LE.24) ITYPE2=3
 996       IF(KFLA(2).GE.32.AND.KFLA(2).LE.34) ITYPE2=3
 997       IF(KFLA(2).EQ.25.OR.(KFLA(2).GE.35.AND.KFLA(2).LE.37)) ITYPE2=4
 998       IF(KFLA(2).GE.KSUSY1+22.AND.KFLA(2).LE.KSUSY1+37) ITYPE2=5
 999       IF(KFLA(2).EQ.KSUSY1+21) ITYPE2=6
1000
1001 C...Order of showerers. Presence of gluino.
1002       ITYPMN=MIN(ITYPE1,ITYPE2)
1003       ITYPMX=MAX(ITYPE1,ITYPE2)
1004       IORD=1
1005       IF(ITYPE1.GT.ITYPE2) IORD=2
1006       IGLUI=0
1007       IF(ITYPE1.EQ.6.OR.ITYPE2.EQ.6) IGLUI=1
1008
1009 C...Check if 3-jet matrix elements to be used.
1010       M3JC=0
1011       ALPHA=0.5D0
1012       IF(NPA.EQ.2.AND.MSTJ(47).GE.1.AND.MPSPD.EQ.0) THEN
1013         IF(MSTJ(38).NE.0) THEN
1014           M3JC=MSTJ(38)
1015           ALPHA=PARJ(80)
1016           MSTJ(38)=0
1017         ELSEIF(MSTJ(47).GE.6) THEN
1018           M3JC=MSTJ(47)
1019         ELSE
1020           ICLASS=1
1021           ICOMBI=4
1022
1023 C...Vector/axial vector -> q + qbar; q -> q + V.
1024           IF(ITYPMN.EQ.1.AND.ITYPMX.EQ.1.AND.(ITYPES.EQ.0.OR.
1025      &    ITYPES.EQ.3)) THEN
1026             ICLASS=2
1027             IF(KFSRCE.EQ.21.OR.KFSRCE.EQ.22) THEN
1028               ICOMBI=1
1029             ELSEIF(KFSRCE.EQ.23.OR.(KFSRCE.EQ.0.AND.
1030      &      K(IPA(1),2)+K(IPA(2),2).EQ.0)) THEN
1031 C...gamma*/Z0: assume e+e- initial state if unknown.
1032               EI=-1D0
1033               IF(KFSRCE.EQ.23) THEN
1034                 IANNFL=K(K(IP1,3),3)
1035                 IF(IANNFL.NE.0) THEN
1036                   KANNFL=IABS(K(IANNFL,2))
1037                   IF(KANNFL.GE.1.AND.KANNFL.LE.18) EI=KCHG(KANNFL,1)/3D0
1038                 ENDIF
1039               ENDIF
1040               AI=SIGN(1D0,EI+0.1D0)
1041               VI=AI-4D0*EI*PARU(102)
1042               EF=KCHG(KFLA(1),1)/3D0
1043               AF=SIGN(1D0,EF+0.1D0)
1044               VF=AF-4D0*EF*PARU(102)
1045               XWC=1D0/(16D0*PARU(102)*(1D0-PARU(102)))
1046               SH=PS(5)**2
1047               SQMZ=PMAS(23,1)**2
1048               SQWZ=PS(5)*PMAS(23,2)
1049               SBWZ=1D0/((SH-SQMZ)**2+SQWZ**2)
1050               VECT=EI**2*EF**2+2D0*EI*VI*EF*VF*XWC*SH*(SH-SQMZ)*SBWZ+
1051      &        (VI**2+AI**2)*VF**2*XWC**2*SH**2*SBWZ
1052               AXIV=(VI**2+AI**2)*AF**2*XWC**2*SH**2*SBWZ
1053               ICOMBI=3
1054               ALPHA=VECT/(VECT+AXIV)
1055             ELSEIF(KFSRCE.EQ.24.OR.KFSRCE.EQ.0) THEN
1056               ICOMBI=4
1057             ENDIF
1058 C...For chi -> chi q qbar, use V/A -> q qbar as first approximation.
1059           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.1.AND.ITYPES.EQ.5) THEN
1060             ICLASS=2
1061           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.3.AND.(ITYPES.EQ.0.OR.
1062      &    ITYPES.EQ.1)) THEN
1063             ICLASS=3
1064
1065 C...Scalar/pseudoscalar -> q + qbar; q -> q + S.
1066           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.1.AND.ITYPES.EQ.4) THEN
1067             ICLASS=4
1068             IF(KFSRCE.EQ.25.OR.KFSRCE.EQ.35.OR.KFSRCE.EQ.37) THEN
1069               ICOMBI=1
1070             ELSEIF(KFSRCE.EQ.36) THEN
1071               ICOMBI=2
1072             ENDIF
1073           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.4.AND.(ITYPES.EQ.0.OR.
1074      &    ITYPES.EQ.1)) THEN
1075             ICLASS=5
1076
1077 C...V -> ~q + ~qbar; ~q -> ~q + V; S -> ~q + ~qbar; ~q -> ~q + S.
1078           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.2.AND.(ITYPES.EQ.0.OR.
1079      &    ITYPES.EQ.3)) THEN
1080             ICLASS=6
1081           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.3.AND.(ITYPES.EQ.0.OR.
1082      &    ITYPES.EQ.2)) THEN
1083             ICLASS=7
1084           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.2.AND.ITYPES.EQ.4) THEN
1085             ICLASS=8
1086           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.4.AND.(ITYPES.EQ.0.OR.
1087      &    ITYPES.EQ.2)) THEN
1088             ICLASS=9
1089
1090 C...chi -> q + ~qbar; ~q -> q + chi; q -> ~q + chi.
1091           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.2.AND.(ITYPES.EQ.0.OR.
1092      &    ITYPES.EQ.5)) THEN
1093             ICLASS=10
1094           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.5.AND.(ITYPES.EQ.0.OR.
1095      &    ITYPES.EQ.2)) THEN
1096             ICLASS=11
1097           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.5.AND.(ITYPES.EQ.0.OR.
1098      &    ITYPES.EQ.1)) THEN
1099             ICLASS=12
1100
1101 C...~g -> q + ~qbar; ~q -> q + ~g; q -> ~q + ~g.
1102           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.2.AND.ITYPES.EQ.6) THEN
1103             ICLASS=13
1104           ELSEIF(ITYPMN.EQ.1.AND.ITYPMX.EQ.6.AND.(ITYPES.EQ.0.OR.
1105      &    ITYPES.EQ.2)) THEN
1106             ICLASS=14
1107           ELSEIF(ITYPMN.EQ.2.AND.ITYPMX.EQ.6.AND.(ITYPES.EQ.0.OR.
1108      &    ITYPES.EQ.1)) THEN
1109             ICLASS=15
1110
1111 C...g -> ~g + ~g (eikonal approximation).
1112           ELSEIF(ITYPMN.EQ.6.AND.ITYPMX.EQ.6.AND.ITYPES.EQ.0) THEN
1113             ICLASS=16
1114           ENDIF
1115           M3JC=5*ICLASS+ICOMBI
1116         ENDIF
1117       ENDIF
1118
1119 C...Find if interference with initial state partons.
1120       MIIS=0
1121       IF(MSTJ(50).GE.1.AND.MSTJ(50).LE.3.AND.NPA.EQ.2.AND.KFSRCE.EQ.0
1122      &.AND.MPSPD.EQ.0) MIIS=MSTJ(50)
1123       IF(MSTJ(50).GE.4.AND.MSTJ(50).LE.6.AND.NPA.EQ.2.AND.MPSPD.EQ.0)
1124      &MIIS=MSTJ(50)-3
1125       IF(MIIS.NE.0) THEN
1126         DO 190 I=1,2
1127           KCII(I)=0
1128           KCA=PYCOMP(KFLA(I))
1129           IF(KCA.NE.0) KCII(I)=KCHG(KCA,2)*ISIGN(1,K(IPA(I),2))
1130           NIIS(I)=0
1131           IF(KCII(I).NE.0) THEN
1132             DO 180 J=1,2
1133               ICSI=MOD(K(IPA(I),3+J)/MSTU(5),MSTU(5))
1134               IF(ICSI.GT.0.AND.ICSI.NE.IPA(1).AND.ICSI.NE.IPA(2).AND.
1135      &        (KCII(I).EQ.(-1)**(J+1).OR.KCII(I).EQ.2)) THEN
1136                 NIIS(I)=NIIS(I)+1
1137                 IIIS(I,NIIS(I))=ICSI
1138               ENDIF
1139   180       CONTINUE
1140           ENDIF
1141   190   CONTINUE
1142         IF(NIIS(1)+NIIS(2).EQ.0) MIIS=0
1143       ENDIF
1144
1145 C...Boost interfering initial partons to rest frame
1146 C...and reconstruct their polar and azimuthal angles.
1147 Cacs+
1148         qplta1=0.d0
1149         qplta2=0.d0
1150         qpltbx=0.d0
1151         qpltby=0.d0
1152         qpltbz=0.d0
1153 Cacs-
1154       IF(MIIS.NE.0) THEN
1155         DO 210 I=1,2
1156           DO 200 J=1,5
1157             K(N+I,J)=K(IPA(I),J)
1158             P(N+I,J)=P(IPA(I),J)
1159             V(N+I,J)=0D0
1160   200     CONTINUE
1161   210   CONTINUE
1162         DO 230 I=3,2+NIIS(1)
1163           DO 220 J=1,5
1164             K(N+I,J)=K(IIIS(1,I-2),J)
1165             P(N+I,J)=P(IIIS(1,I-2),J)
1166             V(N+I,J)=0D0
1167   220     CONTINUE
1168   230   CONTINUE
1169         DO 250 I=3+NIIS(1),2+NIIS(1)+NIIS(2)
1170           DO 240 J=1,5
1171             K(N+I,J)=K(IIIS(2,I-2-NIIS(1)),J)
1172             P(N+I,J)=P(IIIS(2,I-2-NIIS(1)),J)
1173             V(N+I,J)=0D0
1174   240     CONTINUE
1175   250   CONTINUE
1176         CALL PYROBO(N+1,N+2+NIIS(1)+NIIS(2),0D0,0D0,-PS(1)/PS(4),
1177      &  -PS(2)/PS(4),-PS(3)/PS(4))
1178         PHI=PYANGL(P(N+1,1),P(N+1,2))
1179         CALL PYROBO(N+1,N+2+NIIS(1)+NIIS(2),0D0,-PHI,0D0,0D0,0D0)
1180         THE=PYANGL(P(N+1,3),P(N+1,1))
1181         CALL PYROBO(N+1,N+2+NIIS(1)+NIIS(2),-THE,0D0,0D0,0D0,0D0)
1182 Cacs+
1183         qplta1=-the
1184         qplta2=-phi
1185         qpltbx=-PS(1)/PS(4)
1186         qpltby=-PS(2)/PS(4)
1187         qpltbz=-PS(3)/PS(4)
1188 Cacs-
1189         DO 260 I=3,2+NIIS(1)
1190           THEIIS(1,I-2)=PYANGL(P(N+I,3),SQRT(P(N+I,1)**2+P(N+I,2)**2))
1191           PHIIIS(1,I-2)=PYANGL(P(N+I,1),P(N+I,2))
1192   260   CONTINUE
1193         DO 270 I=3+NIIS(1),2+NIIS(1)+NIIS(2)
1194           THEIIS(2,I-2-NIIS(1))=PARU(1)-PYANGL(P(N+I,3),
1195      &    SQRT(P(N+I,1)**2+P(N+I,2)**2))
1196           PHIIIS(2,I-2-NIIS(1))=PYANGL(P(N+I,1),P(N+I,2))
1197   270   CONTINUE
1198       ENDIF
1199
1200 C...Boost 3 or more partons to their rest frame.
1201 Cacs+
1202 c      IF(NPA.GE.3) CALL PYROBO(IPA(1),IPA(NPA),0D0,0D0,-PS(1)/PS(4),
1203 c     &-PS(2)/PS(4),-PS(3)/PS(4))
1204       IF(NPA.GE.3) THEN
1205         CALL PYROBO(IPA(1),IPA(NPA),0D0,0D0,-PS(1)/PS(4),
1206      &-PS(2)/PS(4),-PS(3)/PS(4))
1207         qplta1=0.d0
1208         qplta2=0.d0
1209         qpltbx=-PS(1)/PS(4)
1210         qpltby=-PS(2)/PS(4)
1211         qpltbz=-PS(3)/PS(4)
1212
1213       ENDIF
1214 Cacs-
1215
1216 C...Define imagined single initiator of shower for parton system.
1217       NS=N
1218       IF(N.GT.MSTU(4)-MSTU(32)-10) THEN
1219         CALL PYERRM(11,'(PYSHOW:) no more memory left in PYJETS')
1220         IF(MSTU(21).GE.1) RETURN
1221       ENDIF
1222   280 N=NS
1223       IF(NPA.GE.2) THEN
1224         K(N+1,1)=11
1225         K(N+1,2)=21
1226         K(N+1,3)=0
1227         K(N+1,4)=0
1228         K(N+1,5)=0
1229         P(N+1,1)=0D0
1230         P(N+1,2)=0D0
1231         P(N+1,3)=0D0
1232         P(N+1,4)=PS(5)
1233         P(N+1,5)=PS(5)
1234         V(N+1,5)=PS(5)**2
1235         N=N+1
1236         IREF(1)=21
1237       ENDIF
1238
1239
1240
1241
1242 Cacs+
1243       call qpygin(pposx0,pposy0,pposz0,ppost0) ! in fm
1244       do 10101 iijj=1, nnpos, 1
1245          ppos(iijj,1)=pposx0
1246          ppos(iijj,2)=pposy0
1247          ppos(iijj,3)=pposz0
1248          ppos(iijj,4)=ppost0
1249 10101 continue
1250
1251 Cacs-
1252
1253
1254
1255
1256 C...Loop over partons that may branch.
1257       NEP=NPA
1258       IM=NS
1259       IF(NPA.EQ.1) IM=NS-1
1260   290 IM=IM+1
1261       IF(N.GT.NS) THEN
1262         IF(IM.GT.N) GOTO 600
1263         KFLM=IABS(K(IM,2))
1264         IR=IREF(IM-NS)
1265         IF(KSH(IR).EQ.0) GOTO 290
1266         IF(P(IM,5).LT.PMTH(2,IR)) GOTO 290
1267         IGM=K(IM,3)
1268       ELSE
1269         IGM=-1
1270       ENDIF
1271       IF(N+NEP.GT.MSTU(4)-MSTU(32)-10) THEN
1272         CALL PYERRM(11,'(PYSHOW:) no more memory left in PYJETS')
1273         IF(MSTU(21).GE.1) RETURN
1274       ENDIF
1275
1276 C...Position of aunt (sister to branching parton).
1277 C...Origin and flavour of daughters.
1278       IAU=0
1279       IF(IGM.GT.0) THEN
1280         IF(K(IM-1,3).EQ.IGM) IAU=IM-1
1281         IF(N.GE.IM+1.AND.K(IM+1,3).EQ.IGM) IAU=IM+1
1282       ENDIF
1283       IF(IGM.GE.0) THEN
1284         K(IM,4)=N+1
1285         DO 300 I=1,NEP
1286           K(N+I,3)=IM
1287   300   CONTINUE
1288       ELSE
1289         K(N+1,3)=IPA(1)
1290       ENDIF
1291       IF(IGM.LE.0) THEN
1292         DO 310 I=1,NEP
1293           K(N+I,2)=K(IPA(I),2)
1294   310   CONTINUE
1295       ELSEIF(KFLM.NE.21) THEN
1296         K(N+1,2)=K(IM,2)
1297         K(N+2,2)=K(IM,5)
1298         IREF(N+1-NS)=IREF(IM-NS)
1299         IREF(N+2-NS)=IABS(K(N+2,2))
1300       ELSEIF(K(IM,5).EQ.21) THEN
1301         K(N+1,2)=21
1302         K(N+2,2)=21
1303         IREF(N+1-NS)=21
1304         IREF(N+2-NS)=21
1305       ELSE
1306         K(N+1,2)=K(IM,5)
1307         K(N+2,2)=-K(IM,5)
1308         IREF(N+1-NS)=IABS(K(N+1,2))
1309         IREF(N+2-NS)=IABS(K(N+2,2))
1310       ENDIF
1311
1312 C...Reset flags on daughters and tries made.
1313       DO 320 IP=1,NEP
1314         K(N+IP,1)=3
1315         K(N+IP,4)=0
1316         K(N+IP,5)=0
1317         KFLD(IP)=IABS(K(N+IP,2))
1318         IF(KCHG(PYCOMP(KFLD(IP)),2).EQ.0) K(N+IP,1)=1
1319         ITRY(IP)=0
1320         ISL(IP)=0
1321         ISI(IP)=0
1322         IF(KSH(IREF(N+IP-NS)).EQ.1) ISI(IP)=1
1323   320 CONTINUE
1324       ISLM=0
1325
1326 C...Maximum virtuality of daughters.
1327       IF(IGM.LE.0) THEN
1328         DO 330 I=1,NPA
1329           IF(NPA.GE.3) P(N+I,4)=P(IPA(I),4)
1330           P(N+I,5)=MIN(QMAX,PS(5))
1331           IR=IREF(N+I-NS)
1332           IF(IP2.LE.-8) P(N+I,5)=MAX(P(N+I,5),2D0*PMTH(3,IR))
1333           IF(ISI(I).EQ.0) P(N+I,5)=P(IPA(I),5)
1334   330   CONTINUE
1335       ELSE
1336         IF(MSTJ(43).LE.2) PEM=V(IM,2)
1337         IF(MSTJ(43).GE.3) PEM=P(IM,4)
1338         P(N+1,5)=MIN(P(IM,5),V(IM,1)*PEM)
1339         P(N+2,5)=MIN(P(IM,5),(1D0-V(IM,1))*PEM)
1340         IF(K(N+2,2).EQ.22) P(N+2,5)=PMTH(1,22)
1341       ENDIF
1342       DO 340 I=1,NEP
1343         PMSD(I)=P(N+I,5)
1344         IF(ISI(I).EQ.1) THEN
1345           IR=IREF(N+I-NS)
1346           IF(P(N+I,5).LE.PMTH(3,IR)) P(N+I,5)=PMTH(1,IR)
1347         ENDIF
1348         V(N+I,5)=P(N+I,5)**2
1349   340 CONTINUE
1350
1351 C...Choose one of the daughters for evolution.
1352   350 INUM=0
1353       IF(NEP.EQ.1) INUM=1
1354       DO 360 I=1,NEP
1355         IF(INUM.EQ.0.AND.ISL(I).EQ.1) INUM=I
1356   360 CONTINUE
1357       DO 370 I=1,NEP
1358         IF(INUM.EQ.0.AND.ITRY(I).EQ.0.AND.ISI(I).EQ.1) THEN
1359           IR=IREF(N+I-NS)
1360           IF(P(N+I,5).GE.PMTH(2,IR)) INUM=I
1361         ENDIF
1362   370 CONTINUE
1363       IF(INUM.EQ.0) THEN
1364         RMAX=0D0
1365         DO 380 I=1,NEP
1366           IF(ISI(I).EQ.1.AND.PMSD(I).GE.PMQT2E) THEN
1367             RPM=P(N+I,5)/PMSD(I)
1368             IR=IREF(N+I-NS)
1369             IF(RPM.GT.RMAX.AND.P(N+I,5).GE.PMTH(2,IR)) THEN
1370               RMAX=RPM
1371               INUM=I
1372             ENDIF
1373           ENDIF
1374   380   CONTINUE
1375       ENDIF
1376
1377 C...Cancel choice of predetermined daughter already treated.
1378       INUM=MAX(1,INUM)
1379       INUMT=INUM
1380       IF(MPSPD.EQ.1.AND.IGM.EQ.0.AND.ITRY(INUMT).GE.1) THEN
1381         IF(K(IP1-1+INUM,4).GT.0) INUM=3-INUM
1382       ELSEIF(MPSPD.EQ.1.AND.IM.EQ.NS+2.AND.ITRY(INUMT).GE.1) THEN
1383         IF(KFLD(INUMT).NE.21.AND.K(IP1+2,4).GT.0) INUM=3-INUM
1384         IF(KFLD(INUMT).EQ.21.AND.K(IP1+3,4).GT.0) INUM=3-INUM
1385       ENDIF
1386
1387 C...Store information on choice of evolving daughter.
1388       IEP(1)=N+INUM
1389 Cacs+
1390       idf=k(iep(1),3)
1391       zz1=v(idf,1)
1392       zzz=zz1
1393       zz2=1.d0-zz1
1394       if (nep .gt. 1 .and. inum .eq. 2) then
1395          zzz=zz2
1396       endif
1397       ttt=v(idf,5)
1398       if(zz1.gt.0.d0) then
1399             eee=zzz*p(idf,4)
1400       else
1401             eee=p(idf,4)
1402       endif
1403       xkt=zz1*zz2*ttt
1404       if (xkt .gt. 0.d0) then
1405          xlcoh=(2.d0*eee/(zz1*zz2*ttt))*0.1973d0
1406       else
1407          xlcoh=0.d0
1408       endif
1409       if (idf .eq. 0) then ! for the initial parton if it has no father
1410          xbx=p(iep(1),1)/p(iep(1),4)
1411          xby=p(iep(1),2)/p(iep(1),4)
1412          xbz=p(iep(1),3)/p(iep(1),4)
1413          call qpygeo(pposx0,pposy0,pposz0,ppost0,
1414      >               xbx,xby,xbz,qhatl,omegac)
1415       else
1416          xbx=p(idf,1)/p(idf,4)
1417          xby=p(idf,2)/p(idf,4)
1418          xbz=p(idf,3)/p(idf,4)
1419
1420
1421
1422          ppos(iep(1),1)=ppos(idf,1)+xbx*xlcoh
1423          ppos(iep(1),2)=ppos(idf,2)+xby*xlcoh
1424          ppos(iep(1),3)=ppos(idf,3)+xbz*xlcoh
1425          ppos(iep(1),4)=ppos(idf,4)+xlcoh
1426          call qpygeo(ppos(iep(1),1),ppos(iep(1),2),ppos(iep(1),3),
1427      >               ppos(iep(1),4),xbx,xby,xbz,qhatl,omegac)
1428       endif
1429 Cacs-
1430
1431       DO 390 I=2,NEP
1432         IEP(I)=IEP(I-1)+1
1433         IF(IEP(I).GT.N+NEP) IEP(I)=N+1
1434   390 CONTINUE
1435       DO 400 I=1,NEP
1436         KFL(I)=IABS(K(IEP(I),2))
1437   400 CONTINUE
1438       ITRY(INUM)=ITRY(INUM)+1
1439       IF(ITRY(INUM).GT.200) THEN
1440         CALL PYERRM(14,'(PYSHOW:) caught in infinite loop')
1441         IF(MSTU(21).GE.1) RETURN
1442       ENDIF
1443       Z=0.5D0
1444       IR=IREF(IEP(1)-NS)
1445       IF(KSH(IR).EQ.0) GOTO 450
1446       IF(P(IEP(1),5).LT.PMTH(2,IR)) GOTO 450
1447
1448 C...Check if evolution already predetermined for daughter.
1449       IPSPD=0
1450       IF(MPSPD.EQ.1.AND.IGM.EQ.0) THEN
1451         IF(K(IP1-1+INUM,4).GT.0) IPSPD=IP1-1+INUM
1452       ELSEIF(MPSPD.EQ.1.AND.IM.EQ.NS+2) THEN
1453         IF(KFL(1).NE.21.AND.K(IP1+2,4).GT.0) IPSPD=IP1+2
1454         IF(KFL(1).EQ.21.AND.K(IP1+3,4).GT.0) IPSPD=IP1+3
1455       ENDIF
1456       IF(INUM.EQ.1.OR.INUM.EQ.2) THEN
1457         ISSET(INUM)=0
1458         IF(IPSPD.NE.0) ISSET(INUM)=1
1459       ENDIF
1460
1461 C...Select side for interference with initial state partons.
1462       IF(MIIS.GE.1.AND.IEP(1).LE.NS+3) THEN
1463         III=IEP(1)-NS-1
1464         ISII(III)=0
1465         IF(IABS(KCII(III)).EQ.1.AND.NIIS(III).EQ.1) THEN
1466           ISII(III)=1
1467         ELSEIF(KCII(III).EQ.2.AND.NIIS(III).EQ.1) THEN
1468           IF(PYR(0).GT.0.5D0) ISII(III)=1
1469         ELSEIF(KCII(III).EQ.2.AND.NIIS(III).EQ.2) THEN
1470           ISII(III)=1
1471           IF(PYR(0).GT.0.5D0) ISII(III)=2
1472         ENDIF
1473       ENDIF
1474
1475 C...Calculate allowed z range.
1476       IF(NEP.EQ.1) THEN
1477         PMED=PS(4)
1478       ELSEIF(IGM.EQ.0.OR.MSTJ(43).LE.2) THEN
1479         PMED=P(IM,5)
1480       ELSE
1481         IF(INUM.EQ.1) PMED=V(IM,1)*PEM
1482         IF(INUM.EQ.2) PMED=(1D0-V(IM,1))*PEM
1483       ENDIF
1484       IF(MOD(MSTJ(43),2).EQ.1) THEN
1485         ZC=PMTH(2,21)/PMED
1486         ZCE=PMTH(2,22)/PMED
1487         IF(ISCOL(IR).EQ.0) ZCE=0.5D0*PARJ(90)/PMED
1488       ELSE
1489         ZC=0.5D0*(1D0-SQRT(MAX(0D0,1D0-(2D0*PMTH(2,21)/PMED)**2)))
1490         IF(ZC.LT.1D-6) ZC=(PMTH(2,21)/PMED)**2
1491         PMTMPE=PMTH(2,22)
1492         IF(ISCOL(IR).EQ.0) PMTMPE=0.5D0*PARJ(90)
1493         ZCE=0.5D0*(1D0-SQRT(MAX(0D0,1D0-(2D0*PMTMPE/PMED)**2)))
1494         IF(ZCE.LT.1D-6) ZCE=(PMTMPE/PMED)**2
1495       ENDIF
1496       ZC=MIN(ZC,0.491D0)
1497       ZCE=MIN(ZCE,0.49991D0)
1498       IF(((MSTJ(41).EQ.1.AND.ZC.GT.0.49D0).OR.(MSTJ(41).GE.2.AND.
1499      &MIN(ZC,ZCE).GT.0.4999D0)).AND.IPSPD.EQ.0) THEN
1500         P(IEP(1),5)=PMTH(1,IR)
1501         V(IEP(1),5)=P(IEP(1),5)**2
1502         GOTO 450
1503       ENDIF
1504
1505 C...Integral of Altarelli-Parisi z kernel for QCD.
1506 C...(Includes squark and gluino; with factor N_C/C_F extra for latter).
1507       IF(MSTJ(49).EQ.0.AND.KFL(1).EQ.21) THEN
1508 Cacs+
1509 C      FBR= 6D0*LOG((1D0-ZC)/ZC)+MSTJ(45)*0.5D0
1510       FBR=dgauss1(splitg1,zc,1.d0-zc,1.d-3)
1511 Cacs-
1512 C...QUARKONIA+++
1513 C...Evolution of QQ~[3S18] state if MSTP(148)=1.
1514       ELSEIF(MSTJ(49).EQ.0.AND.MSTP(149).GE.0.AND.
1515      &       (KFL(1).EQ.9900443.OR.KFL(1).EQ.9900553)) THEN
1516         FBR=6D0*LOG((1D0-ZC)/ZC)
1517 C...QUARKONIA---
1518       ELSEIF(MSTJ(49).EQ.0) THEN
1519 Cacs+
1520 C      FBR=(8D0/3D0)*LOG((1D0-ZC)/ZC)
1521       FBR=dgauss1(splitq1,zc,1.d0-zc,1.d-3)
1522
1523 Cacs-
1524         IF(IGLUI.EQ.1.AND.IR.GE.31) FBR=FBR*(9D0/4D0)
1525
1526 C...Integral of Altarelli-Parisi z kernel for scalar gluon.
1527       ELSEIF(MSTJ(49).EQ.1.AND.KFL(1).EQ.21) THEN
1528         FBR=(PARJ(87)+MSTJ(45)*PARJ(88))*(1D0-2D0*ZC)
1529       ELSEIF(MSTJ(49).EQ.1) THEN
1530         FBR=(1D0-2D0*ZC)/3D0
1531         IF(IGM.EQ.0.AND.M3JC.GE.1) FBR=4D0*FBR
1532
1533 C...Integral of Altarelli-Parisi z kernel for Abelian vector gluon.
1534       ELSEIF(KFL(1).EQ.21) THEN
1535         FBR=6D0*MSTJ(45)*(0.5D0-ZC)
1536       ELSE
1537         FBR=2D0*LOG((1D0-ZC)/ZC)
1538       ENDIF
1539
1540 C...Reset QCD probability for colourless.
1541       IF(ISCOL(IR).EQ.0) FBR=0D0
1542
1543 C...Integral of Altarelli-Parisi kernel for photon emission.
1544       FBRE=0D0
1545       IF(MSTJ(41).GE.2.AND.ISCHG(IR).EQ.1) THEN
1546         IF(KFL(1).LE.18) THEN
1547           FBRE=(KCHG(KFL(1),1)/3D0)**2*2D0*LOG((1D0-ZCE)/ZCE)
1548         ENDIF
1549         IF(MSTJ(41).EQ.10) FBRE=PARJ(84)*FBRE
1550       ENDIF
1551
1552 C...Inner veto algorithm starts. Find maximum mass for evolution.
1553   410 PMS=V(IEP(1),5)
1554       IF(IGM.GE.0) THEN
1555         PM2=0D0
1556         DO 420 I=2,NEP
1557           PM=P(IEP(I),5)
1558           IRI=IREF(IEP(I)-NS)
1559           IF(KSH(IRI).EQ.1) PM=PMTH(2,IRI)
1560           PM2=PM2+PM
1561   420   CONTINUE
1562         PMS=MIN(PMS,(P(IM,5)-PM2)**2)
1563       ENDIF
1564
1565 C...Select mass for daughter in QCD evolution.
1566       B0=27D0/6D0
1567       DO 430 IFF=4,MSTJ(45)
1568         IF(PMS.GT.4D0*PMTH(2,IFF)**2) B0=(33D0-2D0*IFF)/6D0
1569   430 CONTINUE
1570 C...Shift m^2 for evolution in Q^2 = m^2 - m(onshell)^2.
1571       PMSC=MAX(0.5D0*PARJ(82),PMS-PMTH(1,IR)**2)
1572 C...Already predetermined choice.
1573       IF(IPSPD.NE.0) THEN
1574         PMSQCD=P(IPSPD,5)**2
1575       ELSEIF(FBR.LT.1D-3) THEN
1576         PMSQCD=0D0
1577       ELSEIF(MSTJ(44).LE.0) THEN
1578         PMSQCD=PMSC*EXP(MAX(-50D0,LOG(PYR(0))*PARU(2)/(PARU(111)*FBR)))
1579       ELSEIF(MSTJ(44).EQ.1) THEN
1580         PMSQCD=4D0*ALAMS*(0.25D0*PMSC/ALAMS)**(PYR(0)**(B0/FBR))
1581       ELSE
1582         PMSQCD=PMSC*EXP(MAX(-50D0,ALFM*B0*LOG(PYR(0))/FBR))
1583       ENDIF
1584 C...Shift back m^2 from evolution in Q^2 = m^2 - m(onshell)^2.
1585       IF(IPSPD.EQ.0) PMSQCD=PMSQCD+PMTH(1,IR)**2
1586       IF(ZC.GT.0.49D0.OR.PMSQCD.LE.PMTH(4,IR)**2) PMSQCD=PMTH(2,IR)**2
1587       V(IEP(1),5)=PMSQCD
1588       MCE=1
1589
1590 C...Select mass for daughter in QED evolution.
1591       IF(MSTJ(41).GE.2.AND.ISCHG(IR).EQ.1.AND.IPSPD.EQ.0) THEN
1592 C...Shift m^2 for evolution in Q^2 = m^2 - m(onshell)^2.
1593         PMSE=MAX(0.5D0*PARJ(83),PMS-PMTH(1,IR)**2)
1594         IF(FBRE.LT.1D-3) THEN
1595           PMSQED=0D0
1596         ELSE
1597           PMSQED=PMSE*EXP(MAX(-50D0,LOG(PYR(0))*PARU(2)/
1598      &    (PARU(101)*FBRE)))
1599         ENDIF
1600 C...Shift back m^2 from evolution in Q^2 = m^2 - m(onshell)^2.
1601         PMSQED=PMSQED+PMTH(1,IR)**2
1602         IF(ZCE.GT.0.4999D0.OR.PMSQED.LE.PMTH(5,IR)**2) PMSQED=
1603      &  PMTH(2,IR)**2
1604         IF(PMSQED.GT.PMSQCD) THEN
1605           V(IEP(1),5)=PMSQED
1606           MCE=2
1607         ENDIF
1608       ENDIF
1609
1610 C...Check whether daughter mass below cutoff.
1611       P(IEP(1),5)=SQRT(V(IEP(1),5))
1612       IF(P(IEP(1),5).LE.PMTH(3,IR)) THEN
1613         P(IEP(1),5)=PMTH(1,IR)
1614         V(IEP(1),5)=P(IEP(1),5)**2
1615         GOTO 450
1616       ENDIF
1617 Cacs+
1618        virt=V(IEP(1),5)
1619 Cacs-
1620
1621 C...Already predetermined choice of z, and flavour in g -> qqbar.
1622       IF(IPSPD.NE.0) THEN
1623         IPSGD1=K(IPSPD,4)
1624         IPSGD2=K(IPSPD,5)
1625         PMSGD1=P(IPSGD1,5)**2
1626         PMSGD2=P(IPSGD2,5)**2
1627         ALAMPS=SQRT(MAX(1D-10,(PMSQCD-PMSGD1-PMSGD2)**2-
1628      &  4D0*PMSGD1*PMSGD2))
1629         Z=0.5D0*(PMSQCD*(2D0*P(IPSGD1,4)/P(IPSPD,4)-1D0)+ALAMPS-
1630      &  PMSGD1+PMSGD2)/ALAMPS
1631         Z=MAX(0.00001D0,MIN(0.99999D0,Z))
1632         IF(KFL(1).NE.21) THEN
1633           K(IEP(1),5)=21
1634         ELSE
1635           K(IEP(1),5)=IABS(K(IPSGD1,2))
1636         ENDIF
1637
1638 C...Select z value of branching: q -> qgamma.
1639       ELSEIF(MCE.EQ.2) THEN
1640         Z=1D0-(1D0-ZCE)*(ZCE/(1D0-ZCE))**PYR(0)
1641         IF(1D0+Z**2.LT.2D0*PYR(0)) GOTO 410
1642         K(IEP(1),5)=22
1643
1644 C...QUARKONIA+++
1645 C...Select z value of branching: QQ~[3S18] -> QQ~[3S18]g.
1646       ELSEIF(MSTJ(49).EQ.0.AND.
1647      &       (KFL(1).EQ.9900443.OR.KFL(1).EQ.9900553)) THEN
1648         Z=(1D0-ZC)*(ZC/(1D0-ZC))**PYR(0)
1649 C...Select always the harder 'gluon' if the switch MSTP(149)<=0.
1650         IF(MSTP(149).LE.0.OR.PYR(0).GT.0.5D0) Z=1D0-Z
1651         IF((1D0-Z*(1D0-Z))**2.LT.PYR(0)) GOTO 410
1652         K(IEP(1),5)=21
1653 C...QUARKONIA---
1654
1655 C...Select z value of branching: q -> qg, g -> gg, g -> qqbar.
1656       ELSEIF(MSTJ(49).NE.1.AND.KFL(1).NE.21) THEN
1657 Cacs+
1658 C        Z=1D0-(1D0-ZC)*(ZC/(1D0-ZC))**PYR(0)
1659 C...Only do z weighting when no ME correction afterwards.
1660 C        IF(M3JC.EQ.0.AND.1D0+Z**2.LT.2D0*PYR(0)) GOTO 410
1661 C
1662         anfbr=dgauss1(splitq2,zc,1.d0-zc,1.d-3)
1663         z=simdis(500,zc,1,anfbr)
1664 Cacs-
1665         K(IEP(1),5)=21
1666       ELSEIF(MSTJ(49).EQ.0.AND.MSTJ(45)*0.5D0.LT.PYR(0)*FBR) THEN
1667 Cacs+
1668 c        Z=(1D0-ZC)*(ZC/(1D0-ZC))**PYR(0)
1669         anfbr=dgauss1(splitg2,zc,1.d0-zc,1.d-3)
1670
1671         z=simdis(500,zc,21,anfbr)
1672
1673         IF(PYR(0).GT.0.5D0) Z=1D0-Z
1674 c        IF((1D0-Z*(1D0-Z))**2.LT.PYR(0)) GOTO 410
1675 Cacs-
1676         K(IEP(1),5)=21
1677       ELSEIF(MSTJ(49).NE.1) THEN
1678 Cacs+
1679 c        Z=PYR(0)
1680 c        IF(Z**2+(1D0-Z)**2.LT.PYR(0)) GOTO 410
1681         anfbr=dgauss1(splitqqbar,zc,1.d0-zc,1.d-3)
1682         z=simdis(500,zc,3,anfbr)
1683
1684 Cacs-
1685         KFLB=1+INT(MSTJ(45)*PYR(0))
1686         PMQ=4D0*PMTH(2,KFLB)**2/V(IEP(1),5)
1687         IF(PMQ.GE.1D0) GOTO 410
1688         IF(MSTJ(44).LE.2.OR.MSTJ(44).EQ.4) THEN
1689           IF(Z.LT.ZC.OR.Z.GT.1D0-ZC) GOTO 410
1690           PMQ0=4D0*PMTH(2,21)**2/V(IEP(1),5)
1691           IF(MOD(MSTJ(43),2).EQ.0.AND.(1D0+0.5D0*PMQ)*SQRT(1D0-PMQ)
1692      &    .LT.PYR(0)*(1D0+0.5D0*PMQ0)*SQRT(1D0-PMQ0)) GOTO 410
1693         ELSE
1694           IF((1D0+0.5D0*PMQ)*SQRT(1D0-PMQ).LT.PYR(0)) GOTO 410
1695         ENDIF
1696         K(IEP(1),5)=KFLB
1697
1698 C...Ditto for scalar gluon model.
1699       ELSEIF(KFL(1).NE.21) THEN
1700         Z=1D0-SQRT(ZC**2+PYR(0)*(1D0-2D0*ZC))
1701         K(IEP(1),5)=21
1702       ELSEIF(PYR(0)*(PARJ(87)+MSTJ(45)*PARJ(88)).LE.PARJ(87)) THEN
1703         Z=ZC+(1D0-2D0*ZC)*PYR(0)
1704         K(IEP(1),5)=21
1705       ELSE
1706         Z=ZC+(1D0-2D0*ZC)*PYR(0)
1707         KFLB=1+INT(MSTJ(45)*PYR(0))
1708         PMQ=4D0*PMTH(2,KFLB)**2/V(IEP(1),5)
1709         IF(PMQ.GE.1D0) GOTO 410
1710         K(IEP(1),5)=KFLB
1711       ENDIF
1712
1713 C...Correct to alpha_s(pT^2) (optionally m^2/4 for g -> q qbar).
1714       IF(MCE.EQ.1.AND.MSTJ(44).GE.2.AND.IPSPD.EQ.0) THEN
1715         IF(KFL(1).EQ.21.AND.K(IEP(1),5).LT.10.AND.
1716      &  (MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
1717           IF(ALFM/LOG(V(IEP(1),5)*0.25D0/ALAMS).LT.PYR(0)) GOTO 410
1718         ELSE
1719           PT2APP=Z*(1D0-Z)*V(IEP(1),5)
1720           IF(MSTJ(44).GE.4) PT2APP=PT2APP*
1721      &    (1D0-PMTH(1,IR)**2/V(IEP(1),5))**2
1722           IF(PT2APP.LT.PT2MIN) GOTO 410
1723           IF(ALFM/LOG(PT2APP/ALAMS).LT.PYR(0)) GOTO 410
1724         ENDIF
1725       ENDIF
1726
1727 C...Check if z consistent with chosen m.
1728       IF(KFL(1).EQ.21) THEN
1729         IRGD1=IABS(K(IEP(1),5))
1730         IRGD2=IRGD1
1731       ELSE
1732         IRGD1=IR
1733         IRGD2=IABS(K(IEP(1),5))
1734       ENDIF
1735       IF(NEP.EQ.1) THEN
1736         PED=PS(4)
1737       ELSEIF(NEP.GE.3) THEN
1738         PED=P(IEP(1),4)
1739       ELSEIF(IGM.EQ.0.OR.MSTJ(43).LE.2) THEN
1740         PED=0.5D0*(V(IM,5)+V(IEP(1),5)-PM2**2)/P(IM,5)
1741       ELSE
1742         IF(IEP(1).EQ.N+1) PED=V(IM,1)*PEM
1743         IF(IEP(1).EQ.N+2) PED=(1D0-V(IM,1))*PEM
1744       ENDIF
1745       IF(MOD(MSTJ(43),2).EQ.1) THEN
1746         PMQTH3=0.5D0*PARJ(82)
1747         IF(IRGD2.EQ.22) PMQTH3=0.5D0*PARJ(83)
1748         IF(IRGD2.EQ.22.AND.ISCOL(IR).EQ.0) PMQTH3=0.5D0*PARJ(90)
1749         PMQ1=(PMTH(1,IRGD1)**2+PMQTH3**2)/V(IEP(1),5)
1750         PMQ2=(PMTH(1,IRGD2)**2+PMQTH3**2)/V(IEP(1),5)
1751         ZD=SQRT(MAX(0D0,(1D0-V(IEP(1),5)/PED**2)*((1D0-PMQ1-PMQ2)**2-
1752      &  4D0*PMQ1*PMQ2)))
1753         ZH=1D0+PMQ1-PMQ2
1754       ELSE
1755         ZD=SQRT(MAX(0D0,1D0-V(IEP(1),5)/PED**2))
1756         ZH=1D0
1757       ENDIF
1758       IF(KFL(1).EQ.21.AND.K(IEP(1),5).LT.10.AND.
1759      &(MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
1760       ELSEIF(IPSPD.NE.0) THEN
1761       ELSE
1762         ZL=0.5D0*(ZH-ZD)
1763         ZU=0.5D0*(ZH+ZD)
1764         IF(Z.LT.ZL.OR.Z.GT.ZU) GOTO 410
1765       ENDIF
1766       IF(KFL(1).EQ.21) V(IEP(1),3)=LOG(ZU*(1D0-ZL)/MAX(1D-20,ZL*
1767      &(1D0-ZU)))
1768       IF(KFL(1).NE.21) V(IEP(1),3)=LOG((1D0-ZL)/MAX(1D-10,1D0-ZU))
1769
1770 C...Width suppression for q -> q + g.
1771       IF(MSTJ(40).NE.0.AND.KFL(1).NE.21.AND.IPSPD.EQ.0) THEN
1772         IF(IGM.EQ.0) THEN
1773           EGLU=0.5D0*PS(5)*(1D0-Z)*(1D0+V(IEP(1),5)/V(NS+1,5))
1774         ELSE
1775           EGLU=PMED*(1D0-Z)
1776         ENDIF
1777         CHI=PARJ(89)**2/(PARJ(89)**2+EGLU**2)
1778         IF(MSTJ(40).EQ.1) THEN
1779           IF(CHI.LT.PYR(0)) GOTO 410
1780         ELSEIF(MSTJ(40).EQ.2) THEN
1781           IF(1D0-CHI.LT.PYR(0)) GOTO 410
1782         ENDIF
1783       ENDIF
1784
1785 C...Three-jet matrix element correction.
1786       IF(M3JC.GE.1) THEN
1787         WME=1D0
1788         WSHOW=1D0
1789
1790 C...QED matrix elements: only for massless case so far.
1791         IF(MCE.EQ.2.AND.IGM.EQ.0) THEN
1792           X1=Z*(1D0+V(IEP(1),5)/V(NS+1,5))
1793           X2=1D0-V(IEP(1),5)/V(NS+1,5)
1794           X3=(1D0-X1)+(1D0-X2)
1795           KI1=K(IPA(INUM),2)
1796           KI2=K(IPA(3-INUM),2)
1797           QF1=KCHG(PYCOMP(KI1),1)*ISIGN(1,KI1)/3D0
1798           QF2=KCHG(PYCOMP(KI2),1)*ISIGN(1,KI2)/3D0
1799           WSHOW=QF1**2*(1D0-X1)/X3*(1D0+(X1/(2D0-X2))**2)+
1800      &    QF2**2*(1D0-X2)/X3*(1D0+(X2/(2D0-X1))**2)
1801           WME=(QF1*(1D0-X1)/X3-QF2*(1D0-X2)/X3)**2*(X1**2+X2**2)
1802         ELSEIF(MCE.EQ.2) THEN
1803
1804 C...QCD matrix elements, including mass effects.
1805         ELSEIF(MSTJ(49).NE.1.AND.K(IEP(1),2).NE.21) THEN
1806           PS1ME=V(IEP(1),5)
1807           PM1ME=PMTH(1,IR)
1808           M3JCC=M3JC
1809           IF(IR.GE.31.AND.IGM.EQ.0) THEN
1810 C...QCD ME: original parton, first branching.
1811             PM2ME=PMTH(1,63-IR)
1812             ECMME=PS(5)
1813           ELSEIF(IR.GE.31) THEN
1814 C...QCD ME: original parton, subsequent branchings.
1815             PM2ME=PMTH(1,63-IR)
1816             PEDME=PEM*(V(IM,1)+(1D0-V(IM,1))*PS1ME/V(IM,5))
1817             ECMME=PEDME+SQRT(MAX(0D0,PEDME**2-PS1ME+PM2ME**2))
1818           ELSEIF(K(IM,2).EQ.21) THEN
1819 C...QCD ME: secondary partons, first branching.
1820             PM2ME=PM1ME
1821             ZMME=V(IM,1)
1822             IF(IEP(1).GT.IEP(2)) ZMME=1D0-ZMME
1823             PMLME=SQRT(MAX(0D0,(V(IM,5)-PS1ME-PM2ME**2)**2-
1824      &      4D0*PS1ME*PM2ME**2))
1825             PEDME=PEM*(0.5D0*(V(IM,5)-PMLME+PS1ME-PM2ME**2)+PMLME*ZMME)/
1826      &      V(IM,5)
1827             ECMME=PEDME+SQRT(MAX(0D0,PEDME**2-PS1ME+PM2ME**2))
1828             M3JCC=66
1829           ELSE
1830 C...QCD ME: secondary partons, subsequent branchings.
1831             PM2ME=PM1ME
1832             PEDME=PEM*(V(IM,1)+(1D0-V(IM,1))*PS1ME/V(IM,5))
1833             ECMME=PEDME+SQRT(MAX(0D0,PEDME**2-PS1ME+PM2ME**2))
1834             M3JCC=66
1835           ENDIF
1836 C...Construct ME variables.
1837           R1ME=PM1ME/ECMME
1838           R2ME=PM2ME/ECMME
1839           X1=(1D0+PS1ME/ECMME**2-R2ME**2)*(Z+(1D0-Z)*PM1ME**2/PS1ME)
1840           X2=1D0+R2ME**2-PS1ME/ECMME**2
1841 C...Call ME, with right order important for two inequivalent showerers.
1842           IF(IR.EQ.IORD+30) THEN
1843             WME=PYMAEL(M3JCC,X1,X2,R1ME,R2ME,ALPHA)
1844           ELSE
1845             WME=PYMAEL(M3JCC,X2,X1,R2ME,R1ME,ALPHA)
1846           ENDIF
1847 C...Split up total ME when two radiating partons.
1848           ISPRAD=1
1849           IF((M3JCC.GE.16.AND.M3JCC.LE.19).OR.
1850      &    (M3JCC.GE.26.AND.M3JCC.LE.29).OR.
1851      &    (M3JCC.GE.36.AND.M3JCC.LE.39).OR.
1852      &    (M3JCC.GE.46.AND.M3JCC.LE.49).OR.
1853      &    (M3JCC.GE.56.AND.M3JCC.LE.64)) ISPRAD=0
1854           IF(ISPRAD.EQ.1) WME=WME*MAX(1D-10,1D0+R1ME**2-R2ME**2-X1)/
1855      &    MAX(1D-10,2D0-X1-X2)
1856 C...Evaluate shower rate to be compared with.
1857           WSHOW=2D0/(MAX(1D-10,2D0-X1-X2)*
1858      &    MAX(1D-10,1D0+R2ME**2-R1ME**2-X2))
1859           IF(IGLUI.EQ.1.AND.IR.GE.31) WSHOW=(9D0/4D0)*WSHOW
1860         ELSEIF(MSTJ(49).NE.1) THEN
1861
1862 C...Toy model scalar theory matrix elements; no mass effects.
1863         ELSE
1864           X1=Z*(1D0+V(IEP(1),5)/V(NS+1,5))
1865           X2=1D0-V(IEP(1),5)/V(NS+1,5)
1866           X3=(1D0-X1)+(1D0-X2)
1867           WSHOW=4D0*X3*((1D0-X1)/(2D0-X2)**2+(1D0-X2)/(2D0-X1)**2)
1868           WME=X3**2
1869           IF(MSTJ(102).GE.2) WME=X3**2-2D0*(1D0+X3)*(1D0-X1)*(1D0-X2)*
1870      &    PARJ(171)
1871         ENDIF
1872
1873         IF(WME.LT.PYR(0)*WSHOW) GOTO 410
1874       ENDIF
1875
1876 C...Impose angular ordering by rejection of nonordered emission.
1877       IF(MCE.EQ.1.AND.IGM.GT.0.AND.MSTJ(42).GE.2.AND.IPSPD.EQ.0) THEN
1878         PEMAO=V(IM,1)*P(IM,4)
1879         IF(IEP(1).EQ.N+2) PEMAO=(1D0-V(IM,1))*P(IM,4)
1880         IF(IR.GE.31.AND.MSTJ(42).GE.5) THEN
1881           MAOD=0
1882         ELSEIF(KFL(1).EQ.21.AND.K(IEP(1),5).LE.10.AND.(MSTJ(42).EQ.4
1883      &  .OR.MSTJ(42).EQ.7)) THEN
1884           MAOD=0
1885         ELSEIF(KFL(1).EQ.21.AND.K(IEP(1),5).LE.10.AND.(MSTJ(42).EQ.3
1886      &  .OR.MSTJ(42).EQ.6)) THEN
1887           MAOD=1
1888           PMDAO=PMTH(2,K(IEP(1),5))
1889           THE2ID=Z*(1D0-Z)*PEMAO**2/(V(IEP(1),5)-4D0*PMDAO**2)
1890         ELSE
1891           MAOD=1
1892           THE2ID=Z*(1D0-Z)*PEMAO**2/V(IEP(1),5)
1893           IF(MSTJ(42).GE.3.AND.MSTJ(42).NE.5) THE2ID=THE2ID*
1894      &    (1D0+PMTH(1,IR)**2*(1D0-Z)/(V(IEP(1),5)*Z))**2
1895         ENDIF
1896         MAOM=1
1897         IAOM=IM
1898   440   IF(K(IAOM,5).EQ.22) THEN
1899           IAOM=K(IAOM,3)
1900           IF(K(IAOM,3).LE.NS) MAOM=0
1901           IF(MAOM.EQ.1) GOTO 440
1902         ENDIF
1903         IF(MAOM.EQ.1.AND.MAOD.EQ.1) THEN
1904           THE2IM=V(IAOM,1)*(1D0-V(IAOM,1))*P(IAOM,4)**2/V(IAOM,5)
1905           IF(THE2ID.LT.THE2IM) GOTO 410
1906         ENDIF
1907       ENDIF
1908
1909 C...Impose user-defined maximum angle at first branching.
1910       IF(MSTJ(48).EQ.1.AND.IPSPD.EQ.0) THEN
1911         IF(NEP.EQ.1.AND.IM.EQ.NS) THEN
1912           THE2ID=Z*(1D0-Z)*PS(4)**2/V(IEP(1),5)
1913           IF(PARJ(85)**2*THE2ID.LT.1D0) GOTO 410
1914         ELSEIF(NEP.EQ.2.AND.IEP(1).EQ.NS+2) THEN
1915           THE2ID=Z*(1D0-Z)*(0.5D0*P(IM,4))**2/V(IEP(1),5)
1916           IF(PARJ(85)**2*THE2ID.LT.1D0) GOTO 410
1917         ELSEIF(NEP.EQ.2.AND.IEP(1).EQ.NS+3) THEN
1918           THE2ID=Z*(1D0-Z)*(0.5D0*P(IM,4))**2/V(IEP(1),5)
1919           IF(PARJ(86)**2*THE2ID.LT.1D0) GOTO 410
1920         ENDIF
1921       ENDIF
1922
1923 C...Impose angular constraint in first branching from interference
1924 C...with initial state partons.
1925       IF(MIIS.GE.2.AND.IEP(1).LE.NS+3) THEN
1926         THE2D=MAX((1D0-Z)/Z,Z/(1D0-Z))*V(IEP(1),5)/(0.5D0*P(IM,4))**2
1927         IF(IEP(1).EQ.NS+2.AND.ISII(1).GE.1) THEN
1928           IF(THE2D.GT.THEIIS(1,ISII(1))**2) GOTO 410
1929         ELSEIF(IEP(1).EQ.NS+3.AND.ISII(2).GE.1) THEN
1930           IF(THE2D.GT.THEIIS(2,ISII(2))**2) GOTO 410
1931         ENDIF
1932       ENDIF
1933
1934 C...End of inner veto algorithm. Check if only one leg evolved so far.
1935   450 V(IEP(1),1)=Z
1936       ISL(1)=0
1937       ISL(2)=0
1938       IF(NEP.EQ.1) GOTO 490
1939       IF(NEP.EQ.2.AND.P(IEP(1),5)+P(IEP(2),5).GE.P(IM,5)) GOTO 350
1940       DO 460 I=1,NEP
1941         IR=IREF(N+I-NS)
1942         IF(ITRY(I).EQ.0.AND.KSH(IR).EQ.1) THEN
1943           IF(P(N+I,5).GE.PMTH(2,IR)) GOTO 350
1944         ENDIF
1945   460 CONTINUE
1946
1947 C...Check if chosen multiplet m1,m2,z1,z2 is physical.
1948       IF(NEP.GE.3) THEN
1949         PMSUM=0D0
1950         DO 470 I=1,NEP
1951           PMSUM=PMSUM+P(N+I,5)
1952   470   CONTINUE
1953         IF(PMSUM.GE.PS(5)) GOTO 350
1954       ELSEIF(IGM.EQ.0.OR.MSTJ(43).LE.2.OR.MOD(MSTJ(43),2).EQ.0) THEN
1955         DO 480 I1=N+1,N+2
1956           IRDA=IREF(I1-NS)
1957           IF(KSH(IRDA).EQ.0) GOTO 480
1958           IF(P(I1,5).LT.PMTH(2,IRDA)) GOTO 480
1959           IF(IRDA.EQ.21) THEN
1960             IRGD1=IABS(K(I1,5))
1961             IRGD2=IRGD1
1962           ELSE
1963             IRGD1=IRDA
1964             IRGD2=IABS(K(I1,5))
1965           ENDIF
1966           I2=2*N+3-I1
1967           IF(IGM.EQ.0.OR.MSTJ(43).LE.2) THEN
1968             PED=0.5D0*(V(IM,5)+V(I1,5)-V(I2,5))/P(IM,5)
1969           ELSE
1970             IF(I1.EQ.N+1) ZM=V(IM,1)
1971             IF(I1.EQ.N+2) ZM=1D0-V(IM,1)
1972             PML=SQRT((V(IM,5)-V(N+1,5)-V(N+2,5))**2-
1973      &      4D0*V(N+1,5)*V(N+2,5))
1974             PED=PEM*(0.5D0*(V(IM,5)-PML+V(I1,5)-V(I2,5))+PML*ZM)/
1975      &      V(IM,5)
1976           ENDIF
1977           IF(MOD(MSTJ(43),2).EQ.1) THEN
1978             PMQTH3=0.5D0*PARJ(82)
1979             IF(IRGD2.EQ.22) PMQTH3=0.5D0*PARJ(83)
1980             IF(IRGD2.EQ.22.AND.ISCOL(IRDA).EQ.0) PMQTH3=0.5D0*PARJ(90)
1981             PMQ1=(PMTH(1,IRGD1)**2+PMQTH3**2)/V(I1,5)
1982             PMQ2=(PMTH(1,IRGD2)**2+PMQTH3**2)/V(I1,5)
1983             ZD=SQRT(MAX(0D0,(1D0-V(I1,5)/PED**2)*((1D0-PMQ1-PMQ2)**2-
1984      &      4D0*PMQ1*PMQ2)))
1985             ZH=1D0+PMQ1-PMQ2
1986           ELSE
1987             ZD=SQRT(MAX(0D0,1D0-V(I1,5)/PED**2))
1988             ZH=1D0
1989           ENDIF
1990           IF(IRDA.EQ.21.AND.IRGD1.LT.10.AND.
1991      &    (MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
1992           ELSE
1993             ZL=0.5D0*(ZH-ZD)
1994             ZU=0.5D0*(ZH+ZD)
1995             IF(I1.EQ.N+1.AND.(V(I1,1).LT.ZL.OR.V(I1,1).GT.ZU).AND.
1996      &      ISSET(1).EQ.0) THEN
1997               ISL(1)=1
1998             ELSEIF(I1.EQ.N+2.AND.(V(I1,1).LT.ZL.OR.V(I1,1).GT.ZU).AND.
1999      &      ISSET(2).EQ.0) THEN
2000               ISL(2)=1
2001             ENDIF
2002           ENDIF
2003           IF(IRDA.EQ.21) V(I1,4)=LOG(ZU*(1D0-ZL)/MAX(1D-20,
2004      &    ZL*(1D0-ZU)))
2005           IF(IRDA.NE.21) V(I1,4)=LOG((1D0-ZL)/MAX(1D-10,1D0-ZU))
2006   480   CONTINUE
2007         IF(ISL(1).EQ.1.AND.ISL(2).EQ.1.AND.ISLM.NE.0) THEN
2008           ISL(3-ISLM)=0
2009           ISLM=3-ISLM
2010         ELSEIF(ISL(1).EQ.1.AND.ISL(2).EQ.1) THEN
2011           ZDR1=MAX(0D0,V(N+1,3)/MAX(1D-6,V(N+1,4))-1D0)
2012           ZDR2=MAX(0D0,V(N+2,3)/MAX(1D-6,V(N+2,4))-1D0)
2013           IF(ZDR2.GT.PYR(0)*(ZDR1+ZDR2)) ISL(1)=0
2014           IF(ISL(1).EQ.1) ISL(2)=0
2015           IF(ISL(1).EQ.0) ISLM=1
2016           IF(ISL(2).EQ.0) ISLM=2
2017         ENDIF
2018         IF(ISL(1).EQ.1.OR.ISL(2).EQ.1) GOTO 350
2019       ENDIF
2020       IRD1=IREF(N+1-NS)
2021       IRD2=IREF(N+2-NS)
2022       IF(IGM.GT.0) THEN
2023         IF(MOD(MSTJ(43),2).EQ.1.AND.(P(N+1,5).GE.
2024      &  PMTH(2,IRD1).OR.P(N+2,5).GE.PMTH(2,IRD2))) THEN
2025           PMQ1=V(N+1,5)/V(IM,5)
2026           PMQ2=V(N+2,5)/V(IM,5)
2027           ZD=SQRT(MAX(0D0,(1D0-V(IM,5)/PEM**2)*((1D0-PMQ1-PMQ2)**2-
2028      &    4D0*PMQ1*PMQ2)))
2029           ZH=1D0+PMQ1-PMQ2
2030           ZL=0.5D0*(ZH-ZD)
2031           ZU=0.5D0*(ZH+ZD)
2032           IF(V(IM,1).LT.ZL.OR.V(IM,1).GT.ZU) GOTO 350
2033         ENDIF
2034       ENDIF
2035
2036 C...Accepted branch. Construct four-momentum for initial partons.
2037   490 MAZIP=0
2038       MAZIC=0
2039       IF(NEP.EQ.1) THEN
2040         P(N+1,1)=0D0
2041         P(N+1,2)=0D0
2042         P(N+1,3)=SQRT(MAX(0D0,(P(IPA(1),4)+P(N+1,5))*(P(IPA(1),4)-
2043      &  P(N+1,5))))
2044         P(N+1,4)=P(IPA(1),4)
2045         V(N+1,2)=P(N+1,4)
2046       ELSEIF(IGM.EQ.0.AND.NEP.EQ.2) THEN
2047         PED1=0.5D0*(V(IM,5)+V(N+1,5)-V(N+2,5))/P(IM,5)
2048         P(N+1,1)=0D0
2049         P(N+1,2)=0D0
2050         P(N+1,3)=SQRT(MAX(0D0,(PED1+P(N+1,5))*(PED1-P(N+1,5))))
2051         P(N+1,4)=PED1
2052         P(N+2,1)=0D0
2053         P(N+2,2)=0D0
2054         P(N+2,3)=-P(N+1,3)
2055         P(N+2,4)=P(IM,5)-PED1
2056         V(N+1,2)=P(N+1,4)
2057         V(N+2,2)=P(N+2,4)
2058       ELSEIF(NEP.GE.3) THEN
2059 C...Rescale all momenta for energy conservation.
2060         LOOP=0
2061         PES=0D0
2062         PQS=0D0
2063         DO 510 I=1,NEP
2064           DO 500 J=1,4
2065             P(N+I,J)=P(IPA(I),J)
2066   500     CONTINUE
2067           PES=PES+P(N+I,4)
2068           PQS=PQS+P(N+I,5)**2/P(N+I,4)
2069   510   CONTINUE
2070   520   LOOP=LOOP+1
2071         FAC=(PS(5)-PQS)/(PES-PQS)
2072         PES=0D0
2073         PQS=0D0
2074         DO 540 I=1,NEP
2075           DO 530 J=1,3
2076             P(N+I,J)=FAC*P(N+I,J)
2077   530     CONTINUE
2078           P(N+I,4)=SQRT(P(N+I,5)**2+P(N+I,1)**2+P(N+I,2)**2+P(N+I,3)**2)
2079           V(N+I,2)=P(N+I,4)
2080           PES=PES+P(N+I,4)
2081           PQS=PQS+P(N+I,5)**2/P(N+I,4)
2082   540   CONTINUE
2083         IF(LOOP.LT.10.AND.ABS(PES-PS(5)).GT.1D-12*PS(5)) GOTO 520
2084
2085 C...Construct transverse momentum for ordinary branching in shower.
2086       ELSE
2087         ZM=V(IM,1)
2088         LOOPPT=0
2089   550   LOOPPT=LOOPPT+1
2090         PZM=SQRT(MAX(0D0,(PEM+P(IM,5))*(PEM-P(IM,5))))
2091         PMLS=(V(IM,5)-V(N+1,5)-V(N+2,5))**2-4D0*V(N+1,5)*V(N+2,5)
2092         IF(PZM.LE.0D0) THEN
2093           PTS=0D0
2094         ELSEIF(K(IM,2).EQ.21.AND.IABS(K(N+1,2)).LE.10.AND.
2095      &  (MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
2096           PTS=PMLS*ZM*(1D0-ZM)/V(IM,5)
2097         ELSEIF(MOD(MSTJ(43),2).EQ.1) THEN
2098           PTS=(PEM**2*(ZM*(1D0-ZM)*V(IM,5)-(1D0-ZM)*V(N+1,5)-
2099      &    ZM*V(N+2,5))-0.25D0*PMLS)/PZM**2
2100         ELSE
2101           PTS=PMLS*(ZM*(1D0-ZM)*PEM**2/V(IM,5)-0.25D0)/PZM**2
2102         ENDIF
2103         IF(PTS.LT.0D0.AND.LOOPPT.LT.10) THEN
2104           ZM=0.05D0+0.9D0*ZM
2105           GOTO 550
2106         ELSEIF(PTS.LT.0D0) THEN
2107           GOTO 280
2108         ENDIF
2109         PT=SQRT(MAX(0D0,PTS))
2110
2111 C...Global statistics.
2112         MINT(353)=MINT(353)+1
2113         VINT(353)=VINT(353)+PT
2114         IF (MINT(353).EQ.1) VINT(358)=PT
2115
2116 C...Find coefficient of azimuthal asymmetry due to gluon polarization.
2117         HAZIP=0D0
2118         IF(MSTJ(49).NE.1.AND.MOD(MSTJ(46),2).EQ.1.AND.K(IM,2).EQ.21
2119      &  .AND.IAU.NE.0) THEN
2120           IF(K(IGM,3).NE.0) MAZIP=1
2121           ZAU=V(IGM,1)
2122           IF(IAU.EQ.IM+1) ZAU=1D0-V(IGM,1)
2123           IF(MAZIP.EQ.0) ZAU=0D0
2124           IF(K(IGM,2).NE.21) THEN
2125             HAZIP=2D0*ZAU/(1D0+ZAU**2)
2126           ELSE
2127             HAZIP=(ZAU/(1D0-ZAU*(1D0-ZAU)))**2
2128           ENDIF
2129           IF(K(N+1,2).NE.21) THEN
2130             HAZIP=HAZIP*(-2D0*ZM*(1D0-ZM))/(1D0-2D0*ZM*(1D0-ZM))
2131           ELSE
2132             HAZIP=HAZIP*(ZM*(1D0-ZM)/(1D0-ZM*(1D0-ZM)))**2
2133           ENDIF
2134         ENDIF
2135
2136 C...Find coefficient of azimuthal asymmetry due to soft gluon
2137 C...interference.
2138         HAZIC=0D0
2139         IF(MSTJ(49).NE.2.AND.MSTJ(46).GE.2.AND.(K(N+1,2).EQ.21.OR.
2140      &  K(N+2,2).EQ.21).AND.IAU.NE.0) THEN
2141           IF(K(IGM,3).NE.0) MAZIC=N+1
2142           IF(K(IGM,3).NE.0.AND.K(N+1,2).NE.21) MAZIC=N+2
2143           IF(K(IGM,3).NE.0.AND.K(N+1,2).EQ.21.AND.K(N+2,2).EQ.21.AND.
2144      &    ZM.GT.0.5D0) MAZIC=N+2
2145           IF(K(IAU,2).EQ.22) MAZIC=0
2146           ZS=ZM
2147           IF(MAZIC.EQ.N+2) ZS=1D0-ZM
2148           ZGM=V(IGM,1)
2149           IF(IAU.EQ.IM-1) ZGM=1D0-V(IGM,1)
2150           IF(MAZIC.EQ.0) ZGM=1D0
2151           IF(MAZIC.NE.0) HAZIC=(P(IM,5)/P(IGM,5))*
2152      &    SQRT((1D0-ZS)*(1D0-ZGM)/(ZS*ZGM))
2153           HAZIC=MIN(0.95D0,HAZIC)
2154         ENDIF
2155       ENDIF
2156
2157 C...Construct energies for ordinary branching in shower.
2158   560 IF(NEP.EQ.2.AND.IGM.GT.0) THEN
2159         IF(K(IM,2).EQ.21.AND.IABS(K(N+1,2)).LE.10.AND.
2160      &  (MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
2161           P(N+1,4)=0.5D0*(PEM*(V(IM,5)+V(N+1,5)-V(N+2,5))+
2162      &    PZM*SQRT(MAX(0D0,PMLS))*(2D0*ZM-1D0))/V(IM,5)
2163         ELSEIF(MOD(MSTJ(43),2).EQ.1) THEN
2164           P(N+1,4)=PEM*V(IM,1)
2165         ELSE
2166           P(N+1,4)=PEM*(0.5D0*(V(IM,5)-SQRT(PMLS)+V(N+1,5)-V(N+2,5))+
2167      &    SQRT(PMLS)*ZM)/V(IM,5)
2168         ENDIF
2169
2170 C...Already predetermined choice of phi angle or not
2171
2172         PHI=PARU(2)*PYR(0)
2173         IF(MPSPD.EQ.1.AND.IGM.EQ.NS+1) THEN
2174           IPSPD=IP1+IM-NS-2
2175           IF(K(IPSPD,4).GT.0) THEN
2176             IPSGD1=K(IPSPD,4)
2177             IF(IM.EQ.NS+2) THEN
2178               PHI=PYANGL(P(IPSGD1,1),P(IPSGD1,2))
2179             ELSE
2180               PHI=PYANGL(-P(IPSGD1,1),P(IPSGD1,2))
2181             ENDIF
2182           ENDIF
2183         ELSEIF(MPSPD.EQ.1.AND.IGM.EQ.NS+2) THEN
2184           IPSPD=IP1+IM-NS-2
2185           IF(K(IPSPD,4).GT.0) THEN
2186             IPSGD1=K(IPSPD,4)
2187             PHIPSM=PYANGL(P(IPSPD,1),P(IPSPD,2))
2188             THEPSM=PYANGL(P(IPSPD,3),SQRT(P(IPSPD,1)**2+P(IPSPD,2)**2))
2189             CALL PYROBO(IPSGD1,IPSGD1,0D0,-PHIPSM,0D0,0D0,0D0)
2190             CALL PYROBO(IPSGD1,IPSGD1,-THEPSM,0D0,0D0,0D0,0D0)
2191             PHI=PYANGL(P(IPSGD1,1),P(IPSGD1,2))
2192             CALL PYROBO(IPSGD1,IPSGD1,THEPSM,PHIPSM,0D0,0D0,0D0)
2193           ENDIF
2194         ENDIF
2195
2196 C...Construct momenta for ordinary branching in shower.
2197         P(N+1,1)=PT*COS(PHI)
2198         P(N+1,2)=PT*SIN(PHI)
2199         IF(K(IM,2).EQ.21.AND.IABS(K(N+1,2)).LE.10.AND.
2200      &  (MSTJ(44).EQ.3.OR.MSTJ(44).EQ.5)) THEN
2201           P(N+1,3)=0.5D0*(PZM*(V(IM,5)+V(N+1,5)-V(N+2,5))+
2202      &    PEM*SQRT(MAX(0D0,PMLS))*(2D0*ZM-1D0))/V(IM,5)
2203         ELSEIF(PZM.GT.0D0) THEN
2204           P(N+1,3)=0.5D0*(V(N+2,5)-V(N+1,5)-V(IM,5)+
2205      &    2D0*PEM*P(N+1,4))/PZM
2206         ELSE
2207           P(N+1,3)=0D0
2208         ENDIF
2209         P(N+2,1)=-P(N+1,1)
2210         P(N+2,2)=-P(N+1,2)
2211         P(N+2,3)=PZM-P(N+1,3)
2212         P(N+2,4)=PEM-P(N+1,4)
2213         IF(MSTJ(43).LE.2) THEN
2214           V(N+1,2)=(PEM*P(N+1,4)-PZM*P(N+1,3))/P(IM,5)
2215           V(N+2,2)=(PEM*P(N+2,4)-PZM*P(N+2,3))/P(IM,5)
2216         ENDIF
2217       ENDIF
2218
2219 C...Rotate and boost daughters.
2220       IF(IGM.GT.0) THEN
2221         IF(MSTJ(43).LE.2) THEN
2222           BEX=P(IGM,1)/P(IGM,4)
2223           BEY=P(IGM,2)/P(IGM,4)
2224           BEZ=P(IGM,3)/P(IGM,4)
2225           GA=P(IGM,4)/P(IGM,5)
2226           GABEP=GA*(GA*(BEX*P(IM,1)+BEY*P(IM,2)+BEZ*P(IM,3))/(1D0+GA)-
2227      &    P(IM,4))
2228         ELSE
2229           BEX=0D0
2230           BEY=0D0
2231           BEZ=0D0
2232           GA=1D0
2233           GABEP=0D0
2234         ENDIF
2235         PTIMB=SQRT((P(IM,1)+GABEP*BEX)**2+(P(IM,2)+GABEP*BEY)**2)
2236         THE=PYANGL(P(IM,3)+GABEP*BEZ,PTIMB)
2237         IF(PTIMB.GT.1D-4) THEN
2238           PHI=PYANGL(P(IM,1)+GABEP*BEX,P(IM,2)+GABEP*BEY)
2239         ELSE
2240           PHI=0D0
2241         ENDIF
2242         DO 570 I=N+1,N+2
2243           DP(1)=COS(THE)*COS(PHI)*P(I,1)-SIN(PHI)*P(I,2)+
2244      &    SIN(THE)*COS(PHI)*P(I,3)
2245           DP(2)=COS(THE)*SIN(PHI)*P(I,1)+COS(PHI)*P(I,2)+
2246      &    SIN(THE)*SIN(PHI)*P(I,3)
2247           DP(3)=-SIN(THE)*P(I,1)+COS(THE)*P(I,3)
2248           DP(4)=P(I,4)
2249           DBP=BEX*DP(1)+BEY*DP(2)+BEZ*DP(3)
2250           DGABP=GA*(GA*DBP/(1D0+GA)+DP(4))
2251           P(I,1)=DP(1)+DGABP*BEX
2252           P(I,2)=DP(2)+DGABP*BEY
2253           P(I,3)=DP(3)+DGABP*BEZ
2254           P(I,4)=GA*(DP(4)+DBP)
2255   570   CONTINUE
2256       ENDIF
2257
2258 C...Weight with azimuthal distribution, if required.
2259       IF(MAZIP.NE.0.OR.MAZIC.NE.0) THEN
2260         DO 580 J=1,3
2261           DPT(1,J)=P(IM,J)
2262           DPT(2,J)=P(IAU,J)
2263           DPT(3,J)=P(N+1,J)
2264   580   CONTINUE
2265         DPMA=DPT(1,1)*DPT(2,1)+DPT(1,2)*DPT(2,2)+DPT(1,3)*DPT(2,3)
2266         DPMD=DPT(1,1)*DPT(3,1)+DPT(1,2)*DPT(3,2)+DPT(1,3)*DPT(3,3)
2267         DPMM=DPT(1,1)**2+DPT(1,2)**2+DPT(1,3)**2
2268         DO 590 J=1,3
2269           DPT(4,J)=DPT(2,J)-DPMA*DPT(1,J)/MAX(1D-10,DPMM)
2270           DPT(5,J)=DPT(3,J)-DPMD*DPT(1,J)/MAX(1D-10,DPMM)
2271   590   CONTINUE
2272         DPT(4,4)=SQRT(DPT(4,1)**2+DPT(4,2)**2+DPT(4,3)**2)
2273         DPT(5,4)=SQRT(DPT(5,1)**2+DPT(5,2)**2+DPT(5,3)**2)
2274         IF(MIN(DPT(4,4),DPT(5,4)).GT.0.1D0*PARJ(82)) THEN
2275           CAD=(DPT(4,1)*DPT(5,1)+DPT(4,2)*DPT(5,2)+
2276      &    DPT(4,3)*DPT(5,3))/(DPT(4,4)*DPT(5,4))
2277           IF(MAZIP.NE.0) THEN
2278             IF(1D0+HAZIP*(2D0*CAD**2-1D0).LT.PYR(0)*(1D0+ABS(HAZIP)))
2279      &      GOTO 560
2280           ENDIF
2281           IF(MAZIC.NE.0) THEN
2282             IF(MAZIC.EQ.N+2) CAD=-CAD
2283             IF((1D0-HAZIC)*(1D0-HAZIC*CAD)/(1D0+HAZIC**2-2D0*HAZIC*CAD)
2284      &      .LT.PYR(0)) GOTO 560
2285           ENDIF
2286         ENDIF
2287       ENDIF
2288
2289 C...Azimuthal anisotropy due to interference with initial state partons.
2290       IF(MOD(MIIS,2).EQ.1.AND.IGM.EQ.NS+1.AND.(K(N+1,2).EQ.21.OR.
2291      &K(N+2,2).EQ.21)) THEN
2292         III=IM-NS-1
2293         IF(ISII(III).GE.1) THEN
2294           IAZIID=N+1
2295           IF(K(N+1,2).NE.21) IAZIID=N+2
2296           IF(K(N+1,2).EQ.21.AND.K(N+2,2).EQ.21.AND.
2297      &    P(N+1,4).GT.P(N+2,4)) IAZIID=N+2
2298           THEIID=PYANGL(P(IAZIID,3),SQRT(P(IAZIID,1)**2+P(IAZIID,2)**2))
2299           IF(III.EQ.2) THEIID=PARU(1)-THEIID
2300           PHIIID=PYANGL(P(IAZIID,1),P(IAZIID,2))
2301           HAZII=MIN(0.95D0,THEIID/THEIIS(III,ISII(III)))
2302           CAD=COS(PHIIID-PHIIIS(III,ISII(III)))
2303           PHIREL=ABS(PHIIID-PHIIIS(III,ISII(III)))
2304           IF(PHIREL.GT.PARU(1)) PHIREL=PARU(2)-PHIREL
2305           IF((1D0-HAZII)*(1D0-HAZII*CAD)/(1D0+HAZII**2-2D0*HAZII*CAD)
2306      &    .LT.PYR(0)) GOTO 560
2307         ENDIF
2308       ENDIF
2309
2310 C...Continue loop over partons that may branch, until none left.
2311       IF(IGM.GE.0) K(IM,1)=14
2312       N=N+NEP
2313       NEP=2
2314       IF(N.GT.MSTU(4)-MSTU(32)-10) THEN
2315         CALL PYERRM(11,'(PYSHOW:) no more memory left in PYJETS')
2316         IF(MSTU(21).GE.1) N=NS
2317         IF(MSTU(21).GE.1) RETURN
2318       ENDIF
2319       GOTO 290
2320
2321 C...Set information on imagined shower initiator.
2322   600 IF(NPA.GE.2) THEN
2323         K(NS+1,1)=11
2324         K(NS+1,2)=94
2325         K(NS+1,3)=IP1
2326         IF(IP2.GT.0.AND.IP2.LT.IP1) K(NS+1,3)=IP2
2327         K(NS+1,4)=NS+2
2328         K(NS+1,5)=NS+1+NPA
2329         IIM=1
2330       ELSE
2331         IIM=0
2332       ENDIF
2333
2334 C...Reconstruct string drawing information.
2335       DO 610 I=NS+1+IIM,N
2336         KQ=KCHG(PYCOMP(K(I,2)),2)
2337         IF(K(I,1).LE.10.AND.K(I,2).EQ.22) THEN
2338           K(I,1)=1
2339         ELSEIF(K(I,1).LE.10.AND.IABS(K(I,2)).GE.11.AND.
2340      &    IABS(K(I,2)).LE.18) THEN
2341           K(I,1)=1
2342         ELSEIF(K(I,1).LE.10) THEN
2343           K(I,4)=MSTU(5)*(K(I,4)/MSTU(5))
2344           K(I,5)=MSTU(5)*(K(I,5)/MSTU(5))
2345         ELSEIF(K(MOD(K(I,4),MSTU(5))+1,2).NE.22) THEN
2346           ID1=MOD(K(I,4),MSTU(5))
2347           IF(KQ.EQ.1.AND.K(I,2).GT.0) ID1=MOD(K(I,4),MSTU(5))+1
2348           IF(KQ.EQ.2.AND.(K(ID1,2).EQ.21.OR.K(ID1+1,2).EQ.21).AND.
2349      &    PYR(0).GT.0.5D0) ID1=MOD(K(I,4),MSTU(5))+1
2350           ID2=2*MOD(K(I,4),MSTU(5))+1-ID1
2351           K(I,4)=MSTU(5)*(K(I,4)/MSTU(5))+ID1
2352           K(I,5)=MSTU(5)*(K(I,5)/MSTU(5))+ID2
2353           K(ID1,4)=K(ID1,4)+MSTU(5)*I
2354           K(ID1,5)=K(ID1,5)+MSTU(5)*ID2
2355           K(ID2,4)=K(ID2,4)+MSTU(5)*ID1
2356           K(ID2,5)=K(ID2,5)+MSTU(5)*I
2357         ELSE
2358           ID1=MOD(K(I,4),MSTU(5))
2359           ID2=ID1+1
2360           K(I,4)=MSTU(5)*(K(I,4)/MSTU(5))+ID1
2361           K(I,5)=MSTU(5)*(K(I,5)/MSTU(5))+ID1
2362           IF(KQ.EQ.1.OR.K(ID1,1).GE.11) THEN
2363             K(ID1,4)=K(ID1,4)+MSTU(5)*I
2364             K(ID1,5)=K(ID1,5)+MSTU(5)*I
2365           ELSE
2366             K(ID1,4)=0
2367             K(ID1,5)=0
2368           ENDIF
2369           K(ID2,4)=0
2370           K(ID2,5)=0
2371         ENDIF
2372   610 CONTINUE
2373
2374 C...Transformation from CM frame.
2375       IF(NPA.EQ.1) THEN
2376         THE=PYANGL(P(IPA(1),3),SQRT(P(IPA(1),1)**2+P(IPA(1),2)**2))
2377         PHI=PYANGL(P(IPA(1),1),P(IPA(1),2))
2378         MSTU(33)=1
2379         CALL PYROBO(NS+1,N,THE,PHI,0D0,0D0,0D0)
2380       ELSEIF(NPA.EQ.2) THEN
2381         BEX=PS(1)/PS(4)
2382         BEY=PS(2)/PS(4)
2383         BEZ=PS(3)/PS(4)
2384         GA=PS(4)/PS(5)
2385         GABEP=GA*(GA*(BEX*P(IPA(1),1)+BEY*P(IPA(1),2)+BEZ*P(IPA(1),3))
2386      &  /(1D0+GA)-P(IPA(1),4))
2387         THE=PYANGL(P(IPA(1),3)+GABEP*BEZ,SQRT((P(IPA(1),1)
2388      &  +GABEP*BEX)**2+(P(IPA(1),2)+GABEP*BEY)**2))
2389         PHI=PYANGL(P(IPA(1),1)+GABEP*BEX,P(IPA(1),2)+GABEP*BEY)
2390         MSTU(33)=1
2391         CALL PYROBO(NS+1,N,THE,PHI,BEX,BEY,BEZ)
2392       ELSE
2393         CALL PYROBO(IPA(1),IPA(NPA),0D0,0D0,PS(1)/PS(4),PS(2)/PS(4),
2394      &  PS(3)/PS(4))
2395         MSTU(33)=1
2396         CALL PYROBO(NS+1,N,0D0,0D0,PS(1)/PS(4),PS(2)/PS(4),PS(3)/PS(4))
2397       ENDIF
2398
2399 C...Decay vertex of shower.
2400       DO 630 I=NS+1,N
2401         DO 620 J=1,5
2402           V(I,J)=V(IP1,J)
2403   620   CONTINUE
2404   630 CONTINUE
2405
2406 C...Delete trivial shower, else connect initiators.
2407       IF(N.LE.NS+NPA+IIM) THEN
2408         N=NS
2409       ELSE
2410         DO 640 IP=1,NPA
2411           K(IPA(IP),1)=14
2412           K(IPA(IP),4)=K(IPA(IP),4)+NS+IIM+IP
2413           K(IPA(IP),5)=K(IPA(IP),5)+NS+IIM+IP
2414           K(NS+IIM+IP,3)=IPA(IP)
2415           IF(IIM.EQ.1.AND.MSTU(16).NE.2) K(NS+IIM+IP,3)=NS+1
2416           IF(K(NS+IIM+IP,1).NE.1) THEN
2417             K(NS+IIM+IP,4)=MSTU(5)*IPA(IP)+K(NS+IIM+IP,4)
2418             K(NS+IIM+IP,5)=MSTU(5)*IPA(IP)+K(NS+IIM+IP,5)
2419           ENDIF
2420   640   CONTINUE
2421       ENDIF
2422
2423       RETURN
2424       END
2425
2426
2427       SUBROUTINE QPYGIN(X0,Y0,Z0,T0)
2428 C     NOT TO BE TOUCHED BY THE USER:
2429 C     IT SETS THE INITIAL POSITION AND TIME OF THE
2430 C     PARENT BRANCHING PARTON (X, Y, Z, T, IN FM) IN THE CENTER-OF-MASS
2431 C     FRAME OF THE HARD COLLISION (IF APPLICABLE FOR THE TYPE OF EVENTS
2432 C     YOU ARE SIMULATING). INFORMATION ABOUT THE BOOST AND ROTATION IS
2433 C     CONTAINED IN THE IN COMMON QPLT BELOW.
2434       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
2435 C     NOW THE COMMON CONTAINING THE VALUES OF THE TWO ANGLES AND THREE BOSST
2436 C     PARAMETERS USED, IN PYSHOW, TO CHANGE THROUGH PYROBO FROM THE
2437 C     CENTER-OF-MASS OF THE COLLISION TO THE CENTER-OF-MASS OF THE HARD
2438 C     SCATTERING. THEY ARE THE ENTRIES THREE TO SEVEN IN ROUTINE PYROBO.
2439 C     XX, YY, ZZ, TT COMING FROM QPYGIN0 IN THE CMS OF THE COLLISION, GENERATED
2440 C     ONCE PER NUCLEON-NUCLEON COLLISION.
2441       COMMON/TOQPYGIN/XX,YY,ZZ,TT
2442       COMMON/QPLT/AA1,AA2,BBX,BBY,BBZ
2443 C     Boost and rotation.
2444       call qpyrobo(xx,yy,zz,tt,0.d0,0.d0,bbx,bby,bbz,x1,y1,z1,t1)
2445       call qpyrobo(x1,y1,z1,t1,0.d0,aa2,0.d0,0.d0,0.d0,x2,y2,z2,t2)
2446       call qpyrobo(x2,y2,z2,t2,aa1,0.d0,0.d0,0.d0,0.d0,x0,y0,z0,t0)
2447 C
2448       RETURN
2449       END
2450
2451
2452
2453       SUBROUTINE QPYGIN0
2454 C     USER-DEFINED ROUTINE: IT SETS THE INITIAL POSITION AND TIME OF THE
2455 C     PARENT BRANCHING PARTON (X, Y, Z, T, IN FM) IN THE CENTER-OF-MASS
2456 C     FRAME OF THE COLLISION.
2457 C     IT SHOULD BE CALLED IN THE MAIN PROGRAM, ONCE PER NUCLEON-NUCLEON
2458 C     COLLISION (PER PP COLLISION IF YOU ARE SIMPLY RUNNING PP).
2459       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
2460       COMMON/TOQPYGIN/XX,YY,ZZ,TT
2461 C     Example: this is to be set by the user e.g. as coming from the overlap
2462 C     of nuclear profile functions (number of binary nucleon-nucleon
2463 C     collisions).
2464       call GetRandomXY(xrang,yrang)
2465       xin=xrang ! fm
2466       yin=yrang ! fm
2467       call savexy(xin, yin)
2468       zin=0.d0
2469       tin=0.d0
2470 C     Passing to the common block.
2471       xx=xin
2472       yy=yin
2473       zz=zin
2474       tt=tin
2475 c
2476 c      print*,"initial coordinates", xx,yy,zz,tt
2477       RETURN
2478       END
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489 C
2490       SUBROUTINE QPYGEO(x,y,z,t,bx,by,bz,qhl,oc)
2491 C     USER-DEFINED ROUTINE:
2492 C     The values of qhatL and omegac have to be computed
2493 C     by the user, using his preferred medium model, in
2494 C     this routine, which takes as input the position
2495 C     x,y,z,t (in fm) of the parton to branch, the trajectory
2496 C     defined by the three-vector bx,by,bz (in units of c),
2497 C     (all values in the center-of-mass frame of the
2498 C     hard collision), and returns the value of qhatL
2499 C     (in GeV**2) and omegac (in GeV).
2500       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
2501 C     NOW THE COMMON CONTAINING THE VALUES OF THE TWO ANGLES AND THREE BOSST
2502 C     PARAMETERS USED, IN PYSHOW, TO CHANGE THROUGH PYROBO FROM THE
2503 C     CENTER-OF-MASS OF THE COLLISION TO THE CENTER-OF-MASS OF THE HARD
2504 C     SCATTERING. THEY ARE THE ENTRIES THREE TO SEVEN IN ROUTINE PYROBO.
2505       COMMON/QPLT/AA1,AA2,BBX,BBY,BBZ
2506       COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
2507       qhat=parj(198)
2508       xl=parj(199)
2509       bimp=parj(197)
2510 c     Here we give five options for the geometry of the medium:
2511
2512 c$$$cforalice+
2513 c$$$     (0) we call routine CalculateI0I1 in AliFastGlauber. Given the position
2514 c$$$     of the parton in the reaction plane (x,y), the direction in the
2515 c$$$     reaction plane phi=atan(py/px) and the impact parameter of the
2516 c$$$     collision bimp, it gives back the transverse path length to the
2517 c$$$     "end" of the medium and the integrated qhat along that path length.
2518 c$$$     See the seter for this option in Configqpythia.C(one can set the
2519 c$$$     value of xkscale by doing SetQhat(xkscale), with xkscale in fm).
2520 c$$$     The set value is passed here through the pythia free parameter parj(198).
2521
2522
2523       xkscale=parj(198)
2524       ellcut=20.d0
2525       xlcero=0.d0
2526       xlone=0.d0
2527
2528       call qpyrobo(x,y,z,t,-aa1,-aa2,-bbx,-bby,-bbz,xout,
2529      + yout,zout,tout)
2530
2531       call qpyrobo(bx,by,bz,1.d0,-aa1,-aa2,-bbx,-bby,-bbz,
2532      + bx1,by1,bz1,bt1)
2533
2534
2535       phi=datan2(by1,bx1)
2536       phia=phi
2537       bimpa=bimp
2538       ellcuta=ellcut
2539       xa=xout
2540       ya=yout
2541       call CalculateI0I1(xlcero,xlone,bimpa,xa,ya,phia,ellcuta)
2542       if(xlcero.eq.0.d0) then
2543            xlp=0.d0
2544            qhl=0.d0
2545       else
2546       xlp=2.d0*xlone/xlcero
2547       qhl=0.1973d0*0.1973d0*xlcero*xkscale
2548       call savei0i1(xlcero, xlone)
2549       endif
2550
2551
2552 c$$$cforalice-
2553 c     To use any of these folowing 1,2,3 or 4 options the user should specify
2554 c     a constant value for the transport coefficient and an initial in medium length.
2555 c     This can be done in the user Config file by setting: SetQhat(qhat), with qhat in
2556 c     GeV2/fm and SetLength(xl), with xl in fm. Those values are passed here through
2557 c     pythia free parameters parj(198) and parj(199).
2558
2559 c     (1) to fix the length to the initial value, uncomment the next three lines
2560 c     and comment the other definitions of xlp and qhl above and below.
2561 c      xlp=xl
2562 c      if (xlp .lt. 0.d0) xlp=0.d0
2563 c      qhl=xlp*qhat ! GeV**2
2564 c        print*, xlp,qhl
2565 c     (2) simplest ansatz: for an initial parton along the z-axis (approximate)
2566 c      starting in the center of a medium (-xl,+xl) along the z-axis
2567 c       if (bz .gt. 0.d0) then
2568 c         xlp=xl-z
2569 c       else
2570 c         xlp=xl+z
2571 c       endif
2572 c      if (xlp .gt. (2.d0*xl)) xlp=2.d0*xl
2573 c      if (xlp .lt. 0.d0) xlp=0.d0
2574 c      qhl=xlp*qhat ! GeV**2
2575
2576 c     (3) for a parton at midrapidity inside a cylinder (approximate)
2577 c      xlp=xl-dsqrt(x*x+y*y)
2578 c      if (xlp .lt. 0.d0) xlp=0.d0
2579 c      qhl=xlp*qhat ! GeV**2
2580
2581 c     (4) for a brick defined by planes (x,y,0) and (x,y,xl), comment
2582 c     the previous lines and uncomment lines between the comment 'brick'.
2583 c     brick+
2584 c       if (z .ge. 0.d0 .and. z .le. xl)
2585 c     >    then
2586 c            if (bz .gt. 0.d0) then
2587 c               ttpp=(xl-z)/bz
2588 c               xlp=dsqrt((bx*ttpp)**2.d0+(by*ttpp)**2.d0+
2589 c     >             (xl-z)**2.d0)
2590 c            else
2591 c               ttpp=z/dabs(bz)
2592 c               xlp=dsqrt((bx*ttpp)**2.d0+(by*ttpp)**2.d0+
2593 c     >             (z)**2.d0)
2594 c            endif
2595 c         elseif (z .lt. 0.d0) then
2596 c           if (bz .lt. 0.d0) then
2597 c              xlp=0.d0
2598 c           else
2599 c              ttpp1=-z/bz
2600 c              ttpp2=(xl-z)/bz
2601 c              xxpp1=x+bx*ttpp1
2602 c              xxpp2=x+bx*ttpp2
2603 c              yypp1=y+by*ttpp1
2604 c              yypp2=y+by*ttpp2
2605 c              xlp=dsqrt((xxpp1-xxpp2)**2.d0+(yypp1-yypp2)**2.d0+
2606 c     >                  xl**2.d0)
2607 c           endif
2608 c         elseif (z .gt. xl) then
2609 c           if (bz .gt. 0.d0) then
2610 c              xlp=0.d0
2611 c           else
2612 c              ttpp1=z/dabs(bz)
2613 c              ttpp2=(-xl+z)/dabs(bz)
2614 c              xxpp1=x+bx*ttpp1
2615 c              xxpp2=x+bx*ttpp2
2616 c              yypp1=y+by*ttpp1
2617 c              yypp2=y+by*ttpp2
2618 c              xlp=dsqrt((xxpp1-xxpp2)**2.d0+(yypp1-yypp2)**2.d0+
2619 c     >                  xl**2.d0)
2620 c           endif
2621 c         endif
2622 c      if (xlp .lt. 0.d0) xlp=0.d0
2623 c      qhl=xlp*qhat ! GeV**2
2624 c     brick-
2625
2626       oc=0.5d0*qhl*xlp/0.1973d0 ! GeV
2627       RETURN
2628       END