HIJING/hijing1_36/ar3jet.F

   1 * $Id$
   2
   3
   4         SUBROUTINE AR3JET(S,X1,X3,JL)
   5 C
   6 #include "hiparnt.inc"
   7 #include "lujets_hijing.inc"
   8         SAVE
   9 C
  10         C=1./3.
  11         IF(K(JL,2).NE.21 .AND. K(JL+1,2).NE.21) C=8./27.
  12         EXP1=3
  13         EXP3=3
  14         IF(K(JL,2).NE.21) EXP1=2
  15         IF(K(JL+1,2).NE.21) EXP3=2
  16         A=0.24**2/S
  17         YMA=ALOG(.5/SQRT(A)+SQRT(.25/A-1))
  18         D=4.*C*YMA
  19         SM1=P(JL,5)**2/S
  20         SM3=P(JL+1,5)**2/S
  21         XT2M=(1.-2.*SQRT(SM1)+SM1-SM3)*(1.-2.*SQRT(SM3)-SM1+SM3)
  22         XT2M=MIN(.25,XT2M)
  23         NTRY=0
  24 1       IF(NTRY.EQ.5000) THEN
  25                 X1=.5*(2.*SQRT(SM1)+1.+SM1-SM3)
  26                 X3=.5*(2.*SQRT(SM3)+1.-SM1+SM3)
  27                 RETURN
  28         ENDIF
  29         NTRY=NTRY+1
  30
  31         XT2=A*(XT2M/A)**(RLU_HIJING(0)**(1./D))
  32
  33         YMAX=ALOG(.5/SQRT(XT2)+SQRT(.25/XT2-1.))
  34         Y=(2.*RLU_HIJING(0)-1.)*YMAX
  35         X1=1.-SQRT(XT2)*EXP(Y)
  36         X3=1.-SQRT(XT2)*EXP(-Y)
  37         X2=2.-X1-X3
  38         NEG=0
  39         IF(K(JL,2).NE.21 .OR. K(JL+1,2).NE.21) THEN
  40         IF((1.-X1)*(1.-X2)*(1.-X3)-X2*SM1*(1.-X1)-X2*SM3*(1.-X3).
  41      &  LE.0..OR.X1.LE.2.*SQRT(SM1)-SM1+SM3.OR.X3.LE.2.*SQRT(SM3)
  42      &  -SM3+SM1) NEG=1
  43         X1=X1+SM1-SM3
  44         X3=X3-SM1+SM3
  45         ENDIF
  46         IF(NEG.EQ.1) GOTO 1
  47
  48         FG=2.*YMAX*C*(X1**EXP1+X3**EXP3)/D
  49         XT2M=XT2
  50         IF(FG.LT.RLU_HIJING(0)) GOTO 1
  51
  52         RETURN
  53         END