HERWIG/src/hwdthr.f

   1
   2 CDECK  ID>, HWDTHR.
   3
   4 *CMZ :-        -26/04/91  14.55.44  by  Federico Carminati
   5
   6 *-- Author :    Bryan Webber
   7
   8 C-----------------------------------------------------------------------
   9
  10       SUBROUTINE HWDTHR(P0,P1,P2,P3,WEIGHT)
  11
  12 C-----------------------------------------------------------------------
  13
  14 C     GENERATES THREE-BODY DECAY 0->1+2+3 DISTRIBUTED
  15
  16 C     ACCORDING TO PHASE SPACE * WEIGHT
  17
  18 C-----------------------------------------------------------------------
  19
  20       DOUBLE PRECISION HWR,HWRUNI,A,B,C,D,AA,BB,CC,DD,EE,FF,PP,QQ,WW,
  21
  22      & RR,PCM1,PC23,WEIGHT,P0(5),P1(5),P2(5),P3(5),P23(5),TWO
  23
  24       EXTERNAL HWR,HWRUNI,WEIGHT
  25
  26       PARAMETER (TWO=2.D0)
  27
  28       A=P0(5)+P1(5)
  29
  30       B=P0(5)-P1(5)
  31
  32       C=P2(5)+P3(5)
  33
  34       IF (B.LT.C) CALL HWWARN('HWDTHR',100,*999)
  35
  36       D=ABS(P2(5)-P3(5))
  37
  38       AA=A*A
  39
  40       BB=B*B
  41
  42       CC=C*C
  43
  44       DD=D*D
  45
  46       EE=(B-C)*(A-D)
  47
  48       A=0.5*(AA+BB)
  49
  50       B=0.5*(CC+DD)
  51
  52       C=4./(A-B)**2
  53
  54 C
  55
  56 C  CHOOSE MASS OF SUBSYSTEM 23 WITH PRESCRIBED DISTRIBUTION
  57
  58 C
  59
  60    10 FF=HWRUNI(0,BB,CC)
  61
  62       PP=(AA-FF)*(BB-FF)
  63
  64       QQ=(CC-FF)*(DD-FF)
  65
  66       WW=WEIGHT(FF,A,B,C)**2
  67
  68       RR=EE*FF*HWR()
  69
  70       IF (PP*QQ*WW.LT.RR*RR) GOTO 10
  71
  72 C
  73
  74 C  FF IS MASS SQUARED OF SUBSYSTEM 23.
  75
  76 C
  77
  78 C  DO 2-BODY DECAYS 0->1+23, 23->2+3
  79
  80 C
  81
  82       P23(5)=SQRT(FF)
  83
  84       PCM1=SQRT(PP)*0.5/P0(5)
  85
  86       PC23=SQRT(QQ)*0.5/P23(5)
  87
  88       CALL HWDTWO(P0,P1,P23,PCM1,TWO,.TRUE.)
  89
  90       CALL HWDTWO(P23,P2,P3,PC23,TWO,.TRUE.)
  91
  92   999 END
  93
  94 CDECK  ID>, HWDTOP.
  95
  96 *CMZ :-        -09/12/92  11.03.46  by  Bryan Webber
  97
  98 *-- Author :    Bryan Webber
  99
 100 C-----------------------------------------------------------------------
 101
 102       SUBROUTINE HWDTOP(DECAY)
 103
 104 C-----------------------------------------------------------------------
 105
 106 C     DECIDES WHETHER TO DO TOP QUARK DECAY BEFORE HADRONIZATION
 107
 108 C-----------------------------------------------------------------------
 109
 110       INCLUDE 'HERWIG61.INC'
 111
 112       LOGICAL DECAY
 113
 114       DECAY=RMASS(6).GT.130D0
 115
 116       END