HERWIG/src/hwbsul.f

   1
   2 CDECK  ID>, HWBSUL.
   3
   4 *CMZ :-        -13/07/92  20.15.54  by  Mike Seymour
   5
   6 *-- Author :    Mike Seymour
   7
   8 C-----------------------------------------------------------------------
   9
  10       FUNCTION HWBSUL(Z)
  11
  12 C-----------------------------------------------------------------------
  13
  14 C     LOGARITHMIC PART OF INTEGRAND IN EXPONENT OF SUDAKOV FORM FACTOR.
  15
  16 C     THE SECOND ORDER ALPHAS CASE COMES FROM CONVERTING INTEGRAL OVER
  17
  18 C     Q^2 INTO ONE OVER ALPHAS, WITH FLAVOUR THRESHOLDS.
  19
  20 C-----------------------------------------------------------------------
  21
  22       INCLUDE 'HERWIG61.INC'
  23
  24       DOUBLE PRECISION HWBSUL,HWUALF,Z,QRAT,QLAM,U,AL,BL,QNOW,QMIN,
  25
  26      & BET(6),BEP(6),MUMI(6),MUMA(6),ALMI(6),ALMA(6),FINT(6),ALFINT,
  27
  28      & MUMIN,MUMAX,ALMIN,ALMAX
  29
  30       INTEGER NF
  31
  32       LOGICAL FIRST
  33
  34       EXTERNAL HWUALF
  35
  36       SAVE FIRST,BET,BEP,MUMI,MUMA
  37
  38       COMMON/HWSINT/QRAT,QLAM
  39
  40       DATA FIRST/.TRUE./
  41
  42       ALFINT(AL,BL)=1/BET(NF)*
  43
  44      &        LOG(BL/(AL*(1+BEP(NF)*BL))*(1+BEP(NF)*AL))
  45
  46       HWBSUL=0
  47
  48       U=1.-Z
  49
  50       IF (SUDORD.EQ.1) THEN
  51
  52         AL=LOG(QRAT*Z)
  53
  54         BL=LOG(QLAM*U*Z)
  55
  56         HWBSUL=LOG(1.-AL/BL)
  57
  58       ELSE
  59
  60         IF (FIRST) THEN
  61
  62           DO 10 NF=3,6
  63
  64             BET(NF)=(11*CAFAC-2*NF)/(12*PIFAC)
  65
  66             BEP(NF)=(17*CAFAC**2-(5*CAFAC+3*CFFAC)*NF)/(24*PIFAC**2)
  67
  68      &              /BET(NF)
  69
  70             IF (NF.EQ.3) THEN
  71
  72               MUMI(3)=0
  73
  74               ALMI(3)=1D30
  75
  76             ELSE
  77
  78               MUMI(NF)=RMASS(NF)
  79
  80               ALMI(NF)=HWUALF(1,MUMI(NF))
  81
  82             ENDIF
  83
  84             IF (NF.EQ.6) THEN
  85
  86               MUMA(NF)=1D30
  87
  88               ALMA(NF)=0
  89
  90             ELSE
  91
  92               MUMA(NF)=RMASS(NF+1)
  93
  94               ALMA(NF)=HWUALF(1,MUMA(NF))
  95
  96             ENDIF
  97
  98             IF (NF.NE.3.AND.NF.NE.6) FINT(NF)=ALFINT(ALMI(NF),ALMA(NF))
  99
 100  10       CONTINUE
 101
 102           FIRST=.FALSE.
 103
 104         ENDIF
 105
 106         QNOW=QLAM*QCDL3
 107
 108         QMIN=QNOW/QRAT
 109
 110         MUMIN=  U*QMIN
 111
 112         MUMAX=Z*U*QNOW
 113
 114         IF (MUMAX.LE.MUMIN) RETURN
 115
 116         ALMIN=HWUALF(1,MUMIN)
 117
 118         ALMAX=HWUALF(1,MUMAX)
 119
 120         NF=3
 121
 122  20     IF (MUMIN.GT.MUMA(NF)) THEN
 123
 124           NF=NF+1
 125
 126           GOTO 20
 127
 128         ENDIF
 129
 130         IF (MUMAX.LT.MUMA(NF)) THEN
 131
 132           HWBSUL=ALFINT(ALMIN,ALMAX)
 133
 134         ELSE
 135
 136           HWBSUL=ALFINT(ALMIN,ALMA(NF))
 137
 138           NF=NF+1
 139
 140  30       IF (MUMAX.GT.MUMA(NF)) THEN
 141
 142             HWBSUL=HWBSUL+FINT(NF)
 143
 144             NF=NF+1
 145
 146             GOTO 30
 147
 148           ENDIF
 149
 150           HWBSUL=HWBSUL+ALFINT(ALMI(NF),ALMAX)
 151
 152         ENDIF
 153
 154         HWBSUL=HWBSUL*BET(5)
 155
 156       ENDIF
 157
 158       END