HERWIG/src/hwsval.f

   1
   2 CDECK  ID>, HWSVAL.
   3
   4 *CMZ :-        -26/04/91  10.18.58  by  Bryan Webber
   5
   6 *-- Author :    Bryan Webber
   7
   8 C-----------------------------------------------------------------------
   9
  10       FUNCTION HWSVAL(ID)
  11
  12 C-----------------------------------------------------------------------
  13
  14 C     TRUE FOR VALENCE PARTON ID IN INCOMING HADRON INHAD
  15
  16 C-----------------------------------------------------------------------
  17
  18       INCLUDE 'HERWIG61.INC'
  19
  20       INTEGER ID,IDHAD
  21
  22       LOGICAL HWSVAL
  23
  24       HWSVAL=.FALSE.
  25
  26       IDHAD=IDHW(INHAD)
  27
  28       IF (IDHAD.EQ.73.OR.IDHAD.EQ.75) THEN
  29
  30         IF (ID.EQ.1.OR.ID.EQ.2) HWSVAL=.TRUE.
  31
  32       ELSEIF (IDHAD.EQ.91.OR.IDHAD.EQ.93) THEN
  33
  34         IF (ID.EQ.7.OR.ID.EQ.8) HWSVAL=.TRUE.
  35
  36       ELSEIF (IDHAD.EQ.30) THEN
  37
  38         IF (ID.EQ.1.OR.ID.EQ.8) HWSVAL=.TRUE.
  39
  40       ELSEIF (IDHAD.EQ.38) THEN
  41
  42         IF (ID.EQ.2.OR.ID.EQ.7) HWSVAL=.TRUE.
  43
  44       ELSEIF (IDHAD.EQ.59) THEN
  45
  46         IF (ID.LT.6.OR.(ID.GT.6.AND.ID.LT.12)) HWSVAL=.TRUE.
  47
  48       ELSEIF (IDHAD.EQ.71.OR.IDHAD.EQ.72) THEN
  49
  50         IF (ID.EQ.13) HWSVAL=.TRUE.
  51
  52       ELSE
  53
  54         CALL HWWARN('HWSVAL',100,*999)
  55
  56       ENDIF
  57
  58   999 END
  59
  60 CDECK  ID>, HWUAEM.
  61
  62 *CMZ :-        -23/08/94  13.22.29  by  Mike Seymour
  63
  64 *-- Author :    Ian Knowles
  65
  66 C-----------------------------------------------------------------------
  67
  68       FUNCTION HWUAEM(Q2)
  69
  70 C-----------------------------------------------------------------------
  71
  72 C     Running electromagnetic coupling constant.
  73
  74 C     See R. Kleiss et al.: CERN yellow report 89-08, vol.3 p.129
  75
  76 C     Hadronic component from: H. Burkhardt et al.: Z. Phys C43 (89) 497
  77
  78 C-----------------------------------------------------------------------
  79
  80       INCLUDE 'HERWIG61.INC'
  81
  82       DOUBLE PRECISION HWUAEM,HWUAER,Q2,EPS,A1,B1,C1,A2,B2,C2,A3,B3,C3,
  83
  84      & A4,B4,C4,AEMPI,EEL2,EMU2,ETAU2,ETOP2,REPIGG,X
  85
  86       LOGICAL FIRST
  87
  88       EXTERNAL HWUAER
  89
  90       SAVE FIRST,AEMPI,EEL2,EMU2,ETAU2,ETOP2
  91
  92       PARAMETER (EPS=1.D-6)
  93
  94       DATA A1,B1,C1/0.0    ,0.00835,1.000/
  95
  96       DATA A2,B2,C2/0.0    ,0.00238,3.927/
  97
  98       DATA A3,B3,C3/0.00165,0.00299,1.000/
  99
 100       DATA A4,B4,C4/0.00221,0.00293,1.000/
 101
 102       DATA FIRST/.TRUE./
 103
 104       IF (FIRST) THEN
 105
 106          AEMPI=ALPHEM/(THREE*PIFAC)
 107
 108          EEL2 =RMASS(121)**2
 109
 110          EMU2 =RMASS(123)**2
 111
 112          ETAU2=RMASS(125)**2
 113
 114          ETOP2=RMASS(6)**2
 115
 116          FIRST=.FALSE.
 117
 118       ENDIF
 119
 120       IF (ABS(Q2).LT.EPS) THEN
 121
 122           HWUAEM=ALPHEM
 123
 124           RETURN
 125
 126       ENDIF
 127
 128 C Leptonic component
 129
 130       REPIGG=AEMPI*(HWUAER(EEL2/Q2)+HWUAER(EMU2/Q2)+HWUAER(ETAU2/Q2))
 131
 132 C Hadronic component from light quarks
 133
 134       X=ABS(Q2)
 135
 136       IF (X.LT.9.D-2) THEN
 137
 138           REPIGG=REPIGG+A1+B1*LOG(ONE+C1*X)
 139
 140       ELSEIF (X.LT.9.D0) THEN
 141
 142           REPIGG=REPIGG+A2+B2*LOG(ONE+C2*X)
 143
 144       ELSEIF (X.LT.1.D4) THEN
 145
 146           REPIGG=REPIGG+A3+B3*LOG(ONE+C3*X)
 147
 148       ELSE
 149
 150           REPIGG=REPIGG+A4+B4*LOG(ONE+C4*X)
 151
 152       ENDIF
 153
 154 C Top Contribution
 155
 156       REPIGG=REPIGG+AEMPI*HWUAER(ETOP2/Q2)
 157
 158       HWUAEM=ALPHEM/(ONE-REPIGG)
 159
 160       RETURN
 161
 162       END