CDECK  ID>, HWSVAL.

*CMZ :-        -26/04/91  10.18.58  by  Bryan Webber

*-- Author :    Bryan Webber

C-----------------------------------------------------------------------

      FUNCTION HWSVAL(ID)

C-----------------------------------------------------------------------

C     TRUE FOR VALENCE PARTON ID IN INCOMING HADRON INHAD

C-----------------------------------------------------------------------

      INCLUDE 'HERWIG61.INC'

      INTEGER ID,IDHAD

      LOGICAL HWSVAL

      HWSVAL=.FALSE.

      IDHAD=IDHW(INHAD)

      IF (IDHAD.EQ.73.OR.IDHAD.EQ.75) THEN

        IF (ID.EQ.1.OR.ID.EQ.2) HWSVAL=.TRUE.

      ELSEIF (IDHAD.EQ.91.OR.IDHAD.EQ.93) THEN

        IF (ID.EQ.7.OR.ID.EQ.8) HWSVAL=.TRUE.

      ELSEIF (IDHAD.EQ.30) THEN

        IF (ID.EQ.1.OR.ID.EQ.8) HWSVAL=.TRUE.

      ELSEIF (IDHAD.EQ.38) THEN

        IF (ID.EQ.2.OR.ID.EQ.7) HWSVAL=.TRUE.

      ELSEIF (IDHAD.EQ.59) THEN

        IF (ID.LT.6.OR.(ID.GT.6.AND.ID.LT.12)) HWSVAL=.TRUE.

      ELSEIF (IDHAD.EQ.71.OR.IDHAD.EQ.72) THEN

        IF (ID.EQ.13) HWSVAL=.TRUE.

      ELSE

        CALL HWWARN('HWSVAL',100,*999)

      ENDIF

  999 END

CDECK  ID>, HWUAEM.

*CMZ :-        -23/08/94  13.22.29  by  Mike Seymour

*-- Author :    Ian Knowles

C-----------------------------------------------------------------------

      FUNCTION HWUAEM(Q2)

C-----------------------------------------------------------------------

C     Running electromagnetic coupling constant.

C     See R. Kleiss et al.: CERN yellow report 89-08, vol.3 p.129

C     Hadronic component from: H. Burkhardt et al.: Z. Phys C43 (89) 497

C-----------------------------------------------------------------------

      INCLUDE 'HERWIG61.INC'

      DOUBLE PRECISION HWUAEM,HWUAER,Q2,EPS,A1,B1,C1,A2,B2,C2,A3,B3,C3,

     & A4,B4,C4,AEMPI,EEL2,EMU2,ETAU2,ETOP2,REPIGG,X

      LOGICAL FIRST

      EXTERNAL HWUAER

      SAVE FIRST,AEMPI,EEL2,EMU2,ETAU2,ETOP2

      PARAMETER (EPS=1.D-6)

      DATA A1,B1,C1/0.0    ,0.00835,1.000/

      DATA A2,B2,C2/0.0    ,0.00238,3.927/

      DATA A3,B3,C3/0.00165,0.00299,1.000/

      DATA A4,B4,C4/0.00221,0.00293,1.000/

      DATA FIRST/.TRUE./

      IF (FIRST) THEN

         AEMPI=ALPHEM/(THREE*PIFAC)

         EEL2 =RMASS(121)**2

         EMU2 =RMASS(123)**2

         ETAU2=RMASS(125)**2

         ETOP2=RMASS(6)**2

         FIRST=.FALSE.

      ENDIF

      IF (ABS(Q2).LT.EPS) THEN

          HWUAEM=ALPHEM

          RETURN

      ENDIF

C Leptonic component

      REPIGG=AEMPI*(HWUAER(EEL2/Q2)+HWUAER(EMU2/Q2)+HWUAER(ETAU2/Q2))

C Hadronic component from light quarks

      X=ABS(Q2)

      IF (X.LT.9.D-2) THEN

          REPIGG=REPIGG+A1+B1*LOG(ONE+C1*X)

      ELSEIF (X.LT.9.D0) THEN

          REPIGG=REPIGG+A2+B2*LOG(ONE+C2*X)

      ELSEIF (X.LT.1.D4) THEN

          REPIGG=REPIGG+A3+B3*LOG(ONE+C3*X)

      ELSE

          REPIGG=REPIGG+A4+B4*LOG(ONE+C4*X)

      ENDIF

C Top Contribution

      REPIGG=REPIGG+AEMPI*HWUAER(ETOP2/Q2)

      HWUAEM=ALPHEM/(ONE-REPIGG)

      RETURN

      END