Coding rule violations corrected.

[u/mrichter/AliRoot.git] / HERWIG / src / hwucff.f

CDECK  ID>, HWUCFF.

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

*-- Author :    Bryan Webber and Ian Knowles

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

      SUBROUTINE HWUCFF(I,J,QSQ,CLF)

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

C     Calculates basic coefficients in cross-section formula for

C     ffbar --> f'fbar', at virtuality QSQ, I labels initial, J

C     labels final fermion; type given as:

C        I,J= 1- 6: d,u,s,c,b,t

C           =11-16: e,nu_e,mu,nu_mu,tau,nu_tau

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

      INCLUDE 'HERWIG61.INC'

      DOUBLE PRECISION QSQ,CLF(7),POL1,POL2,QIF,VI,AI,VF,AF,PG,DQM,PMW,

     & DEN,XRE,XIM,XSQ,VI2,AI2,VF2,AF2,PG2,PG12,DQM2,PMW2,DEN2,XRE2,

     & XIM2,XSQ2,XRE12,XIM12

      INTEGER I,J

C Longitudinal Polarisation factors

      POL1=1.-EPOLN(3)*PPOLN(3)

      POL2=PPOLN(3)-EPOLN(3)

C Standard model couplings

      QIF=QFCH(I)*QFCH(J)

      VI=VFCH(I,1)

      AI=AFCH(I,1)

      VF=VFCH(J,1)

      AF=AFCH(J,1)

      PG=POL1*(VI**2+AI**2)+POL2*2.*VI*AI

C Z propagator factors

      DQM=QSQ-RMASS(200)**2

      PMW=GAMZ*RMASS(200)

      DEN=QSQ/(DQM**2+PMW**2)

      XRE=DEN*DQM

      XIM=DEN*PMW

      XSQ=DEN*QSQ

C Calculate cross-section coefficients

      CLF(1)=POL1*QIF**2+XRE*2.*QIF*(POL1*VI+POL2*AI)*VF

     &      +XSQ*PG*(VF**2+AF**2)

      CLF(2)=CLF(1)-2.*XSQ*PG*AF**2

      CLF(3)=2.*(XRE*QIF*(POL1*AI+POL2*VI)*AF

     &      +XSQ*(POL1*2.*VI*AI+POL2*(VI**2+AI**2))*VF*AF)

      IF (TPOL) THEN

         CLF(4)=QIF**2+XRE*2.*QIF*VI*VF+XSQ*(VI**2-AI**2)*(VF**2+AF**2)

         CLF(5)=CLF(4)-2.*XSQ*(VI**2-AI**2)*AF**2

         CLF(6)=XIM*2.*QIF*AI*VF

         CLF(7)=CLF(6)

      ENDIF

      IF (ZPRIME) THEN

C Z' couplings:

         VI2=VFCH(I,2)

         AI2=AFCH(I,2)

         VF2=VFCH(J,2)

         AF2=AFCH(J,2)

         PG2=POL1*(VI2**2+AI2**2)+POL2*2.*VI2*AI2

         PG12=POL1*(VI*VI2+AI*AI2)+POL2*(VI*AI2+AI+VI2)

C Z' propagator factors

         DQM2=QSQ-RMASS(202)**2

         PMW2=RMASS(202)*GAMZP

         DEN2=QSQ/(DQM2**2+PMW2**2)

         XRE2=DEN2*DQM2

         XIM2=DEN2*PMW2

         XSQ2=DEN2*QSQ

         XRE12=DEN*DEN2*(DQM*DQM2+PMW*PMW2)

         XIM12=DEN*DEN2*(DQM*PMW2-DQM2*PMW)

C Additional contributions to cross-section coefficients

         CLF(1)=CLF(1)+XRE2*2.*QIF*(POL1*VI2+POL2*AI2)*VF2

     &    +XSQ2*PG2*(VF2**2+AF2**2)+XRE12*2.*PG12*(VF*VF2+AF*AF2)

         CLF(2)=CLF(1)-2.*(XSQ2*PG2*AF2**2+XRE12*2.*PG12*AF*AF2)

         CLF(3)=CLF(3)+2.*(XRE2*QIF*(POL1*AI2+POL2*VI2)*AF2

     &    +XSQ2*(POL1*2.*VI2*AI2+POL2*(VI2**2+AI2**2))*VF2*AF2

     &    +XRE12*(POL1*(VI*AI2+AI*VI2)+POL1*(VI*VI2+AI*AI2))

     &    *(VF*VF2+AF*AF2))

         IF (TPOL) THEN

            CLF(4)=CLF(4)+XRE2*2.*QIF*VI2*VF2

     &       +XSQ2*(VI2**2-AI2**2)*(VF2**2+AF2**2)

     &       +XRE12*2.*(VI*VI2-AI*AI2)*(VF*VF2+AF*AF2)

            CLF(5)=CLF(4)-2*(XSQ2*(VI2**2-AI2**2)*AF2**2

     &       +XRE12*2.*(VI*VI2-AI*AI2)*AF*AF2)

            CLF(6)=CLF(6)+2.*(XIM2*QIF*AI2*VF2

     &       -XIM12*(VI*AI2-AI*VI2)*(VF*VF2+AF*AF2))

            CLF(7)=CLF(6)+4.*XIM12*(VI*AI2-AI*AI2)*AF*AF2

         ENDIF

      ENDIF

      RETURN

      END