text: c--- File written by FORM program adecayW_v.frm on Thu Mar  1 12:30:14 CST 2012
        subroutine adecayW_v(p,pqq,pqb,pc,m)
        implicit none
  ************************************************************************
  *     Author: R.K. Ellis, January 2012                                 *
  *     Virtual corrections to                                           *
  *     antitop decay  a --> qq(pqq)+qb(pqb)+bbar(pc)                    *
  *     with bottom and top masses (and no radiation)                    *
  *     in massless spinor notation                                      *
  *     pqq,pqb,pc are integers that point to                            *
  *     the appropriate four-momenta in p                                *
  *     pqq=electron                                                     *
  *     pqb=antineutrino                                                 *
  *     pc=anti-bottom quark                                             *
  *     q(c) is rendered massless wrt to pqb                             *
  *     q(a) is rendered massless wrt to pqq                             *
  *     returned m(apol,cpol)                                            *
  ************************************************************************
        include 'constants.f'
        include 'zprods_decl.f'
        include 'sprods_com.f'
        include 'masses.f'
        double precision p(mxpart,4),q(mxpart,4),dot,sw,ala,alc,c0,ct
        double complex m(2,2),cprop,c0L
        integer qb,a,c,qq,si,pc,pqq,pqb
        parameter(a=1,qq=3,qb=4,c=2)
        do si=1,4
        q(a,si)=p(pqq,si)+p(pqb,si)+p(pc,si)
        q(qq,si)=p(pqq,si)
        q(qb,si)=p(pqb,si)
        q(c,si)=p(pc,si)
        enddo
        ala=mt**2/(2d0*dot(q,a,qq))
        alc=mb**2/(2d0*dot(q,c,qb))
        do si=1,4
        q(a,si)=q(a,si)-ala*q(qq,si)
        q(c,si)=q(c,si)-alc*q(qb,si)
        enddo
        call spinoru(4,q,za,zb)
        sw=s(qq,qb)
        call coefswdk(sw,ct,c0)
        c0L=dcmplx(c0+ct)
        cprop=dcmplx(sw-wmass**2,wmass*wwidth)
  C---order of polarizations is m(apol,cpol)
        m(1,1)= czip
  
        m(1,2)= czip
  
        m(2,1)= czip
  
        m(2,2)= + cprop**(-1) * ( za(qq,a)*zb(qb,c)*c0L )
  
        return
        end
  