subroutine qqb_tbb_z(p,z)
      implicit none
      include 'constants.f'
      include 'masses.f'
      include 'qcdcouple.f'
      include 'scale.f'
      include 'PR_new.f'
      include 'agq.f'
      integer is
      double precision z,xl12,p(mxpart,4),dot,ii_qq,ii_qg,tempqq,tempqg,
     . mbar12,ff_1mqq

      xl12=dlog(two*dot(p,1,2)/musq)
      mbar12=mt/dsqrt(two*dot(p,1,2))

c----contributions for one leg
      do is=1,3
      tempqq=+ason2pi*cf*(ii_qq(z,xl12,is)+ff_1mqq(z,xl12,mbar12,is))
      tempqg=+ason2pi*tr*ii_qg(z,xl12,is)

      Q1(q,q,a,is)=tempqq
      Q2(a,a,q,is)=tempqq
      Q1(a,a,q,is)=tempqq
      Q2(q,q,a,is)=tempqq

      Q2(a,g,q,is)=tempqg
      Q2(q,g,a,is)=tempqg
      Q1(a,g,q,is)=tempqg
      Q1(q,g,a,is)=tempqg
      enddo

      return
      end