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hvvxxu.F
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subroutine hvvxxu(v1,v2,gc,smass,swidth , hvv)
c
c This subroutine computes an off-shell scalar current from the vector-
c vector-scalar coupling.
c
c input:
c complex v1(6) : first vector v1
c complex v2(6) : second vector v2
c complex gc : coupling constant gvvh
c real smass : mass of OUTPUT scalar s
c real swidth : width of OUTPUT scalar s
c
c output:
c complex hvv(3) : off-shell scalar current j(s:v1,v2)
c
implicit none
double complex v1(6),v2(6),gc,hvv(3),dg
double precision q(0:3),smass,swidth,q2
double precision rZero
parameter( rZero = 0.0d0 )
#ifdef HELAS_CHECK
double complex cZero
parameter( cZero = ( 0.0d0, 0.0d0 ) )
integer stdo
parameter( stdo = 6 )
#endif
c
#ifdef HELAS_CHECK
if ( abs(v1(1))+abs(v1(2))+abs(v1(3))+abs(v1(4)).eq.rZero) then
write(stdo,*) ' helas-warn : v1 in hvvxxx is zero vector'
endif
if ( abs(v1(5))+abs(v1(6)).eq.rZero ) then
write(stdo,*)
& ' helas-error : v1 in hvvxxx has zero momentum'
endif
if ( abs(v2(1))+abs(v2(2))+abs(v2(3))+abs(v2(4)).eq.rZero ) then
write(stdo,*) ' helas-warn : v2 in hvvxxx is zero vector'
endif
if ( abs(v2(5))+abs(v2(6)).eq.rZero ) then
write(stdo,*)
& ' helas-error : v2 in hvvxxx has zero momentum'
endif
if ( gc.eq.cZero ) then
write(stdo,*) ' helas-error : gc in hvvxxx is zero coupling'
endif
if ( smass.lt.rZero ) then
write(stdo,*) ' helas-error : smass in hvvxxx is negative'
write(stdo,*) ' : smass = ',smass
endif
if ( swidth.lt.rZero ) then
write(stdo,*) ' helas-error : swidth in hvvxxx is negative'
write(stdo,*) ' : swidth = ',swidth
endif
#endif
hvv(2) = v1(5)+v2(5)
hvv(3) = v1(6)+v2(6)
q(0) = dble( hvv(2))
q(1) = dble( hvv(3))
q(2) = dimag(hvv(3))
q(3) = dimag(hvv(2))
q2 = q(0)**2-(q(1)**2+q(2)**2+q(3)**2)
#ifdef HELAS_CHECK
if ( abs(hvv(2))+abs(hvv(3)).eq.rZero ) then
write(stdo,*)
& ' helas-error : hvv in hvvxxx has zero momentum'
endif
if ( swidth.eq.rZero .and. q2.eq.smass**2 ) then
write(stdo,*)
& ' helas-error : hvv in hvvxxx is on smass pole'
write(stdo,*)
& ' : q = ',q(0),q(1),q(2),q(3)
write(stdo,*)
& ' : abs(q)= ',sqrt(abs(q2))
hvv(1) = cZero
return
endif
#endif
dg = -gc*dcmplx( 1.0d0, swidth/smass )
& /dcmplx( q2-smass**2, swidth*q2/smass )
hvv(1) = dg*(v1(1)*v2(1)-v1(2)*v2(2)-v1(3)*v2(3)-v1(4)*v2(4))
c
return
end

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