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subroutine w3w3nx(wm,w31,wp,w32,g31,g32, vertex)
c
c This subroutine computes an amplitude of the four-point coupling of
c the W-, W+ and two W3/Z/A.
c If one sets wmass=0.0, then the gggg vertex is given
c (see sect 2.9.1 of the manual).
c
c input:
c complex wm(0:3) : flow-out W- wm
c complex w31(0:3) : first W3/Z/A w31
c complex wp(0:3) : flow-out W+ wp
c complex w32(0:3) : second W3/Z/A w32
c real g31 : coupling of w31 with W-/W+
c real g32 : coupling of w32 with W-/W+
c (see the table below)
c real wmass : mass of W
c real wwidth : width of W
c
c the possible sets of the inputs are as follows:
c -------------------------------------------
c | wm | w31 | wp | w32 | g31 | g32 |
c -------------------------------------------
c | W- | W3 | W+ | W3 | gw | gw |
c | W- | W3 | W+ | Z | gw | gwwz |
c | W- | W3 | W+ | A | gw | gwwa |
c | W- | Z | W+ | Z | gwwz | gwwz |
c | W- | Z | W+ | A | gwwz | gwwa |
c | W- | A | W+ | A | gwwa | gwwa |
c -------------------------------------------
c where all the bosons are defined by the flowing-OUT quantum number.
c
c output:
c complex vertex : amplitude gamma(wm,w31,wp,w32)
c
implicit none
double complex wm(6),w31(6),wp(6),w32(6),vertex
double complex dv1(0:3),dv2(0:3),dv3(0:3),dv4(0:3),dvertx
double complex v12,v13,v14,v23,v24,v34
double precision pwm(0:3),pw31(0:3),pwp(0:3),pw32(0:3)
double precision g31,g32,gtemp
double precision rZero, rOne, rTwo
parameter( rZero = 0.0d0, rOne = 1.0d0, rTwo = 2.0d0 )
#ifdef HELAS_CHECK
double precision pm
double precision epsi
parameter( epsi = 4.0d-5 )
integer stdo
parameter( stdo = 6 )
#endif
c
c Benj's modif in order to have FR running
gtemp=rZero
if(g31.eq.rzero) gtemp=g32
if(g32.eq.rzero) gtemp=g31
c End of Benj'S modif
pwm(0) = dble( wm(5))
pwm(1) = dble( wm(6))
pwm(2) = dimag(wm(6))
pwm(3) = dimag(wm(5))
pwp(0) = dble( wp(5))
pwp(1) = dble( wp(6))
pwp(2) = dimag(wp(6))
pwp(3) = dimag(wp(5))
pw31(0) = dble( w31(5))
pw31(1) = dble( w31(6))
pw31(2) = dimag(w31(6))
pw31(3) = dimag(w31(5))
pw32(0) = dble( w32(5))
pw32(1) = dble( w32(6))
pw32(2) = dimag(w32(6))
pw32(3) = dimag(w32(5))
#ifdef HELAS_CHECK
if ( abs(wm(1))+abs(wm(2))
& +abs(wm(3))+abs(wm(4)).eq.rZero ) then
write(stdo,*) ' helas-warn : wm in w3w3xx is zero vector'
endif
if ( abs(wm(5))+abs(wm(6)).eq.rZero ) then
write(stdo,*)
& ' helas-error : wm in w3w3xx has zero momentum'
endif
if ( abs(w31(1))+abs(w31(2))
& +abs(w31(3))+abs(w31(4)).eq.rZero ) then
write(stdo,*) ' helas-warn : w31 in w3w3xx is zero vector'
endif
if ( abs(w31(5))+abs(w31(6)).eq.rZero ) then
write(stdo,*)
& ' helas-error : w31 in w3w3xx has zero momentum'
endif
if ( abs(wp(1))+abs(wp(2))
& +abs(wp(3))+abs(wp(4)).eq.rZero ) then
write(stdo,*) ' helas-warn : wp in w3w3xx is zero vector'
endif
if ( abs(wp(5))+abs(wp(5)).eq.rZero ) then
write(stdo,*)
& ' helas-error : wp in w3w3xx has zero momentum'
endif
if ( abs(w32(1))+abs(w32(2))
& +abs(w32(3))+abs(w32(4)).eq.rZero ) then
write(stdo,*) ' helas-warn : w32 in w3w3xx is zero vector'
endif
if ( abs(w32(5))+abs(w32(6)).eq.rZero ) then
write(stdo,*)
& ' helas-error : w32 in w3w3xx has zero momentum'
endif
pm = max( abs(pwm(0)),abs(pw31(0)),abs(pwp(0)),abs(pw32(0)),
& abs(pwm(1)),abs(pw31(1)),abs(pwp(1)),abs(pw32(1)),
& abs(pwm(2)),abs(pw31(2)),abs(pwp(2)),abs(pw32(2)),
& abs(pwm(3)),abs(pw31(3)),abs(pwp(3)),abs(pw32(3)) )
if ( abs(wm(5)+w31(5)+wp(5)+w32(5))
& +abs(wm(6)+w31(6)+wp(6)+w32(6)).ge.pm*epsi ) then
write(stdo,*)
& ' helas-error : wm,w31,wp,w32 in w3w3xx'
write(stdo,*)
& ' : have not balanced momenta'
endif
c Neil edited this file to allow 3-site couplings.
c if ( g31.eq.rZero ) then
c write(stdo,*) ' helas-error : g31 in w3w3xx is zero coupling'
c endif
c if ( g32.eq.rZero ) then
c write(stdo,*) ' helas-error : g32 in w3w3xx is zero coupling'
c endif
c if ( g31.lt.rZero ) then
c write(stdo,*)
c & ' helas-warn : g31 in w3w3xx is non-standard coupling'
c write(stdo,*)
c & ' : g31 = ',g31
c endif
c if ( g32.lt.rZero ) then
c write(stdo,*)
c & ' helas-warn : g32 in w3w3xx is non-standard coupling'
c write(stdo,*)
c & ' : g32 = ',g32
c endif
c End Neil's edit.
#endif
dv1(0) = dcmplx(wm(1))
dv1(1) = dcmplx(wm(2))
dv1(2) = dcmplx(wm(3))
dv1(3) = dcmplx(wm(4))
dv2(0) = dcmplx(w31(1))
dv2(1) = dcmplx(w31(2))
dv2(2) = dcmplx(w31(3))
dv2(3) = dcmplx(w31(4))
dv3(0) = dcmplx(wp(1))
dv3(1) = dcmplx(wp(2))
dv3(2) = dcmplx(wp(3))
dv3(3) = dcmplx(wp(4))
dv4(0) = dcmplx(w32(1))
dv4(1) = dcmplx(w32(2))
dv4(2) = dcmplx(w32(3))
dv4(3) = dcmplx(w32(4))
v12 = dv1(0)*dv2(0)-dv1(1)*dv2(1)-dv1(2)*dv2(2)-dv1(3)*dv2(3)
v13 = dv1(0)*dv3(0)-dv1(1)*dv3(1)-dv1(2)*dv3(2)-dv1(3)*dv3(3)
v14 = dv1(0)*dv4(0)-dv1(1)*dv4(1)-dv1(2)*dv4(2)-dv1(3)*dv4(3)
v23 = dv2(0)*dv3(0)-dv2(1)*dv3(1)-dv2(2)*dv3(2)-dv2(3)*dv3(3)
v24 = dv2(0)*dv4(0)-dv2(1)*dv4(1)-dv2(2)*dv4(2)-dv2(3)*dv4(3)
v34 = dv3(0)*dv4(0)-dv3(1)*dv4(1)-dv3(2)*dv4(2)-dv3(3)*dv4(3)
dvertx = v12*v34 + v14*v23 - rTwo*v13*v24
c Neil edited this to allow 3 site coupling.
c Now only g31 is important. g32 does nothing.
c vertex = dcmplx( dvertx ) * (g31*g32)
c vertex = dcmplx( dvertx ) * (g31)
c End Neil's edit
c
c Start of Benj's modif to have FR running
vertex = dcmplx( dvertx ) * (gtemp)
c End of Benj's modif
return
end
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