1
subroutine sssxxx(s1,s2,s3,gc , vertex)
3
c This subroutine computes an amplitude of the three-scalar coupling.
6
c complex s1(3) : first scalar s1
7
c complex s2(3) : second scalar s2
8
c complex s3(3) : third scalar s3
9
c complex gc : coupling constant ghhh
12
c complex vertex : amplitude gamma(s1,s2,s3)
15
double complex s1(3),s2(3),s3(3),gc,vertex
18
double precision p0,p1,p2,p3,q0,q1,q2,q3,r0,r1,r2,r3,pm
20
parameter( epsi = 4.0d-5 )
21
double precision rZero
22
parameter( rZero = 0.0d0 )
24
parameter( cZero = ( 0.0d0, 0.0d0 ) )
42
if ( s1(1).eq.cZero ) then
43
write(stdo,*) ' helas-warn : s1 in sssxxx is zero scalar'
45
if ( abs(s1(2))+abs(s1(3)).eq.rZero ) then
47
& ' helas-error : s1 in sssxxx has zero momentum'
49
if ( s2(1).eq.cZero ) then
50
write(stdo,*) ' helas-warn : s2 in sssxxx is zero scalar'
52
if ( abs(s2(2))+abs(s2(3)).eq.rZero ) then
54
& ' helas-error : s2 in sssxxx has zero momentum'
56
if ( s3(1).eq.cZero ) then
57
write(stdo,*) ' helas-warn : s3 in sssxxx is zero scalar'
59
if ( abs(s3(2))+abs(s3(3)).eq.rZero ) then
61
& ' helas-error : s3 in sssxxx has zero momentum'
63
pm = max( abs(p0),abs(q0),abs(r0),abs(p1),abs(q1),abs(r1),
64
& abs(p2),abs(q2),abs(r2),abs(p3),abs(q3),abs(r3) )
65
if ( abs(s1(2)+s2(2)+s3(2))+abs(s1(3)+s2(3)+s3(3))
68
& ' helas-error : s1,s2,s3 in sssxxx'
70
& ' : have not balanced momenta'
72
if ( gc.eq.cZero ) then
74
& ' helas-error : gc in sssxxx is zero coupling'
78
vertex = gc*s1(1)*s2(1)*s3(1)