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50.9.3
by Johan Alwall
Added Template and HELAS into bzr |
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subroutine vssxxx(vc,s1,s2,gc , vertex) |
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c
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c This subroutine computes an amplitude from the vector-scalar-scalar
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c coupling. The coupling is absent in the minimal SM in unitary gauge.
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c
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c complex vc(6) : input vector v
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c complex s1(3) : first scalar s1
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c complex s2(3) : second scalar s2
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c complex gc : coupling constant (s1 charge)
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c
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c examples of the coupling constant gc for SUSY particles are as follows:
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c -----------------------------------------------------------
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c | s1 | (q,i3) of s1 || v=a | v=z | v=w |
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c -----------------------------------------------------------
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c | nu~_l | ( 0 , +1/2) || --- | gzn(1) | gwf(1) |
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c | e~_l | ( -1 , -1/2) || gal(1) | gzl(1) | gwf(1) |
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c | u~_l | (+2/3 , +1/2) || gau(1) | gzu(1) | gwf(1) |
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c | d~_l | (-1/3 , -1/2) || gad(1) | gzd(1) | gwf(1) |
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c -----------------------------------------------------------
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c | e~_r-bar | ( +1 , 0 ) || -gal(2) | -gzl(2) | -gwf(2) |
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c | u~_r-bar | (-2/3 , 0 ) || -gau(2) | -gzu(2) | -gwf(2) |
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c | d~_r-bar | (+1/3 , 0 ) || -gad(2) | -gzd(2) | -gwf(2) |
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c -----------------------------------------------------------
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c where the s1 charge is defined by the flowing-OUT quantum number.
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c
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c output:
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c complex vertex : amplitude gamma(v,s1,s2)
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c
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implicit none |
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double complex vc(6),s1(3),s2(3),gc,vertex |
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double precision p(0:3) |
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#ifdef HELAS_CHECK
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double precision p0,p1,p2,p3,q0,q1,q2,q3,r0,r1,r2,r3,pm |
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double precision epsi |
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parameter( epsi = 4.0d-5 ) |
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double precision rZero |
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parameter( rZero = 0.0d0 ) |
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double complex cZero |
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parameter( cZero = ( 0.0d0, 0.0d0 ) ) |
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integer stdo |
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parameter( stdo = 6 ) |
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#endif
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c
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#ifdef HELAS_CHECK
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p0 = dble( s1(2)) |
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p1 = dble( s1(3)) |
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p2 = dimag(s1(3)) |
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p3 = dimag(s1(2)) |
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q0 = dble( s2(2)) |
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q1 = dble( s2(3)) |
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q2 = dimag(s2(3)) |
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q3 = dimag(s2(2)) |
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r0 = dble( vc(5)) |
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r1 = dble( vc(6)) |
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r2 = dimag(vc(6)) |
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r3 = dimag(vc(5)) |
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if ( abs(vc(1))+abs(vc(2))+abs(vc(3))+abs(vc(4)).eq.rZero ) then |
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write(stdo,*) ' helas-warn : vc in vssxxx is zero vector' |
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endif |
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if ( abs(vc(5))+abs(vc(6)).eq.rZero ) then |
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write(stdo,*) |
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& ' helas-error : vc in vssxxx has zero momentum' |
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endif |
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if ( s1(1).eq.cZero ) then |
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write(stdo,*) ' helas-warn : s1 in vssxxx is zero scalar' |
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endif |
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if ( abs(s1(2))+abs(s1(3)).eq.rZero ) then |
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write(stdo,*) |
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& ' helas-error : s1 in vssxxx has zero momentum' |
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endif |
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if ( s2(1).eq.cZero ) then |
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write(stdo,*) ' helas-warn : s2 in vssxxx is zero scalar' |
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endif |
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if ( abs(s2(2))+abs(s2(3)).eq.rZero ) then |
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write(stdo,*) |
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& ' helas-error : s2 in vssxxx has zero momentum' |
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endif |
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pm = max( abs(p0),abs(q0),abs(r0),abs(p1),abs(q1),abs(r1), |
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& abs(p2),abs(q2),abs(r2),abs(p3),abs(q3),abs(r3) ) |
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if ( abs(vc(5)+s1(2)+s2(2))+abs(vc(6)+s1(3)+s2(3)) |
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& .ge.pm*epsi ) then |
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write(stdo,*) |
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& ' helas-error : vc,s1,s2 in vssxxx' |
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write(stdo,*) |
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& ' : have not balanced momenta' |
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endif |
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if ( gc.eq.cZero ) then |
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write(stdo,*) ' helas-error : g in vssxxx is zero coupling' |
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endif |
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#endif
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p(0) = dble( s1(2)-s2(2)) |
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p(1) = dble( s1(3)-s2(3)) |
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p(2) = dimag(s1(3)-s2(3)) |
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p(3) = dimag(s1(2)-s2(2)) |
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vertex = gc*s1(1)*s2(1) |
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& *(vc(1)*p(0)-vc(2)*p(1)-vc(3)*p(2)-vc(4)*p(3)) |
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c
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return |
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end |