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subroutine sstxxx(s1,s2,tc,gt,smass , vertex)
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c This subroutine computes an amplitude of the three-point coupling of
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c two scalar and a tensor boson.
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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 tc(18) : input tensor T
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c complex gt : coupling constant gts=-1/Lambda
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c real smass : scalar mass m_s
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c complex vertex : amplitude gamma(s1,s2,T)
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c- by Q.Li - OCT. 2006
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double complex s1(3), s2(3), tc(18), vertex
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double precision smass
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double complex ft(6,4)
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double complex T12, T13, T14, T23, T24, T34
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double precision ps1(4), ps2(4)
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double precision rZero, rTwo
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parameter( rZero = 0.0d0, rTwo = 2.0d0 )
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parameter( cZero = ( 0.0d0, 0.0d0 ) )
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ps2(1) = -dreal(s2(2))
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ps2(2) = -dreal(s2(3))
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ps2(3) = -dimag(s2(3))
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ps2(4) = -dimag(s2(2))
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T12 = ft(1,2) + ft(2,1)
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T13 = ft(1,3) + ft(3,1)
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T14 = ft(1,4) + ft(4,1)
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T23 = ft(2,3) + ft(3,2)
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T24 = ft(2,4) + ft(4,2)
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T34 = ft(3,4) + ft(4,3)
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TKK=TKK+ft(i,i)*ps1(i)*ps2(i)
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TKK = TKK - T12*(ps1(1)*ps2(2) + ps1(2)*ps2(1))
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& - T13*(ps1(1)*ps2(3) + ps1(3)*ps2(1))
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& - T14*(ps1(1)*ps2(4) + ps1(4)*ps2(1))
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& + T23*(ps1(2)*ps2(3) + ps1(3)*ps2(2))
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& + T24*(ps1(2)*ps2(4) + ps1(4)*ps2(2))
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& + T34*(ps1(3)*ps2(4) + ps1(4)*ps2(3))
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vertex = TKK+(ft(1,1)-ft(2,2)-ft(3,3)-ft(4,4))
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& *(smass**2-ps1(1)*ps2(1)+ps1(2)*ps2(2)
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& +ps1(3)*ps2(3)+ps1(4)*ps2(4))
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vertex = vertex * gt*s1(1)*s2(1)