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subroutine ggggtx(va,vb,vc,vd,tc,gc,gt , vertex)
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c This subroutine computes the portion of the amplitude of the five-point
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c coupling of a tensor boson with 4 massless color octet gauge bosons
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c (gluons) corresponding to the color structure f^{a,b,e} f{c,d,e}.
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c To obtain the complete amplitude, this coupling must be called three
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c times (once for each color structure) with the following permutations:
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c call ggggtx(va,vb,vc,vd,tc,gc,gt , vertex1)
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c call ggggtx(va,vc,vd,vb,tc,gc,gt , vertex2)
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c call ggggtx(va,vd,vb,vc,tc,gc,gt , vertex3)
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c complex va(6) : boson with adjoint color index a va
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c complex vb(6) : boson with adjoint color index b vb
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c complex vc(6) : boson with adjoint color index c vc
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c complex vd(6) : boson with adjoint color index d vd
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c complex tc(18) : input tensor T
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c real gc : coupling constant gs
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c complex gt : coupling constant gtv=-1/Lambda
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c complex vertex : amplitude gamma(va,vb,vc,vd,T)
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c- by Q.Li - OCT. 2006
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double complex va(6), vb(6), vc(6), vd(6), tc(18), gt, vertex
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double complex vab,vac,vad,vbc,vbd,vcd,ft(6,4),dvertx
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double complex T00, T12, T13, T14, T23, T24, T34
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double complex TV24,TV23,TV14,TV13
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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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T00 = ft(1,1)-ft(2,2)-ft(3,3)-ft(4,4)
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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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TV14 = rtwo*(ft(1,1)*va(1)*vd(1)+ft(2,2)*va(2)*vd(2)
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&+ft(3,3)*va(3)*vd(3)+ft(4,4)*va(4)*vd(4))
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TV13 = rtwo*(ft(1,1)*va(1)*vc(1)+ft(2,2)*va(2)*vc(2)
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&+ft(3,3)*va(3)*vc(3)+ft(4,4)*va(4)*vc(4))
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TV24 = rtwo*(ft(1,1)*vb(1)*vd(1)+ft(2,2)*vb(2)*vd(2)
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&+ft(3,3)*vb(3)*vd(3)+ft(4,4)*vb(4)*vd(4))
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TV23 = rtwo*(ft(1,1)*vb(1)*vc(1)+ft(2,2)*vb(2)*vc(2)
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&+ft(3,3)*vb(3)*vc(3)+ft(4,4)*vb(4)*vc(4))
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TV14 = TV14- T12*(va(1)*vd(2) + va(2)*vd(1))
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& - T13*(va(1)*vd(3) + va(3)*vd(1))
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& - T14*(va(1)*vd(4) + va(4)*vd(1))
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& + T23*(va(2)*vd(3) + va(3)*vd(2))
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& + T24*(va(2)*vd(4) + va(4)*vd(2))
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& + T34*(va(3)*vd(4) + va(4)*vd(3))
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TV13 = TV13 - T12*(va(1)*vc(2) + va(2)*vc(1))
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& - T13*(va(1)*vc(3) + va(3)*vc(1))
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& - T14*(va(1)*vc(4) + va(4)*vc(1))
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& + T23*(va(2)*vc(3) + va(3)*vc(2))
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& + T24*(va(2)*vc(4) + va(4)*vc(2))
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& + T34*(va(3)*vc(4) + va(4)*vc(3))
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TV24 = TV24 - T12*(vb(1)*vd(2) + vb(2)*vd(1))
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& - T13*(vb(1)*vd(3) + vb(3)*vd(1))
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& - T14*(vb(1)*vd(4) + vb(4)*vd(1))
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& + T23*(vb(2)*vd(3) + vb(3)*vd(2))
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& + T24*(vb(2)*vd(4) + vb(4)*vd(2))
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& + T34*(vb(3)*vd(4) + vb(4)*vd(3))
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TV23 = TV23 - T12*(vb(1)*vc(2) + vb(2)*vc(1))
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& - T13*(vb(1)*vc(3) + vb(3)*vc(1))
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& - T14*(vb(1)*vc(4) + vb(4)*vc(1))
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& + T23*(vb(2)*vc(3) + vb(3)*vc(2))
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& + T24*(vb(2)*vc(4) + vb(4)*vc(2))
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& + T34*(vb(3)*vc(4) + vb(4)*vc(3))
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vab = va(1)*vb(1)-va(2)*vb(2)-va(3)*vb(3)-va(4)*vb(4)
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vac = va(1)*vc(1)-va(2)*vc(2)-va(3)*vc(3)-va(4)*vc(4)
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vad = va(1)*vd(1)-va(2)*vd(2)-va(3)*vd(3)-va(4)*vd(4)
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vbc = vb(1)*vc(1)-vb(2)*vc(2)-vb(3)*vc(3)-vb(4)*vc(4)
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vbd = vb(1)*vd(1)-vb(2)*vd(2)-vb(3)*vd(3)-vb(4)*vd(4)
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vcd = vc(1)*vd(1)-vc(2)*vd(2)-vc(3)*vd(3)-vc(4)*vd(4)
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dvertx = -TV13*vbd-TV24*vac+TV23*vad+TV14*vbc
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&+vbd*vac*T00-vad*vbc*T00
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vertex = -dvertx * gc*gc*gt