<<FeynArts`
<<FormCalc`
_Hel=0;
$FAVerbose=0;
$FCVerbose=0;

QCD 2->2 tree level parton processes

qq’->qq’

top1=CreateTopologies[0,2->2];
diags1=InsertFields[top1,{F[3,{2}],F[3,{1}]}->{F[3,{2}],F[3,{1}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{2,1},Numbering->None,SheetHeader->False];

ClearProcess[]
amp1=CalcFeynAmp[CreateFeynAmp[diags1],FermionChains->VA];
res1=(2^2/3^2 SquaredME[amp1]//.HelicityME[amp1]//.ColourME[amp1]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,T->-S-U,Alfas2->(gS^2/(4 π))^2}//Simplify)/.{S+U->T}

q(OverBar[q'])->q(OverBar[q'])

top2=CreateTopologies[0,2->2];
diags2=InsertFields[top2,{F[3,{2}],-F[3,{1}]}->{F[3,{2}],-F[3,{1}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{2,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp2=CalcFeynAmp[CreateFeynAmp[diags2],FermionChains->VA];
res2=(2^2/3^2 SquaredME[amp2]//.HelicityME[amp2]//.ColourME[amp2]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,T->-S-U,Alfas2->(gS^2/(4 π))^2}//Simplify)/.{S+U->T}

qq->qq

top3=CreateTopologies[0,2->2];
diags3=InsertFields[top3,{F[3,{2}],F[3,{2}]}->{F[3,{2}],F[3,{2}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{2,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp3=CalcFeynAmp[CreateFeynAmp[diags3],FermionChains->VA];
res3=(2^2/3^2 SquaredME[amp3]//.HelicityME[amp3]//.ColourME[amp3]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,T->-S-U,Alfas2->(gS^2/(4 π))^2}//Simplify)/.{S+U->T}

(res3+(8 (gS^4) (S^2))/(27 T U)-(4/9)(gS^4)(((S^2)+(T^2))/(U^2))-(4/9)(gS^4)(((S^2)+(U^2))/(T^2)))//Simplify[#//.U->-S-T]&

q(OverBar[q])->q’(OverBar[q'])

top4=CreateTopologies[0,2->2];
diags4=InsertFields[top4,{F[3,{2}],-F[3,{2}]}->{F[3,{1}],-F[3,{1}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{2,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp4=CalcFeynAmp[CreateFeynAmp[diags4],FermionChains->VA];
res4=(2^2/3^2 SquaredME[amp4]//.HelicityME[amp4]//.ColourME[amp4]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,T->-S-U,Alfas2->(gS^2/(4 π))^2}//Simplify)/.{S+U->T}

q(OverBar[q])->q(OverBar[q])

top5=CreateTopologies[0,2->2];
diags5=InsertFields[top5,{F[3,{2}],-F[3,{2}]}->{F[3,{2}],-F[3,{2}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{2,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp5=CalcFeynAmp[CreateFeynAmp[diags5],FermionChains->VA];
res5=(2^2/3^2 SquaredME[amp5]//.HelicityME[amp5]//.ColourME[amp5]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,T->-S-U,Alfas2->(gS^2/(4 π))^2}//Simplify)/.{S+U->T}

(res5+(8 (gS^4) (U^2))/(27 S T)-(4/9)(gS^4)(((S^2)+(U^2))/(T^2))-(4/9)(gS^4)(((T^2)+(U^2))/(S^2)))//Simplify[#//.U->-S-T]&

q(OverBar[q])->gg

top6=CreateTopologies[0,2->2];
diags6=InsertFields[top6,{F[3,{2}],-F[3,{2}]}->{V[5],V[5]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{3,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp6=CalcFeynAmp[CreateFeynAmp[diags6],FermionChains->VA];
res6=(1/(3^2))SquaredME[amp6]//.HelicityME[amp6]//.ColourME[amp6]//.Subexpr[];
res61= PolarizationSum[res6,GaugeTerms->False]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,Alfas2->((((gS^2)/(4π)))^2)}//Simplify[#]&//Expand

(res61-((32 (gS^4) )/27 )(((T^2)+(U^2))/(T U))+(8/3)(gS^4)(((T^2)+(U^2))/(S^2)))//Simplify[#//.U->-S-T]&

gg->q(OverBar[q])

top7=CreateTopologies[0,2->2];
diags7=InsertFields[top7,{V[5],V[5]}->{F[3,{2}],-F[3,{2}]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{3,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp7=CalcFeynAmp[CreateFeynAmp[diags7],FermionChains->VA];
res7=((2^2)/((2^2)(8^2)))SquaredME[amp7]//.HelicityME[amp7]//.ColourME[amp7]//.Subexpr[];
res71= PolarizationSum[res7,GaugeTerms->False]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,Alfas2->((((gS^2)/(4π)))^2)}//Simplify[#]&//Expand

(res71-((1 (gS^4) )/6 )(((T^2)+(U^2))/(T U))+(3/8)(gS^4)(((T^2)+(U^2))/(S^2)))//Simplify[#//.U->-S-T]&

gq->gq

top8=CreateTopologies[0,2->2];
diags8=InsertFields[top8,{F[3,{2}],V[5]}->{F[3,{2}],V[5]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{3,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp8=CalcFeynAmp[CreateFeynAmp[diags8],FermionChains->VA];
res8=(2/(2*3*8))SquaredME[amp8]//.HelicityME[amp8]//.ColourME[amp8]//.Subexpr[];
res81= PolarizationSum[res8,GaugeTerms->False]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,Alfas2->((((gS^2)/(4π)))^2)}//Simplify[#]&//Expand

(res81+((4 (gS^4) )/9 )(((S^2)+(U^2))/(S U))-(gS^4)(((S^2)+(U^2))/(T^2)))//Simplify[#//.U->-S-T]&

gg->gg

top9=CreateTopologies[0,2->2];
diags9=InsertFields[top9,{V[5],V[5]}->{V[5],V[5]},InsertionLevel->{Classes},Model->"SMQCD",ExcludeParticles->{S[1],S[2],V[1],V[2]}];
Paint[%,ColumnsXRows->{4,1},Numbering->None,SheetHeader->False];

ClearProcess[];
amp9=CalcFeynAmp[CreateFeynAmp[diags9],FermionChains->VA];
res9=(1/((2^2)*(8^2)))SquaredME[amp9]//.ColourME[amp9]//.Subexpr[];
res91= PolarizationSum[res9,GaugeTerms->False]//.Subexpr[]//.{Den[p2_,m2_]:>1/(p2-m2),MU2->0,MC2->0,MC->0,MU->0,Alfas2->((((gS^2)/(4π)))^2)}//Simplify[#]&//Expand

(res91-((9 (gS^4) )/2 )(3-(T U)/(S^2)-(S U)/(T^2)-(S T)/(U^2)))//Simplify[#//.U->-S-T]&