Exercise 1

Two-jet cross sections (Only QCD; mass ignored) : Ellis-Stirling-Webber Sec.7.5

Work Space

Exit[];

Set Up

$Language="English";
<<FeynArts`
<<FormCalc`

Topology

topologies=CreateTopologies[0,XXXXXXXXXXXXXXXXXXX];

Diagram

diagrams=InsertFields[topologies,
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX,
InsertionLevel->{Classes},
Model->"SMQCD",
ExcludeParticles->{XXXXXXXXXXXXXXXXXXXXXXX}];

Paint[diagrams];

Amplitude

ClearProcess[];
amplitude=CalcFeynAmp[CreateFeynAmp[diagrams],FermionChains->VA];
squared=SquaredME[amplitude];

HelicityME

_Hel=0;

ColourME

PolarizationSum

Ignoring mass etc...

%//.Join[Abbr[],Subexpr[],{Den[p2_,m2_]:>(1/(p2-m2)),MU->0,MU2->0,Alfas2->(((((gs^2)/(4π))))^2)}]

LESSON

×2 for each FINAL fermion

DIVIDE by INITIAL colour factor

DIVIDE by INITIAL vector particles.