Name: andrea (email_not_shown)
Date: 02/06/08-12:59:05 PM Z

with FeynCalc 4.1 and Mathematica 5.1 (and previous versions)

these lines

M00:=Spinor[p1,m1].GA[a].GA[7].Spinor[p2,m2] \
Spinor[k1,M1].GA[b].GA[7].Spinor[k2]
cM00:=ComplexConjugate[M00]
FermionSpinSum[M00 cM00]/.DiracTrace->TR

gave

16*Pair[Momentum[k1], Momentum[p1]]*Pair[Momentum[k2], Momentum[p2]]

that is correct since the two currents are treated in a different way
when traces are taken and then they are contracted.
now with Mathematica and FeynCalc 6

i get

16*Pair[Momentum[k1], Momentum[k2]]*Pair[Momentum[p1], Momentum[p2]].

how can i get he old result without changing everything?

so far i succeeded with

M00:=MT[a,b]Spinor[p1,m1].GA[a].GA[7].Spinor[p2,m2] \
Spinor[k1,M1].GA[b].GA[7].Spinor[k2]
cM00:=ComplexConjugate[M00]/.{a->ComplexIndex[a],b->ComplexIndex[b]}
Simplify[Contract[FermionSpinSum[M00 cM00]/.DiracTrace->TR]]

but this would make me change most of the rest of the code.

thanks a lot,

a

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