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I am learning Mathematica and FeynCalc by doing some basic cross section calculations.

I have an issue with trace calculations: When I plug in for instance the interference term for ee->tautau, the result comes out with the g00 component of the metric tensor explicitly written, i.e. not set to 1 as it should be. This means I have to manually remove it before the next step in the calculation.

I have tried doing something like MetricTensor[0,0]:=1, but it did not help. I am probably missing some syntax, but can you point me to the correct way of doing it?

Here is my code:

  Contract[e^2*gz^2/4/(s*(s - Mz^2 + Mz*Gammaz))/4*
    Tr[GA[mu].(GS[q2] - M).GA[0].(cV - cA GA[5]).GA[0].GA[
       nu].(GS[q1] + M)]*
    Tr[GA[mu].(GS[p1] + m).GA[0].(cV - cA GA[5]).GA[0].GA[
       nu].(GS[p2] - m)]]];
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