Hi,
could you please specify the result that you expect or get by hand?
Cheers,
Vladyslav
Am 14.04.2015 um 14:20 schrieb Rakhi:
> Hi, I'm computing a spin sum and propagator contraction with FeynCalc 8.2.0 and the results of the contraction don't agree with what I expect (also disagrees with computation by hand).
>
> Code to get spin sum
> ====================================
> ClearScalarProducts
> ScalarProduct[q, q] = M^2; ScalarProduct[k1, k1] = m1^2;
> ScalarProduct[k2, k2] = m2^2; ScalarProduct[k3, k3] = m3^2;
> ScalarProduct[k2, k3] = 1/2 (M^2 + m1^2 - m2^2 - m3^2 - 2 ScalarProduct[q, k1]);
> ScalarProduct[k1, k3] = 1/2 (M^2 - m1^2 + m2^2 - m3^2 - 2 ScalarProduct[q, k2]);
> ScalarProduct[k1, k2] = 1/2 (M^2 - m1^2 - m2^2 + m3^2 - 2 ScalarProduct[q, k3]);
> ScalarProduct[k3, q] = M^2 - ScalarProduct[q, k2] - ScalarProduct[k1, q];
>
> m2 := 0;
>
> s1 = Spinor[q, M].GA[\[Mu]].(-Ni2 GA[7] + Ni3 GA[6]).Spinor[k1, m1];
> s1C = ComplexConjugate[s1] /. {\[Mu] -> \[Rho], Ni3 -> Conjugate[Ni3], Ni2 -> Conjugate[Ni2]};
> s2 = Spinor[k2, m2].GA[\[Nu]].GA[7].Spinor[-k3, m3];
> s2C = ComplexConjugate[s2] /. {\[Nu] -> \[Sigma]};
> Mint = FermionSpinSum[s1 s1C] FermionSpinSum[s2 s2C] /. DiracTrace -> Tr
> ============================
>
> Then I contract with a massive W propagator:
>
> =============================
> prop[\[Mu]_, \[Nu]_, p_, m_] := (MT[\[Mu], \[Nu]] - (FV[p, \[Mu]] FV[p, \[Nu]])/m^2);
> Ampsq = Contract[prop[\[Rho], \[Sigma], q - k1, mw].Mint.prop[\[Mu], \[Nu], q - k1, mw]];
> =============================
>
> Am I not using the commands correctly, or is there some sort of bug?
>
> Many thanks in advance for your help,
> Rakhi
>
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