Comment 3 for bug 1519852

Dear Nikolai,

I'm back on this after the season of application.
I'm actually not sure that the sign is wrong in madevent.
I have check all those signs and they are all correct,
The minus sign in the matrix came from the epsilon_ijk color structure
while the minus sign in the JAMP definition cames from the permutation of two fermions.

On the other hand, I have found a bug in MadWith (it was only using one Feynman Diagram and was not considering the symmetric one). The fact that it was returning the correct value was just pure coincidence.

I have also looked at the paper and if I'm correct:
1) in Equation 17. We can drop the first line since this correspond to some mixing which are not present in your model.
2) They have the same epsilon factor (\epsilon^{\alpha\beta\gamma})for all the line.
Personally, I would have expect to have the following factor
\epsilon^{\beta\gamma\alpha}
\epsilon^(\alpha\gamma\beta)
\epsilon^(\alpha\beta\gamma)
for each line.

I therefore think that the problem is in MadWith and in the analytical paper rather than in the "standard" event generation.

Do you agree with me?

Cheers,

Olivier