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.
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: {\alpha\ beta\gamma} )for all the line. {\beta\ gamma\alpha} (\alpha\ gamma\beta) (\alpha\ beta\gamma)
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^
Personally, I would have expect to have the following factor
\epsilon^
\epsilon^
\epsilon^
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