Four-fermion Operator
Dear MadGraph team,
I'm interested in implementing a four-fermion operator through the FeynRules-MadGraph chain. By reading through old questions posted here, I understood that there is some issue regarding the four-fermion operator. I am wondering whether this issue has been resolved or not in the current versions of FeynRules (> 2.3) and MadGraph (> MG5_aMC_v2_3_3).
1. In particular, I'm trying to implement a simple four-fermion operator:
Lag := 2 Pi Eta /(cutoff^2) (ubar.Ga[
FeynRules successfully generates UFO file, with some suspicious warning:
``Warning: Multi-Fermion operators are not yet fully supported!``
Nevertheless, this UFO can successfully generate events for the following process:
generate u u > u u NP^2==2
The resulting cross section matches to a manual calculation. So the thing seems to be working well.
2. I'm further wondering whether MadGraph can deal with a full QCD + NP process as well (i.e. |QCD + NP|^2):
generate p p > j j NP <= 1
where NP is an interaction vertex of the four-fermion operator. I am especially wondering whether signs of interference terms are correctly taken care of by MadGraph.
Thank you in advance!
Best regards
Jeong-han Kim
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- Solved by:
- Olivier Mattelaer
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