Comment 3 for bug 921487
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| Johan Alwall (johan-alwall) wrote Re: cross-section highly dependent on convention for PDG particle code | #3 |
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bbfa235
(Get the code!)
Hello Ben,
Many thanks for your report. We wanted to investigate this thoroughly before responding.
The reason for the problem is the precise manner that MadGraph treats fermion flow clashes, which was adapted to the UFO model standard from FeynRules - in particular, an anti-fermion (as defined by negative PDG code), always comes before a fermion in an interaction without fermion flow clash. If you reverse the order, the charge-conjugate vertex needs to be used.
A fixed version is under review in a separate MG branch (you can test that branch using Bazaar), but we need to make absolutely sure it doesn't affect any existing models before releasing it.
All the best,
Johan