Code review comment for lp:~maddevelopers/mg5amcnlo/fix_majorana_flipping

Olivier and Tim,

I have redone the implementation in a minimal manner. This way, none of our previous functionality is affected, which I believe is the most safe way to do it (especially considering the *enormous* amount of time I have spent on getting the fermion flow correct for all cases). I certainly don't dare touch that part of the code unless it's absolutely necessary.

My new implementation is minimal and should be self-explanatory. None of the old tests failed (this was the most worrying part of Olivier's implementation - many of the old tests failed, although they should have no relation to this issue), and I added a test - please feel free to go through the test in detail and make sure this is exactly the desired behavior.

Olivier, can you also please run the full set of MSSM parallel tests (in particular, of course, those involving neutralinos), comparing with the old version of MG5 (or MG4, which I think should be equivalent). This is a considerable modification, which new helamp calls whenever there are two different neutralinos and more than 2 final state particles. So it's truly crucial to make sure that the results for regular MSSM have not changed.

I have tested e+ e- > n1 n2 z z, where all relevant conjugated vertices appear, and got identical result with the old MSSM. But I'm not sure enough that this guarantees correctness for all processes.

Many thanks,
Johan