Code review comment for lp:~maddevelopers/mg5amcnlo/3.0.1

Rikkert Frederix (frederix) wrote :

Hi Olivier, Marco,

I looked into the following two issues:

1. The error in the phase-space for the process 'p p > w+ [LOonly=QCD]'.
This is related to the fact that in the 3.0.1 branch the final state W boson is the fks_j particle, while in the 2.6.4 branch it's one of the initial state quarks. However, the phase-space for 2->1 processes with j-fks the massive final state particle does not work. There are divisions by zero everywhere... I'm not sure if there is an easy fix here, apart from telling the code to use an initial state particle as fake j_fks. This will work for the LOonly 2->1 processes. On the other hand, we need to fix this phase-space at some point, since the same is used (and needed!) for the process 'p p > w+ [QED]'.

2. The error for the VETO X-SEC (ickkw=-1).
The whole split-amplitude business has not been implemented for the veto-xsec stuff. I suggest that we do not try to rush this through now, but leave the 3.0.1 code as beta and fix this at a later stage.


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