Catch cases where MadSpin uses BR that don't add up to 1
From @dhirsch
today, we have discovered a bug in the aMC@NLO ttbar samples (see discussion on the top reco mailing list) It turned out that the branching rations for the W boson decay in the param_card didn't add up to one. I.e. the is a typo in two values. However MadSpin basically reported this problem with this line: INFO: Branching ratio to allowed decays: 0.984064
We also have the case of samples generated with gridpacks. In that case the parameter card would be taken from the gridpack. This is the case for the ttH sample (I checked 346443). One can see for this sample that no BR is specified in the parameter card used; then in the header of the lhe file, I see the following values:
DECAY 24 2.046400e+00
# BR NDA ID1 ID2 ...
3.333659e-01 2 -1 2 # 0.68219997776
3.333659e-01 2 -3 4 # 0.68219997776
1.111171e-01 2 -11 12 # 0.22739003344
1.111171e-01 2 -13 14 # 0.22739003344
1.110340e-01 2 -15 16 # 0.2272199776
It's probably these two samples
aMC@NLO+Pythia
410465 aMcAtNloPy8EvtGen_MEN30NLO_A14N23LO_ttbar_noShWe_dil
410464 aMcAtNloPy8EvtGen_MEN30NLO_A14N23LO_ttbar_noShWe_SingleLep