PYTHIA: If you notice strange looking decays ...
... when doing GenEvent->print(). That is
normal.
E.g.: I noticed a W+ decay like this when looking for Ws:
Vertex: -9 ID: 0 (X,cT)=+2.12e-02,+2.62e-03,-1.08e+02,+0.00e+00
I: 1 10 24 -2.91e+04,+6.55e+04,+1.38e+05,+1.76e+05 3 -9
O: 3 16 -13 +2.65e+04,+3.93e+04,+5.66e+04,+7.39e+04 3 -11
22 24 -2.92e+04,+6.52e+04,+1.37e+05,+1.75e+05 2 (nil)
17 14 -5.57e+04,+2.58e+04,+8.06e+04,+1.01e+05 3 -12
Apparently the W+ decays into mu+ W+ munu!!
In Pythia by default the W before corrected for the parton shower is also kept (see variable mstp(128)).
This setting was used for DC2 and in the future. DC1 was with another setup.
Anyway, the W before the parton correction (in this case with the barcode 22 and no decay vertex (nil)) is "useless".
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DerSchrecklicheSven - 12 Jan 2005