Main Web>DerSchrecklicheSven>AthenaStuff>McEventCollection (2005-01-12, AndreasWildauer)

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".

-- DerSchrecklicheSven - 12 Jan 2005