Generating exclusive Monte Carlo data

Todo

Write contextual introduction.

Designing decay cards

When generating a Monte Carlo sample, a decay card (usual extension: dec) can be used to overwrite the decay of certain particles. This allows you to generate a Monte Carlo sample that only contains events with the signal topology which you are studying.

A decay card is a text file that lists certain particle decays. If your decay card specifies the decay channels of a certain particle, the ‘normal’ decay channels (those listed in the PDG) for that particle will be overwritten. The decay channels of one particle should follow this pattern:

Decay <particle name>
  <branching fraction 1> <daughter 1a> <daughter 1b> <generator> <parameters>;
  <branching fraction 2> <daughter 2a> <daughter 2b ><generator> <parameters>;
Enddecay

Here, there are only two decay channels, but you can add more of course. Note that a decay card has to end with the line:

End

Warning

Due to a small bug in BOSS, a decay card has to end in with an empty white line, otherwise the simulation job will crash.

If you do not specify the decay channels of a certain particle, the decay card called DECAY.dec in the BesEvtGen package will be used. This file essentially follows the PDG listings. In addition, definitions of particles (including their physical widths) can be found in the file pdt.table. Both files are located here (in the case of BOSS 7.0.4):

/cvmfs/bes3.ihep.ac.cn/bes3sw/Boss/7.0.4/Generator/BesEvtGen/BesEvtGen-00-03-98/share