how to keep only final particles

Asked by Piero Viscone

Dear all,
I am generating ttbar semileptonic events with madgraph+madspin

At the end, I found that not only the W's decay products are present, but also the W's themself.

In other words, what I see in LHEs is:

j (incoming particle)
j (incoming particle)

and I want to remove the Ws.
How should I change the cards to don't save them?

My proc_card is:

generate p p > t t~

my madspin_card is:

decay t > b w+, w+ > ell+ vl
decay t~ > b~ w-, w- > q q~

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Piero Viscone (pviscone) said :

I am sorry, I just realized now that this problem is related to CMSSW and not madgraph, mark the question as invalid.
I apologize

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Olivier Mattelaer (olivier-mattelaer) said :

I will answer the question anyway since we indeed wrote such W (I'm actually surprised that you do not have the top as well).
Such answer can always be interesting for others.

We do not have a mode for that in the run_card, especially since in this case, those events are not written by MadEvent but by madspin. So the only option is to hack the code and to remove the lines
line 186 of file MadSpin/

Note that if you do remove those lines, you should not use those events for parton-shower since
1) the color information of the events might not be correct any more (then the parton-shower will crash anyway)
2) the parton-shower will lack information for properly shower the top which can lead to unphysical behaviour.



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