MadGraph5_aMC@NLO

Spin information from MadSpin

Asked by Dominic Hirschbuehl

Dear MadSpin authors,

We are using MadSpin to decay t-channel single top events (produced with aMC@NLO or Powheg).
As we saw from our first samples, the spin of the particles are not written out in the LHE-files.
This is particularly important for the decay of tau, which is handeled either by Tauola or the shower generator.
Since it is not written out, the decayed taus are not polarized.

We found out, that instead of a 0 for the SPINUP variable a 9 would be written out, Pythia8 could do
the backward engenieering and produce polarized taus.

Would it be possible to change this or add an option to MadSpin?

Thanks in advance
  Dominic

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Pierre Artoisenet Edit question
Solved by:
Pierre Artoisenet
Solved:
Last query:
Last reply:
Revision history for this message
Best Pierre Artoisenet (partois) said : 		#1

Dear Dominic,

Indeed, the spin information of the final state particles is not included in the output of MadSpin.

If I understand correctly the last part of your message you just want to change the format of the
events written by MadSpin (without changing the way events are generated). To do that, you can modify
the routine get_particle_line in the file MadSpin/decay.py (around line 183)

Let me know if you have any problem with the modification,

Cheers,

Pierre

Revision history for this message
Dominic Hirschbuehl (hirsch-t) said : 		#2

Thanks Pierre Artoisenet, that solved my question.