WHIZARD

Various errors when generating events with (b) jets in the final state

Asked by Prudhvi Bhattiprolu

Dear Whizard Team,

I am trying to generate events at LO with (b) jets in the final state (using Pythia8 for showering and hadronization) but I am getting one of the following errors:

1) FATAL ERROR: Simulation: failed to generate valid event after 10000 tries (sample_max_tries)

2) FATAL ERROR: Parton 103122 not found in the given model files (similar error with -103122)

3) FATAL ERROR: Parton 203122 not found in the given model files (similar error with -203122 )

where the first error seems to occur with the default SM model file in Whizard, e.g, I've tried e+ e- > Z Z and force Z > b b~ (The corresponding input whizard script "script.sin" and the associated log files are at this link: https://www.dropbox.com/sh/6zk04yqan9h09ug/AACV6bjwaNzL9Gksrs_le0iba?dl=0). And, I seem to get the second and third errors when I'm when using UFO model files with heavy new particles still forced to decay to jets (but without any stable new particles in the final state). On the other hand, processes with heavy new / SM particles decaying to leptons seem to run smoothly without any errors. And the numbers +/- 103122 and 203122 in the last two errors seem to correspond to particle ID's of hadrons "Lambda(1670)0" and "Lambda(1600)bar0" (based on https://pythia.org/latest-manual/ParticleData.html) which are somehow not being recognized by whizard/pythia8. I was also wondering if the first and the other two errors are related? Also, I've tried setting sample_max_tries to 100000 instead of the default value (10000) in which case the event simulation step seems to take an unusually long time (even if the requested number of events is as small as 10) and either returns the same errors or simulate only a few events (far lesser than the requested number of events).

Any help on this would be great!

Thanks a lot,
Prudhvi

Question information

Language:
English Edit question
Status:
Solved
For:
WHIZARD Edit question
Assignee:
Juergen Reuter Edit question
Solved by:
Juergen Reuter
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Best Juergen Reuter (j.r.reuter) said : 		#1

Hi Prudhvi,
these are independent things, I believe. Your second and third problem definitely appear only when using the Whizard-Pythia8 interface and should be completely gone if you let Whizard write out LHE events and pass them to standalone Pythia8. When you use the interface, Whizard needs to know and understand all hadronic states (mesons and baryons), and there are some newer PDG entries which are not yet taken into account in our files. Thanks for pointing this out. For this purpose I created the attached bug report (which I first wrongly assigned to your other question). We will add the additional particles to our particle listing (which is located in share/models/SM_hadrons.mdl ).
For your first issue, I think that comes from the fact that PYTHIA gets stuck on the hadronic decays from Z's that WHIZARD decayed. We haven't checked such a case before and have to look closer into it. Could you try to run write this out as LHE and read it into standalone PYTHIA?

Revision history for this message
Prudhvi Bhattiprolu (prudhvibhattiprolu) said : 		#2

Dear Juergen,

Thank you very much for your reply and all the helpful suggestions! I tried passing the lhe file directly to Pythia8 (via the DelphesPythia8 interface to eventually also get detector-level events) and I am now able to shower+hadronize a large fraction (~70%) of the LHE events generated by Whizard, and the remaining (~30%) events were being rejected by pythia8 raising the following error:

        "Error in ProcessContainer::constructProcess: setting mass failed"

This seems like an issue with Pythia, and I tried changing the particle masses in Pythia (with an input command file) to exactly match with masses defined in the SM model file but the issue still seems to persist. However, if I turn off ISR + beamstrahlung in the Sindarin script, I was able to shower+hadronize all the events in LHE file without any issues. So, I'm not sure about what's going wrong in a subset of events as soon as I switch on ISR+beam effects? Any insights/inputs on this would be great! Also, just in case, I'm attaching my input Whizard script ("script_lhe.sin") which only prints out LHE events, along with input Pythia8 command file ("configLHE.cmnd") and the Pythia log file ("pythia.log") at this link: https://www.dropbox.com/sh/6zk04yqan9h09ug/AACV6bjwaNzL9Gksrs_le0iba?dl=0.

Please let me know if I should instead direct this question to the Pythia team, in which case I will post their comments here as soon as I hear back from them.

Thanks,
Prudhvi

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Prudhvi Bhattiprolu (prudhvibhattiprolu) said : 		#3

Thanks Juergen Reuter, that solved my question.