Pythia8 and matching

[Alexis Kalogeropoulos]

Hello

I ve modified the card to run with pythia like [*] so to enable matching.

However, looks like that all events are accepted in the end so like matching is not working ? Is there any specific way to

[*]
Main:numberOfEvents = 50 ! number of events to generate
Main:timesAllowErrors = 3 ! how many aborts before run stops

! Use same PDFs and alpha_s as in ME calculation.
PDF:pSet = LHAPDF6:NNPDF30_lo_as_0130.LHgrid
SpaceShower:alphaSvalue = 0.130
TimeShower:alphaSvalue = 0.130

! 2) Settings related to output in init(), next() and stat().

Init:showChangedSettings = on ! list changed settings
Init:showChangedParticleData = off ! list changed particle data
Next:numberCount = 100 ! print message every n events
Next:numberShowInfo = 1 ! print event information n times
Next:numberShowProcess = 1 ! print process record n times
Next:numberShowEvent = 0 ! print event record n times

! 3) Set the input LHE file

LHEFInputs:nSubruns = 1
Main:subrun = 0
Beams:frameType = 4
Beams:LHEF = tt_2j_1_1_p263000_r4066.lhe

Next:numberShowEvent = 2

! Specify jet matching parameters for MLM (not necessary!)
JetMatching:merge = on
JetMatching:jetAlgorithm = 2
JetMatching:scheme = 1
JetMatching:setMad = on
JetMatching:qCut = 45.
JetMatching:etaJetMax = 10.0
JetMatching:nJetMax = 2
JetMatching:nQmatch = 5
! Be more forgiving with momentum mismatches.
Check:epTolErr = 1e-2

[Michele Selvaggi]

Hi,

we are not pythia8 experts.
Did you naively try to run your card on standalone pythia8 to see if you get what you expect?
Maybe then we can start see what's happening...

Michele

[Alexis Kalogeropoulos]

yes, the same card with the main89.cc produces matched events. So, what mainXX.cc is executed when one calls ./DelphesPythia8 ? I guess if one could change which pythia module wants to use, that could solve the problem

Another approach - in principle I need the hepmc events, so I could use the hepmc + Delphes where the hepmc has been produced with stand alone p8 . The question is if it is possible then to have in a .root file BOTH the info produced from hepmc+delphes AND the WeightsLHEF derived from the primary LHE file...

thanks

Alexis

[Michele Selvaggi]

I can't look at this now as I am about to take a plane.
If you feel motivated you can debug by looking at readers/DelphesPythia.cpp
That's the main function that gets executed when you run ./DelphesPythia8
If you edit it you have to recompile of course by typing make.

Good luck

[Pavel Demin]

I've just checked main89.cc. It indeed contains some code for matching and merging that we don't have in DelphesPythia8.cpp.

[Alexis Kalogeropoulos]

ok - I will try to edit in place - meanwhile, is there a way to save both LHEF weights from LHE per hepmc event ?

thanks

[Alexis Kalogeropoulos]

so - looks like that there is a problem compiling as the pythia matching routine works with member pointers (*) bit the Delphes implementation using references to pythia (&) . You can find the simplest example in main32.cc - Do you think would it be possible to add the matching functionallity ?

Regards

[Alexis Kalogeropoulos]

Hi

Any possible solution to this ? I mean, if no matching is implemented the Delphes+pythia functionality I guess is of no use for the majority of the users who interface with pythia (as most of the sample nowdays have more than 1partons).

Thanks

PS - I think the simplest case can be seen in the main89 as well

[Michele Selvaggi]

Hi,

we just pushed a new DelphesPythia8 reader.
It should mimic example main32.cc

You have to use main32.cmnd and modify the input LHE file.

Can you try it?
Please let us know if it works.

[Alexis Kalogeropoulos]

Hello

Yes, I ve tried and looks indeed that it is working (of course, one needs to have a proper pythia card with the JetMatching parameters set properly).

Regards