CalcHEP

pythia8 not able to generate hepmc file from calchep lhe file

Asked by Siddharth

hi,
       I tried using pythia to generate hepmc file using the .lhe output from calchep. I get a zero size hepmc file as output with no event listings. However the same code does ok for an lhe file generated from madgraph. I am trying to generate a process

                           a, a -> b, b~, b, b~ using laser photons in calchep where a = photon, b = b quark and b~ = b-bar

Could you please suggest as to what might be the problem and how can it be corrected ?

regards

Siddharth

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Alexander Belyaev (alexander.belyaev) said : 		#2

Sorry for getting late to you and thanks for reporting the problem.
To solve the problem we need to know how exactly you have been trying to generate HEPMC file.
Please send relevant files and scripts to me -- <email address hidden>
Thanks
Alexander

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Alexander Belyaev (alexander.belyaev) said : 		#4

Dear Siddharth,

The key message from PYTHIA is
PYTHIA Error in BeamRemnants::Add: failed to find physical colour state after colour reconnection

Which most likely means that the invariant bb-bar mass for the events always below 9 GeV or so,
Pythia can not generate b-bar hadron state.
Please check invariant mass for bb-bar state
and establish the minimal cut if necessary.

I did not have time to run more detailed checks,
will do when I have time.
But this the first place I will look at to resolve the problem.

Regards,
Alexander