Hadronize b quark in Pythia from LHE file

You should contact Pythia author about this.

I do not know how to help you,

Sorry,

Olivier

> On 28 Feb 2019, at 00:53, saneli carbajal vigo <email address hidden> wrote:
>
> New question #678840 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/678840
>
> Hello,
>
> I want to produce events of the process
>
> vm b > mu- t, (t > b w+, w+ > mu+ vm)
>
> in Madgraph and then hadronise the resulting "b" in pythia. I have set the PDFs of both vm and b to 0 (no PDF).
>
> I undestand I can call pythia8 directly within Madgraph, but I instead I want to feed the lhe output of Madgraph to pythia externally (with a simple c++ script) and hadronise the b quark directly in pythia (following one of the sample main programs, main11, of pythia8).
>
> However, when I try to generate the events in pythia I get an error related to the beams: it seems like pythia8 can't handle the neutrino and bottom beams used by madgraph, which in retrospective makes sense.
>
> Is there any way to get around this and hadronise the b quarks obtained in madgraph?
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hello,

So I gave up and I have tried to hadronize the b quark within madgraph, but pythia8 returns the same error.
What I've done is:

MG5_aMC>generate vm b > mu- t, (t > b w+, w+ > mu+ vm)
MG5_aMC>output 02
MG5_aMC>launch 02

And chosen pythia8 for shower. I'm running 1000 events (with the PDFs of both beams set to 0 in the run_card).

However, madgraph freezes at:

INFO: Running Pythia8 [arXiv:1410.3012]
Splitting .lhe event file for PY8 parallelization...
Submitting Pythia8 jobs...
Pythia8 shower jobs: 1 Idle, 0 Running, 0 Done [0 second]

At first I thought the parallelization was the problem, so I did:

MG5_aMC>set nb_core 1

and launched the process again. This time I checked at the tag1_pythia8.log file and this is what I found:

 *----------------------- SusyLesHouches SUSY/BSM Interface ------------------------*
 | Last Change 12 Apr 2017 - P. Skands
 | Parsing: unweighted_events.lhe.gz
 | (SLHA::readFile) line 453 - storing non-SLHA(2) block: yukawa
 *------------------------------------------------------------------------------------*
 PYTHIA Info from SLHAinterface::initSLHA: No MODSEL found, keeping internal SUSY switched off
 PYTHIA Info from SLHAinterface::initSLHA: importing MASS entries for id = {25}
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring MASS entries for id = {1,2,3,4,5,6,11,12,13,14,15,16,21,22,23,24} (SLHA:keepSM. Use id > 1000000 for new particles)
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring DECAY tables for id = {6,23,24,1,2,3,4,5,11,12,13,14,15,16,21,22} (SLHA:keepSM. Use id > 1000000 for new particles)
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring empty DECAY tables for id = {25} (total width provided but no Branching Ratios)
 PYTHIA Error in Pythia::init: cannot handle this beam combination
 PYTHIA Abort from Pythia::init: checkBeams initialization failed
Counting events in input LHEF, please wait.
Found 1000 events in input LHEF.

Start generating events
 *----------------------- SusyLesHouches SUSY/BSM Interface ------------------------*
 | Last Change 12 Apr 2017 - P. Skands
 | Parsing: unweighted_events.lhe.gz
 | (SLHA::readFile) line 453 - storing non-SLHA(2) block: yukawa
 *------------------------------------------------------------------------------------*
 PYTHIA Info from SLHAinterface::initSLHA: importing MASS entries for id = {25}
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring MASS entries for id = {1,2,3,4,5,6,11,12,13,14,15,16,21,22,23,24} (SLHA:keepSM. Use id > 1000000 for new particles)
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring DECAY tables for id = {6,23,24,1,2,3,4,5,11,12,13,14,15,16,21,22} (SLHA:keepSM. Use id > 1000000 for new particles)
 PYTHIA Warning in SLHAinterface::initSLHA: ignoring empty DECAY tables for id = {25} (total width provided but no Branching Ratios)
 PYTHIA Abort from Pythia::next: not properly initialized so cannot generate events

¿Does this mean that pythia is not well configured or perhaps it's a bug?

Hi,

We do not have any smart mode to setup the pythia8 card correctly for such type of generation.
So you will need to setup the various pythia8 parameter correctly to have this running.
I personally do not know PY8 well enough to help you on how to set such parameter.
So my only suggestion is again to contact PY8 author.

Actually the issue of using py8 inside or outside MG5aMC does not help in any way for your process.

Cheers,

Olivier

> On 28 Feb 2019, at 20:07, saneli carbajal vigo <email address hidden> wrote:
>
> Question #678840 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/678840
>
> Status: Answered => Open
>
> saneli carbajal vigo is still having a problem:
> Hello,
>
> So I gave up and I have tried to hadronize the b quark within madgraph, but pythia8 returns the same error.
> What I've done is:
>
> MG5_aMC>generate vm b > mu- t, (t > b w+, w+ > mu+ vm)
> MG5_aMC>output 02
> MG5_aMC>launch 02
>
> And chosen pythia8 for shower. I'm running 1000 events (with the PDFs of
> both beams set to 0 in the run_card).
>
> However, madgraph freezes at:
>
> INFO: Running Pythia8 [arXiv:1410.3012]
> Splitting .lhe event file for PY8 parallelization...
> Submitting Pythia8 jobs...
> Pythia8 shower jobs: 1 Idle, 0 Running, 0 Done [0 second]
>
> At first I thought the parallelization was the problem, so I did:
>
> MG5_aMC>set nb_core 1
>
> and launched the process again. This time I checked at the
> tag1_pythia8.log file and this is what I found:
>
>
> *----------------------- SusyLesHouches SUSY/BSM Interface ------------------------*
> | Last Change 12 Apr 2017 - P. Skands
> | Parsing: unweighted_events.lhe.gz
> | (SLHA::readFile) line 453 - storing non-SLHA(2) block: yukawa
> *------------------------------------------------------------------------------------*
> PYTHIA Info from SLHAinterface::initSLHA: No MODSEL found, keeping internal SUSY switched off
> PYTHIA Info from SLHAinterface::initSLHA: importing MASS entries for id = {25}
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring MASS entries for id = {1,2,3,4,5,6,11,12,13,14,15,16,21,22,23,24} (SLHA:keepSM. Use id > 1000000 for new particles)
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring DECAY tables for id = {6,23,24,1,2,3,4,5,11,12,13,14,15,16,21,22} (SLHA:keepSM. Use id > 1000000 for new particles)
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring empty DECAY tables for id = {25} (total width provided but no Branching Ratios)
> PYTHIA Error in Pythia::init: cannot handle this beam combination
> PYTHIA Abort from Pythia::init: checkBeams initialization failed
> Counting events in input LHEF, please wait.
> Found 1000 events in input LHEF.
>
> Start generating events
> *----------------------- SusyLesHouches SUSY/BSM Interface ------------------------*
> | Last Change 12 Apr 2017 - P. Skands
> | Parsing: unweighted_events.lhe.gz
> | (SLHA::readFile) line 453 - storing non-SLHA(2) block: yukawa
> *------------------------------------------------------------------------------------*
> PYTHIA Info from SLHAinterface::initSLHA: importing MASS entries for id = {25}
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring MASS entries for id = {1,2,3,4,5,6,11,12,13,14,15,16,21,22,23,24} (SLHA:keepSM. Use id > 1000000 for new particles)
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring DECAY tables for id = {6,23,24,1,2,3,4,5,11,12,13,14,15,16,21,22} (SLHA:keepSM. Use id > 1000000 for new particles)
> PYTHIA Warning in SLHAinterface::initSLHA: ignoring empty DECAY tables for id = {25} (total width provided but no Branching Ratios)
> PYTHIA Abort from Pythia::next: not properly initialized so cannot generate events
>
>
> ¿Does this mean that pythia is not well configured or perhaps it's a bug?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.