problem with particle ID with pythia

Hi,

Did you include the Branching Ratio information inside the param_card.dat ?
If you want MG5aMC to compute them you can replace the width of that particle to "Auto".
Note that loop induce decay are NOT computed for this computation (i.e. this is not valid for the Higgs in general)

Cheers,

Olivier

> On 15 Jan 2020, at 03:08, Luca <email address hidden> wrote:
>
> New question #687996 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/687996
>
> Hi,
> I am trying to run events using the model ALP_linear_UFO, and I would like to decay the ALP with pythia8. I added to the pythia8_card.dat the following lines
>
> 9000005:all = axion void 0 0 0 0.05 0 0. 0. 0.
> 9000005:addChannel = 1 1. 0 22 22
>
> but somehow pythia does not seem to recognize the particle, as I get these errors when the shower starts
>
> PYTHIA Error: input particle not found in Particle Data Table:
> 9000005:addChannel=1 1. 0 22 22
>
> PYTHIA Error: input particle not found in Particle Data Table:
> 9000005:oneChannel=1 1. 0 22 22
> PYTHIA Abort from Pythia::init: some user particle data did not make sense
> Considering 100 events. Make sure that there is enough events in the input event files, otherwise normalization is likely to be wrong.
>
>
>
> Start generating events
> PYTHIA Abort from Pythia::next: not properly initialized so cannot generate events
>
> May I ask if you know if I have to change something in the pythia card (or elsewhere) such that the particle is recognized?
> Thanks
>
> Luca
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
Thanks for your message. The param card is the one provided by the model, which only says

DECAY 9000005 0.000000e+00 # added

Should I add something there as well, below that?

Hi,

If you want that particle to decay, you need to have a non zero width (as minimum)
and indeed the BR might be needed as well by pythia.

You can set that line to
> DECAY 9000005 Auto # added

and MG5aMC should replace that line by assigning the correct width/BR

Cheers,

Olivier

> On 15 Jan 2020, at 16:57, Luca <email address hidden> wrote:
>
> Question #687996 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/687996
>
> Status: Answered => Open
>
> Luca is still having a problem:
> Hi Olivier,
> Thanks for your message. The param card is the one provided by the model, which only says
>
> DECAY 9000005 0.000000e+00 # added
>
> Should I add something there as well, below that?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

I put these in the param card now

# PDG Width
DECAY 9000005 3.588491e-12
# BR NDA ID1 ID2 ...
   1.108787e-01 2 22 22 # 1

(in principle, I should have access to the correct sets of widths/BR but I put some random numbers now to see if it works) but the inclusion of these lines in the pythia input card

But I keep having problems. If I add only this to the pythia8 card

9000005:all = axion void 0 0 0 0.05 0 0. 0. 0.
9000005:mayDecay = on

I have this error:

Command "generate_events run_16" interrupted with error:
InvalidCmd : Pythia8 shower failed since it did not accept any event from the MG5aMC event file.

I see from the pythia log that the particle does exist

 9000005 axion 0 0 0 5.000e-02 3.588e-12 0.000e+00 0.000e+00 5.48977e-02 1 1 0 1 0
              0 1 0.1108787 100 22 22

but then the log proceeds as

 PYTHIA Error in ResonanceDecays::next: failed to find workable decay channel for id = 9000005
 PYTHIA Abort from Pythia::next: processLevel failed; giving up
 PYTHIA Abort from Pythia::next: reached end of Les Houches Events File
WARNING in MG5aMC_PY8_interface.cc: Reached end of LHEF after 0 Normalisation will be decreased by-100%.

Instead, if I add the information about the BR to the pythia8 card

9000005:all = axion void 0 0 0 0.05 0 0. 0. 0.
9000005:mayDecay = on
9000005:addChannel = 1 1. 0 22 22

I have the same error as above

PYTHIA Error: input particle not found in Particle Data Table:
   9000005:addChannel=1 1. 0 22 22

You should maybe contact Pythia8 authors. They should be able to help you more than me.

Cheers,

Olivier

> On 15 Jan 2020, at 20:43, Luca <email address hidden> wrote:
>
> Question #687996 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/687996
>
> Status: Answered => Open
>
> Luca is still having a problem:
> Hi,
>
> I put these in the param card now
>
> # PDG Width
> DECAY 9000005 3.588491e-12
> # BR NDA ID1 ID2 ...
> 1.108787e-01 2 22 22 # 1
>
> (in principle, I should have access to the correct sets of widths/BR but
> I put some random numbers now to see if it works) but the inclusion of
> these lines in the pythia input card
>
> But I keep having problems. If I add only this to the pythia8 card
>
> 9000005:all = axion void 0 0 0 0.05 0 0. 0. 0.
> 9000005:mayDecay = on
>
> I have this error:
>
> Command "generate_events run_16" interrupted with error:
> InvalidCmd : Pythia8 shower failed since it did not accept any event from the MG5aMC event file.
>
> I see from the pythia log that the particle does exist
>
> 9000005 axion 0 0 0 5.000e-02 3.588e-12 0.000e+00 0.000e+00 5.48977e-02 1 1 0 1 0
> 0 1 0.1108787 100 22 22
>
> but then the log proceeds as
>
> PYTHIA Error in ResonanceDecays::next: failed to find workable decay channel for id = 9000005
> PYTHIA Abort from Pythia::next: processLevel failed; giving up
> PYTHIA Abort from Pythia::next: reached end of Les Houches Events File
> WARNING in MG5aMC_PY8_interface.cc: Reached end of LHEF after 0 Normalisation will be decreased by-100%.
>
> Instead, if I add the information about the BR to the pythia8 card
>
> 9000005:all = axion void 0 0 0 0.05 0 0. 0. 0.
> 9000005:mayDecay = on
> 9000005:addChannel = 1 1. 0 22 22
>
> I have the same error as above
>
> PYTHIA Error: input particle not found in Particle Data Table:
> 9000005:addChannel=1 1. 0 22 22
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
Thanks, I will write them. Thanks a lot for your help
Luca

Hi Luca,
Im facing the same problem and I just want to ask whether you have contacted the pythia8 authors, and what did they say regarding this issue/problem/limitation?

Regards,
Yong Sheng