Failed to reach target in generation of top 1 to 5 decay

Asked by Hesham El Faham

Hi,
I am trying to generate the top decay, t > b e+ e- mu+ vm at LO using the complex mass scheme and mg5 version 2.9.2. I use the default param and run cards, so I don't apply cuts. The code fails to reach target events, it produces no events for one channel (e+ e-) and 1 event for the other (mu+ vm). Below is the code output:
-->
Generating 1000 events with run name run_01
survey run_01
Helicity recycling optimization requires Python3. This optimzation is therefore deactivated automatically.
            In general this optimization speed up the computation be a factor of two.
INFO: compile directory
compile Source Directory
Using random number seed offset = 21
INFO: Running Survey
Creating Jobs
Working on SubProcesses
INFO: P1_t_qlllvl
INFO: Idle: 12, Running: 8, Completed: 0 [ current time: 13h21 ]
INFO: Idle: 11, Running: 8, Completed: 1 [ 2.5s ]
INFO: Idle: 0, Running: 6, Completed: 14 [ 5.9s ]
INFO: Idle: 0, Running: 0, Completed: 20 [ 6.8s ]
sum of cpu time of last step: 59 seconds
  === Results Summary for run: run_01 tag: tag_1 ===

     Width : 0.006449 +- 0.1536 GeV
     Nb of events : 0

INFO: End survey
refine 1000
Creating Jobs
INFO: Refine results to 1000
INFO: Generating 1000.0 unweighted events.
sum of cpu time of last step: 59 seconds
INFO: Effective Luminosity 186065.687646 pb^-1
INFO: need to improve 8 channels
- Current estimate of cross-section: 0.00644933513795 +- 0.153591931179
    P1_t_qlllvl
INFO: Idle: 0, Running: 8, Completed: 0 [ current time: 13h21 ]
INFO: Idle: 0, Running: 5, Completed: 3 [ 3.4s ]
INFO: Idle: 0, Running: 4, Completed: 4 [ 22.3s ]
INFO: Idle: 0, Running: 3, Completed: 5 [ 1m 13s ]
INFO: Idle: 0, Running: 2, Completed: 6 [ 1m 16s ]
INFO: Idle: 0, Running: 1, Completed: 7 [ 1m 20s ]
INFO: Idle: 0, Running: 0, Completed: 8 [ 1m 22s ]
INFO: Combining runs
sum of cpu time of last step: 1m11s
INFO: finish refine
refine 1000 --treshold=0.9
Creating Jobs
INFO: Refine results to 1000
INFO: Generating 1000.0 unweighted events.
sum of cpu time of last step: 1m11s
INFO: Effective Luminosity 8262.34874648 pb^-1
INFO: need to improve 3 channels
- Current estimate of cross-section: 0.145237151815 +- 0.0215240762313
    P1_t_qlllvl
INFO: Idle: 1, Running: 2, Completed: 0 [ current time: 13h22 ]
INFO: Idle: 0, Running: 2, Completed: 1 [ 1m 6s ]
INFO: Idle: 0, Running: 0, Completed: 3 [ 1m 8s ]
INFO: Combining runs
sum of cpu time of last step: 1m11s
INFO: finish refine
INFO: Combining Events
Helicity recycling optimization requires Python3. This optimzation is therefore deactivated automatically.
            In general this optimization speed up the computation be a factor of two.
WARNING: Order of particle in the event did not agree with parent/child order. This might be problematic for some code.
INFO: fail to reach target 1000
  === Results Summary for run: run_01 tag: tag_1 ===

     Width : 0.185 +- 0.03237 GeV
     Nb of events : 1

store_events
INFO: Storing parton level results
INFO: End Parton
reweight -from_cards
decay_events -from_cards
INFO: storing files of previous run
INFO: Done
quit
INFO:
<--
I have no idea what is wrong, may you please help with that?
Best,
Hesham

Question information

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Solved by:
Olivier Mattelaer
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Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

First, Is this make sense to use the complex mass scheme for this computation? This does not sounds natural to me to compute width in that scheme.

Second, what is the mass of the electron/muon, if those mass are zero then you should have a singularity in your matrix-element and your computation can not generate events.

Finally which model are you using?

Cheers,

Olivier

Revision history for this message
Hesham El Faham (helfaham) said :
#2

Thanks for your reply, Olivier.

I am not sure about the complex mass scheme thing. However, the problem persists whether it is True or False.

In fact, I checked, and it turns out that yes the masses of electron and muon are set to zero. I didn't expect that to be a problem in the generation of decays.

This is SM at 5FS. And I think the zero masses of the leptons is fixed by model, is that correct?

Best,
Hesham

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#3

Hi,

> This is SM at 5FS. And I think the zero masses of the leptons is fixed
> by model, is that correct?

please check but i believe that the electron mass is at 0 at the UFO level and that the muon mass is 0 due to the
restrict_default.dat

So I would advise to set a cut to prevent the invariant mass of the dilepton pair to be zero.

Cheers,

Olivier

> On 5 Aug 2021, at 14:45, Hesham El Faham <email address hidden> wrote:
>
> Question #698251 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/698251
>
> Status: Answered => Open
>
> Hesham El Faham is still having a problem:
> Thanks for your reply, Olivier.
>
> I am not sure about the complex mass scheme thing. However, the problem
> persists whether it is True or False.
>
> In fact, I checked, and it turns out that yes the masses of electron and
> muon are set to zero. I didn't expect that to be a problem in the
> generation of decays.
>
> This is SM at 5FS. And I think the zero masses of the leptons is fixed
> by model, is that correct?
>
> Best,
> Hesham
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Hesham El Faham (helfaham) said :
#4

So you mean use the cut in the run card?

Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said :
#5

yes indeed.

Olivier

> On 5 Aug 2021, at 15:00, Hesham El Faham <email address hidden> wrote:
>
> Question #698251 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/698251
>
> Status: Answered => Open
>
> Hesham El Faham is still having a problem:
> So you mean use the cut in the run card?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Hesham El Faham (helfaham) said :
#6

Thanks Olivier Mattelaer, that solved my question.