MadGraph5_aMC@NLO

Producing events with single particle decay

Asked by Julien Maurer

  Dear authors,

I'm trying to generate a sample of events featuring only a single particle decay, not collisions. For example:
import model mssm
generate x1- > w- n1
output C1_WN1

The "launch C1_WN1" command ignores the number of events specified in the run_card, so I used to call directly bin/generate_events instead. to get a larger sample.

This was working fine in the past, but with the version I'm using today (5.2.2.2), I have problems : calling 'generate_events' results in a crash ("Survey returns zero cross-section"), despite the computation goes on normally via 'launch'.

I suppose something is obsolete now. What alternative can I use to be able to choose the number of events to produce?

In case it's useful, I attach the run/param_card I used, but there's nothing fancy with them. I tested another process (Standard Model this time), a simple top decay into b+W, and here 'generate_events' worked fine.

Thanks a lot,
Julien

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Olivier Mattelaer
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Julien Maurer (jln-maurer) said : 		#1

The run/param cards:

https://drive.google.com/file/d/0B1VV6ev-SL80OUNFSjNKQjlWN2s/view?usp=sharing
https://drive.google.com/file/d/0B1VV6ev-SL80elRGbW9OSzBrbUE/view?usp=sharing

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Olivier Mattelaer (olivier-mattelaer) said : 		#2

Dear Julien,

When I look at the log, I have:

  Couplings of mssm
  ---------------------------------

       GC_419 = -0.00000E+00 -0.00000E+00
       GC_427 = 0.00000E+00 0.00000E+00

So you see that your benchmark forbid your decay.

Also when I use your card, I have the following warning:

WARNING: information about "msoft [21]" is missing using default value: 32337.49.
WARNING: information about "msoft [22]" is missing using default value: -128800.1.
WARNING: information about "mass [23]" is missing using default value: 91.1876.
WARNING: information about "mass [15]" is missing using default value: 1.777.

Cheers,

Olivier

On 25 Mar 2015, at 02:31, Julien Maurer <email address hidden> wrote:

> Question #264127 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/264127
>
> Julien Maurer gave more information on the question:
> The run/param cards:
>
> https://drive.google.com/file/d/0B1VV6ev-SL80OUNFSjNKQjlWN2s/view?usp=sharing
> https://drive.google.com/file/d/0B1VV6ev-SL80elRGbW9OSzBrbUE/view?usp=sharing
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Julien Maurer (jln-maurer) said : 		#3

  Hello Olivier,

Thank you very much for your prompt answer... I'll try to see what's wrong with the param card.

However, if the required couplings are disabled as you say, then I don't understand why the decay width computation provides a non-zero result when ran via 'launch'. What's the difference?

Cheers,
Julien

Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#4

Hi,

> However, if the required couplings are disabled as you say, then I don't
> understand why the decay width computation provides a non-zero result
> when ran via 'launch'. What’s the difference?

I was puzzled too by this, and I try and… it was returning zero as well.
So I have no idea except the hypothesis that you change the param_card at some point.

Cheers,

Olivier

On 25 Mar 2015, at 17:16, Julien Maurer <email address hidden> wrote:

> Question #264127 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/264127
>
> Status: Answered => Open
>
> Julien Maurer is still having a problem:
> Hello Olivier,
>
> Thank you very much for your prompt answer... I'll try to see what's
> wrong with the param card.
>
> However, if the required couplings are disabled as you say, then I don't
> understand why the decay width computation provides a non-zero result
> when ran via 'launch'. What's the difference?
>
>
> Cheers,
> Julien
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Julien Maurer (jln-maurer) said : 		#5

  Hi Olivier,

You're right, sorry, I was tricked by the absence of error/warning messages in the 'launch' case, as well as the fact that the param_card.dat in the output directory is not modified (hence still contains a non-zero value).

Sorry for wasting your time...

Cheers,
Julien

Revision history for this message
Julien Maurer (jln-maurer) said : 		#6

Thanks Olivier Mattelaer, that solved my question.