MadGraph5_aMC@NLO

Error when running susy processes with an external slha file as the param_card.dat file

Asked by Ewan McCulloch

Using the default param_card I have successfully ran MG5 + Pythia8 + Delphes on various susy processes: e.g neutralino-chargino (n2 & x1+) production, gluino pair production. However when I use an external SLHA file the event generation fails before pythia is called. The error message in the command line output is shown below, I have commented in BLOCK CAPITALS where new and old errors are.

INFO: Update the dependent parameter of the param_card.dat
WARNING: Failed to update dependent parameter. This might create trouble for external program (like MadSpin/shower/...)
   <===== THIS ERROR APPEARS WHEN RUNNING WITH THE DEFAULT PARAM_CARD AND DOESN'T CAUSE THE GENERATION TO FAIL
Generating 100 events with run name run_06
survey run_06
INFO: compile directory
WARNING: Missing mass in the lhef file (6) . Please fix this (use the "update missing" command if needed)
ERROR: The width of particle 1000023 is too small for an s-channel resonance (3.1728778e-06). If you have this particle in an s-channel, this is likely to create numerical instabilities . <====== THESE ERRORS ALSO OCCUR WHEN USING DEFAULT PARAM_CARD AND EVENT GENERATION IS SUCCESSFUL
WARNING: Missing mass in the lhef file (6) . Please fix this (use the "update missing" command if needed)
ERROR: The width of particle 1000023 is too small for an s-channel resonance (3.1728778e-06). If you have this particle in an s-channel, this is likely to create numerical instabilities . <====== THESE ERRORS ALSO OCCUR WHEN USING DEFAULT PARAM_CARD AND EVENT GENERATION IS SUCCESSFUL
compile Source Directory
Using random number seed offset = 63
INFO: Running Survey
Creating Jobs
Working on SubProcesses
INFO: P1_qq_n2x1p
INFO: Idle: 0, Running: 0, Completed: 0 [ current time: 17h55 ]
INFO: Idle: 0, Running: 0, Completed: 0 [ current time: 17h55 ]
INFO: End survey
refine 100
Creating Jobs
INFO: Refine results to 100
INFO: Generating 100.0 unweigthed events.
Error when reading /data/atlas/atlasdata/mert3419/software/MSSMproject/TestBuild/MG5_aMC_v2_5_5/neutralino_chargino/SubProcesses/P1_qq_n2x1p/G1.2/results.dat <========= NEW ERRORS DUE TO USING NEW SLHA FILE AS PARAM_CARD
INFO: Effective Luminosity 1.2e+101 pb^-1
INFO: need to improve 0 channels
Error when reading /data/atlas/atlasdata/mert3419/software/MSSMproject/TestBuild/MG5_aMC_v2_5_5/neutralino_chargino/SubProcesses/P1_qq_n2x1p/G1.2/results.dat <========= NEW ERRORS DUE TO USING NEW SLHA FILE AS PARAM_CARD
Survey return zero cross section.
   Typical reasons are the following:
   1) A massive s-channel particle has a width set to zero.
   2) The pdf are zero for at least one of the initial state particles
      or you are using maxjetflavor=4 for initial state b:s.
   3) The cuts are too strong.
   Please check/correct your param_card and/or your run_card.
Zero result detected: See https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-14
quit
INFO:

INFO:

[mert3419@pplxint8 neutralino_chargino]$

END OF OUTPUT

I have added no cuts and the pdfs are not zero so I don't think the problem is with typical reason #2 or #3. Also in the gluino pair production only a gluino is an s-channel particle and I get the same error so I don't think typical reason #1 can be the cause.

Looking at the madgraph directories of others I can see that they have been using slha files just like I am trying to do and have been successful. Has a recent update to MG5 stopped .slha files from being accepted as param_card.dat cards?

An example of an slha file I replaced the param_card.dat card with is found in this tarball https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2014-08/tarfiles/Higgsino.tar.gz, in the example output I showed above the slha file 6755879.slha was used as the parameter card.

This error has been reproduced by my supervisor for multiple slha files and the same p p > n2 + x1+, and p p > go + go processes.

Do you have insight into this?

Best,
Ewan

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Ewan McCulloch
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Revision history for this message
Ewan McCulloch (ewanmcc) said : 		#1

Update, I have talked to someone more familiar with MG5 and he reproduces the error with v2.5.5 and runs MG5 without error with v2.3.3 (another package he happened to have installed). Is there a quick fix here?

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#2

Hi Ewan,

indeed some deep change occur for susy model.
1) the UFO model mssm is removed from the code.
2) if a user still use "import model mssm" the code understand it as "import model_v4 mssm_v4"
3) a new model MSSM_SLHA2 is now available and is the recomended model for SUSY search.
    [this is actually the same model as the previous mssm one, expect that this one needs slha2 format and not a slha1 format automatically translated to slha2]
4) a slha1 to slha2 converter (the one which was used in 2.3.3) is now available on request. via the command
"update to_slha1" (command available at the time of editing the card)
5) since your cards seems to miss some of the mass (like the one of the top), you can also fix that by running "update missing"
such that those parameter will be correctly written in the cards. [please do that AFTER the conversion to slha2]

I have check your process and indeed your param_card crashes with the mssm_v4 model (which is not too surprising since that model is less generic) but works with MSSM_SLHA2

Cheers,

Olivier

Revision history for this message
Ewan McCulloch (ewanmcc) said : 		#3

Cheers for the swift and comprehensive response!

I'll implement your advice and get back to you on whether it's successful.

Many thanks,
Ewan

Revision history for this message
Ewan McCulloch (ewanmcc) said : 		#4

Sorry for being so late here. This indeed fixed my problem,.