MadGraph5_aMC@NLO

loop MSSM

Asked by Khalida Hendricks

Hello,

I previously used MG5_aMC_v2_3_3 with the loop_MSSM model to generate events for g g > go n1 [QCD]. I have upgraded to MG5_aMC_v2_5_2 and the loop_MSSM model is no longer in the package. I tried MSSM_SLHA2 which came back with an error saying it could not handle loop processes:

"generate g g > go n1 [QCD]" with error: InvalidCmd : The model MSSM_SLHA2 cannot handle loop processes

 I tried copying my old loop_MSSM to the models file and got a series of errors during event generation:

Channel [x] has encountered a fraction of [0.XXXX] of numerically unstable loop matrix element computations (which could not be rescued using quadruple precision).

Is there a model compatible with MG5_aMC_v2_5_2 that can perform loop MSSM calculations or do I need to go back to the previous version of MadGraph to do this?

Thank you.

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

The loop_MSSM model of version 2.3.3 should never have been released with any version of MG5aMC.
This was an error in the release of that version. This model is known to contain error and produce invalid result.
IT SHOULD NOT BE USED FOR PUBLICATION!

If you want to use NLO model in the context of MSSM, I would refer to the following article:
​arXiv:1510.00391 <http://arxiv.org/abs/1510.00391>

The associated UFO model is available at the following page:
http://feynrules.irmp.ucl.ac.be/wiki/NLOModels

Cheers,

Olivier

On 27 Mar 2017, at 17:27, Khalida Hendricks <<email address hidden><mailto:<email address hidden>>> wrote:

New question #593698 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/593698

Hello,

I previously used MG5_aMC_v2_3_3 with the loop_MSSM model to generate events for g g > go n1 [QCD]. I have upgraded to MG5_aMC_v2_5_2 and the loop_MSSM model is no longer in the package. I tried MSSM_SLHA2 which came back with an error saying it could not handle loop processes:

"generate g g > go n1 [QCD]" with error: InvalidCmd : The model MSSM_SLHA2 cannot handle loop processes

I tried copying my old loop_MSSM to the models file and got a series of errors during event generation:

Channel [x] has encountered a fraction of [0.XXXX] of numerically unstable loop matrix element computations (which could not be rescued using quadruple precision).

Is there a model compatible with MG5_aMC_v2_5_2 that can perform loop MSSM calculations or do I need to go back to the previous version of MadGraph to do this?

Thank you.

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