MadGraph5_aMC@NLO

Generating H + b at NLO stuck at refining results

Asked by Nordin Breugelmans

Dear MadGraph experts,

I am interested in generating the process p p > h b at NLO in QCD. For this I use the loop_sm model with a restriction card that sets the bottom quark mass to zero with a nonzero Yukawa coupling. Then, I use the following command:

generate p p > h b [QCD]

However, after launching the code, I always seem to get stuck at a certain point (e.g. refining results, step 3) where the program sits idle. Even after leaving it running for several hours I occasionally receive another line, but never any more than that. Now I wonder if there is still something being calculated or if the program gets stuck somewhere. Do you have any suggestions?

Thank you in advance,

Nordin

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

The only way to know if the program is dead or computing is to use the tools of the machine/system to monitor cpu activity of the local cpu or the distant one (on cluster).

Now for your process, I'm not sure why you do not include at tree level the b b~ > g h process since at the real level (so NLO accuracy) you should not be able to distinguish this one from g b > h b if you have massless QCD theory. I guess this might not be needed since otherwise the pole would not have cancel. But if this is needed this might also be one reason why the code is struggling to move forward if the pole just fail to detect the issue but that the numerical code hits un-cancel singularity.

Cheers,

Olivier

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