LO event generation with NLO command with specific light parton

Asked by Sung Hak Lim on 2017-12-13

Dear MG5 team,

I'm trying to understand some initial state dependent feature in my NLO analysis MG5 analysis.

I know this statement is only valid in LO but I checked my distribution scales constant from NLO to LO, so I'm trying to generate LO event with specific initial state.

But I want to generate LO event with seamless parameterization from NLO, i.e. using same run_card and keeping same run output structure.

It could be crazy command but I tried

 generate g g > t t~ [QCD]

Of course, this command is invalid as NLO, but I just wanted to know that using this process to generate LO events after launch by specifying


is okay or not. It seems MG5 gives some output to me at least.

Best wishes,
Sung Hak

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MadGraph5_aMC@NLO Edit question
marco zaro Edit question
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marco zaro
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Best marco zaro (marco-zaro) said : #1

Dear Sung,
yes, if you do only LO runs, the results will be correct. Note that you can generate just the LO matrix elements, and still be able to use the same setup as for your NLO runs, with

generate g g > t t~ [LOonly=QCD]

Finally, note that in the html page after the run you will get the cross section per partonic channel, so you can also use that to get the gg-initiated cross section if you define a process with the multiparticle labels.

Let me know if you need more
Best wishes,


Sung Hak Lim (sunghak-lim) said : #2

Dear Marco,

Thanks for quick answers and suggestions!

LOonly=QCD option seems suitable for my analysis. I'll also check html page after this run then also.

Have a nice day!

Best wishes,
Sung Hak

Sung Hak Lim (sunghak-lim) said : #3

Thanks marco zaro, that solved my question.