MadGraph5_aMC@NLO

Fixed order analysis output

Asked by mattcryo

Hello,
I'm trying to study the p p > t t~ process both at parton level, after PS and at hadron level. With ExRootAnalysis I manage to convert the STHEP file to root and run my analysis.
I would like to do the same at parton level, so I turned on the fixed MC option (since, as I have understood, the lhe file contains not physical events). I am able to produce the histograms but I would like to generate a tree as output in order to process it with ROOT.
I have tried to use my analysis routine contained in [PROC_DIR]/FixedOrderAnalysis and I have chosen it in the proper card in order to generate an ASCII file, but putting the open statement in the analysis_begin subroutine, the write one in analysis_fill and the close one in analysis_end does not produce any file in output. Even if I insert a write(*,*) statement no line is printed on screen.

Is there a simple way to produce a tree from a fNLO run or an ASCII file?

Thank you.

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MadGraph5_aMC@NLO Edit question
Assignee:
Rikkert Frederix Edit question
Solved by:
Rikkert Frederix
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Best Rikkert Frederix (frederix) said : 		#1

Hello,

The code runs from several instances simultaneously. The standard output of each of these instances is redirected to the <Your_Process>/SubProcesses/P*/all_G*/log.txt files, and this is where you'll get your output.

Note that when running at fixed order, you do NOT get unweighted events, but rather that each phase-space point comes with a weight (which are not all independent: there are very large correlations among various phase-space points). Also, you'll need a very large number of these phase-space points to get high-statistics distributions. Moreover, you'll need to concatenate all the results of each of the <Your_Process>/SubProcesses/P*/all_G*/ output locations.

Considering the above, it's in general simpler to write your analysis before running the code, and only fill the histograms on the fly.

Best regards,
Rikkert

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mattcryo (mattcryo) said : 		#2

Thank you very much for your reply, you cleared lots of my doubts.
Thank you again

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mattcryo (mattcryo) said : 		#3

Thanks Rikkert Frederix, that solved my question.