Combine HwU distributions from both Pythia8 and MADatNLO analyses

Asked by Hesham El Faham on 2021-04-05

Hi,
I have a simple question regarding HwU plotting. I am trying to combine HwU distributions from a py8 analysis with another from a nlo fixed order analysis. For this I use the usual command:
--> python /bin/internal/histrograms.py < the MADatNLO.HwU> <the plot_PYTHIA8_1_0.HwU> etc <--
apparently what happens is that pythia8 HwUs are combined together and fixed order ones are combined together but both fixed order and py8 distributions don't come up in the same plot. I am wondering if I am missing something here, I want to get out a simple plot with NLO and NLO+PS distributions.

Sorry for the trivial question but I can't figure it out. Your help is much appreciated.
Best,
Hesham

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Rikkert Frederix Edit question
Solved by:
Rikkert Frederix
Solved:
2021-04-12
Last query:
2021-04-12
Last reply:
2021-04-12
Rikkert Frederix (frederix) said : #1

Dear Hesham,

Do the histograms that you want to have in the same plot have exactly the same name?

Best,
Rikkert

Hesham El Faham (helfaham) said : #2

Dear Rikkert,

Yes, they have the same name. Only one histogram has the same name in the two analyses but not the same blank spaces afterwards.

Best,
Hesham

Rikkert Frederix (frederix) said : #3

Dear Hesham,

What happens if you edit the .HwU files and give them exactly the same names? Does that work?

If not, it might actually also be a problem if in some of the files you do have multiple columns to deal with the scale (or PDF) uncertainties, while in the other file you do not have them. Might that be the problem?

best,
Rikkert

Hesham El Faham (helfaham) said : #4

Dear Rikkert,

Changing the name of the files didn't work.

On the other hand, it is true that the py8 HwU files don't have the scale uncertainties, while I do have these uncertainties in the fixed order ones. Is there a way to control this?

I tried turning off all uncertainties in the plotting command --no_scale, etc. but that didn't work.

Best,
Hesham

Rikkert Frederix (frederix) said : #5

Dear Hesham,

I'm afraid that with the current version of the histogram.py code you cannot combine HwU files with different number of weights. (I.e., some setups with scale uncertainties and others without). Easiest is to make sure that you always plot with the same setup. If that is too time-consuming or otherwise wasteful, you could also try parsing the HwU file that have the scale uncertainties and remove the corresponding columns from those files. Or add columns with some "random" numbers to the other files.

Best,
Rikkert

Hesham El Faham (helfaham) said : #6

Dear Rikkert,

Thank you for your reply. I follow now.

Is their a way to turn off the showering in the shower card? I.e. reproduce the fixed order results with the py8 analysis? I tried naively setting nevents in the shower to zero thinking that might be the way, but I produced empty plots. I think this is the easiest way to follow the same setup.

Best,
Hesham

Best Rikkert Frederix (frederix) said : #7

Dear Hesham,

You cannot reproduce fixed-order results with event generation: in the MC@NLO formalism, the short-distance cross section is not equal to the fixed-order NLO one.

Best,
Rikkert

Hesham El Faham (helfaham) said : #8

Thanks Rikkert Frederix, that solved my question.