Correct DJR plots

[surrutiaquir]

Hi everyone,
I am using MG5+Pythia8 to run some multijet samples, but the DJR plots generated by Pythia are not right. Is there a way to use MA to generate a correct version of them? I have been looking around, but all the MG5 tutorials show plots generated using Pythia6.
Thanks

[jackaraz]

Hi @surrutiaquir, you can check this tutorial. Although it's old, it should still be useful. The manual also provides all the necessary details.

[surrutiaquir]

Hi Jack, Thanks for your prompt response! I found a similar tutorial in my search for information. I think I am too dumb to make the connection between the example there and my own simulation. May I ask for some extra details? Sorry

[surrutiaquir]

I realized that I did not specify my confusion: as in the tutorial, I am simulating the sample with different jet multiplicities using MG5 and running them through Pythia8 (using the MLM algorithm), which yields one merged hepmc file. Is this the sample to be analyzed by MA? Should it be run in hadron or reconstruction mode?
Many thanks again.

[surrutiaquir]

Hi @jackaraz, everyone,

I have made some progress reproducing the example in these slides for the production of W+jets:

import model sm-ckm
define p = g u c d s u~ c~ d~ s~
define j = g u c d s u~ c~ d~ s~
generate p p > w+ @0
add process p p > w+ j @1
add process p p > w+ j j @2
output WPROD
launch WPROD
shower = Pythia8
detector = OFF
analysis = OFF
set nevents 10000
set use_syst False
set iseed 1234
set ickkw 1
set dynamical_scale_choice 3
set no_parton_cut
set xqcut 30
done

The cross section is:

     Cross-section :   9.153e+04 +- 122.8 pb
     Nb of events :  10000
     Matched cross-section :   7.277e+04 +- 382.2 pb
     Nb of events after matching/merging :  7950
     Nb of events after merging :  7950

The script I used in MA is the following:

./bin/ma5 -H
import /Users/surrutiaquir/Software/MG5_aMC_v3_6_2/WPROD/Events/run_01/tag_1_pythia8_events.hepmc.gz
set main.merging.check = true
set main.merging.njets = 2
submit test

However, the DJR plots don't show the individual contributions (see attachment).

What am I doing wrong? I will appreciate any guidance. Thanks, Sebastian
main.pdf

[BFuks]

Hi Sebastian, I think (I am not sure as this is something we did very long ago) that we never implemented them for pythia8. Cheers, Benjamin

…

On 26 Sep 2025, at 19:09, Sebastián Urrutia Quiroga ***@***.***> wrote: Hi @jackaraz <https://github.com/jackaraz>, everyone, I have made some progress reproducing the example in these slides <https://indico.cern.ch/event/555228/sessions/203428/attachments/1315471/1970459/tutorial-CMSandATLAS-2016.pdf> for the production of W+jets: import model sm-ckm define p = g u c d s u~ c~ d~ s~ define j = g u c d s u~ c~ d~ s~ generate p p > w+ @0 add process p p > w+ j @1 add process p p > w+ j j @2 output WPROD launch WPROD shower = Pythia8 detector = OFF analysis = OFF set nevents 10000 set use_syst False set iseed 1234 set ickkw 1 set dynamical_scale_choice 3 set no_parton_cut set xqcut 30 done The cross section is: Cross-section : 9.153e+04 +- 122.8 pb Nb of events : 10000 Matched cross-section : 7.277e+04 +- 382.2 pb Nb of events after matching/merging : 7950 Nb of events after merging : 7950 The script I used in MA is the following: ./bin/ma5 -H import /Users/surrutiaquir/Software/MG5_aMC_v3_6_2/WPROD/Events/run_01/tag_1_pythia8_events.hepmc.gz set main.merging.check = true set main.merging.njets = 2 submit test However, the DJR plots don't show the individual contributions (see attachment). What am I doing wrong? I will appreciate any guidance. Thanks, Sebastian main.pdf <https://github.com/user-attachments/files/22565306/main.pdf> — Reply to this email directly, view it on GitHub <#300 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIWJNJ3TUYS3Q437AK632M33UVXN3AVCNFSM6AAAAACHNOHM3CVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTINJSGQ3DKMQ>. You are receiving this because you are subscribed to this thread.

[surrutiaquir]

Hi Benjamin,

Thanks for your prompt response!

Do you have any suggestions on how to accomplish this (e.g., using a different setup, trying a different generator, etc.)?

The example above is just a toy model, but I need matching/merging for a reliable background simulation.

Many thanks, Sebastian