I saw in DJR plots, the plot goes to zero before log(DJR) = 3.0 value. But in my DJR1 plot for e- e+ > t t~ + jets , the plot continues after 3.0. Is it correct?

[Reza Jafari]

Dear experts,

I am working on a project on top quark at the electron-positron colliders, e-e+ -> ttbar+(jet) where I have to perform merging.
I performed the MLM matching and for sanity check I prepared the DJR plots. I would be very much grateful if you help me with the following explanation and give advice.

- I plotted the DJR1 figure for e- e+ > t t~ + jets process. In our DJR1 plot (0 jet sample -> 1 jet sample), the range of DJR parameter is not like the others. In my DJR2, DJR3 (and also DJR1 in other processes that I saw in some presentations), plots go to zero before log(DJR) = 3.0. But in my DJR1 plot, it continues after 3.0 value. I am not sure whether this plot is correct or not?
If log(DJR1) can take values larger than 3.0, how can we change the range of the parameter in the plot?

- In order to compare the results of matching (just for 0-jet and 1-jet samples), I chose different values for xqcut (in Madgraph run card) and qCut (in pythia card). I prepared DJR plot for below values:
xqcut = 10 , qCut = 10
xqcut = 20 , qCut = 20
xqcut = 20 , qCut = 30
I don't have any idea which values for xqcut and qCut parameters are the best? And which plot is suitable for an acceptable matching? I think all plots are smooth with little differences.

I would greatly appreciate any assistance or advice you could offer me.

Thank you very much for your time.
Best regards,

Reza

PS.
Some more details of what we have done are as follows.

MadGraph:
C.M. energy = 3 TeV
generate e- e+ > t t~ @0
add process e- e+ > t t~ j @1
add process e- e+ > t t~ j j @2
add process e- e+ > t t~ j j j @3
ickkw = 1, xqcut = 10 or 20 or ... , qCut = 10 or 20 or 30, ...

MadAnalysis:
bin/ma5 -H
ma5> install fastjet
ma5> import <path-to-the-event-file>/pythia_events.hep.gz as ttjets
ma5> set main.merging.check = true
ma5> set main.merging.njets = 3 (for our purpose = 1)
ma5> submit output

[Reza Jafari (reza13)]

In our DJR2, DJR3 (and also DJR1 in other processes) plots go to zero before log(DJR) = 3. But in our DJR1 plot, it continues after 3 value. I am not sure whether this plot is correct or not?

[Reza Jafari (reza13)]

Attachment explanations:

10_10.png : xqcut = 10 , qCut = 10
20_20.png : xqcut = 20 , qCut = 20
20_30.png : xqcut = 20 , qCut = 30

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

For MLM merging, you need to have QCUT strictly bigger than xqcut (we advise AT least 10GeV of difference, and I found cases where 10GeV was actually not enough (for higgs production).

For the rest, this is not surprising that DJR1 has larger scale than DJR2 (like DJR2 drops later than DJR3).

If you take the "naive" idea that DJR plot correspond to the PT of the corresponding jet, it is indeed natural that the second jet has a smaller PT than the first jet.

Now for such fix energy, I would expect that you could use QCUT of the order of 100 GeV, but I have actually no experience in MLM for lepton-collider.

Cheers,

Olivier

[Reza Jafari (reza13)]

Dear Olivier,

Thanks a lot for your useful response.

Actually I prepared DJR plots for very different values of xqcut and QCUT from 10 to 60 for both. For example see the new attachment for xqcut = 30 and QCUT = 60 (30_60.png). I will extend QCUT value to 100 GeV as you suggested and let you know the result. Anyway I still could not change the range of x axis more than 3.0 in DJR plot to see the tail of the plot.

The main problem is that I expected (for example in 20_30.png) the blue line (0-jet sample) go to zero around the peak of the red line (1-jet sample) to distinguish between PS and ME. But it did not happen. Do you have any idea about it?

I would greatly appreciated for your time and advises.

Best Regards,

Reza

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

> Anyway I still could
> not change the range of x axis more than 3.0 in DJR plot to see the tail
> of the plot.

That is not a question for me, but for the MadAnalysis5 team.

> The main problem is that I expected (for example in 20_30.png) the blue
> line (0-jet sample) go to zero around the peak of the red line (1-jet
> sample) to distinguish between PS and ME. But it did not happen. Do you
> have any idea about it?

Most tools are not able to plot the TRUE DJR plot. They are typically plotting proxies...
Which makes it difficult for validation.
This is why I liked to validate MLM with pythia6 and madanalysis4 since that plot was the True DJR.
PY8 authors themself claims that they can not plot the True DJR for pythia8 ( i do not think this is true but this is what they claim)

Cheers,

Olivier

> On 3 Mar 2020, at 11:46, Reza Jafari <email address hidden> wrote:
>
> Dear Olivier,
>
> Thanks a lot for your useful response.
>
> Actually I prepared DJR plots for very different values of xqcut and
> QCUT from 10 to 60 for both. For example see the new attachment for
> xqcut = 30 and QCUT = 60 (30_60.png). I will extend QCUT value to 100
> GeV as you suggested and let you know the result. Anyway I still could
> not change the range of x axis more than 3.0 in DJR plot to see the tail
> of the plot.
>
> The main problem is that I expected (for example in 20_30.png) the blue
> line (0-jet sample) go to zero around the peak of the red line (1-jet
> sample) to distinguish between PS and ME. But it did not happen. Do you
> have any idea about it?
>
> I would greatly appreciated for your time and advises.
>
> Best Regards,
>
> Reza
>
>
>
>
> ** Attachment added: "30_60.png"
> https://bugs.launchpad.net/mg5amcnlo/+bug/1865848/+attachment/5333020/+files/30_60.png
>
> --
> You received this bug notification because you are subscribed to
> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1865848
>
> Title:
> I saw in DJR plots, the plot goes to zero before log(DJR) = 3.0 value.
> But in my DJR1 plot for e- e+ > t t~ + jets , the plot continues after
> 3.0. Is it correct?
>
> Status in MadGraph5_aMC@NLO:
> New
>
> Bug description:
> Dear experts,
>
> I am working on a project on top quark at the electron-positron colliders, e-e+ -> ttbar+(jet) where I have to perform merging.
> I performed the MLM matching and for sanity check I prepared the DJR plots. I would be very much grateful if you help me with the following explanation and give advice.
>
> - I plotted the DJR1 figure for e- e+ > t t~ + jets process. In our DJR1 plot (0 jet sample -> 1 jet sample), the range of DJR parameter is not like the others. In my DJR2, DJR3 (and also DJR1 in other processes that I saw in some presentations), plots go to zero before log(DJR) = 3.0. But in my DJR1 plot, it continues after 3.0 value. I am not sure whether this plot is correct or not?
> If log(DJR1) can take values larger than 3.0, how can we change the range of the parameter in the plot?
>
> - In order to compare the results of matching (just for 0-jet and 1-jet samples), I chose different values for xqcut (in Madgraph run card) and qCut (in pythia card). I prepar...

[Reza Jafari (reza13)]

Dear Olivier,

Thanks again.

I used pythia6 and madanalysis5. I am trying with ma4 and Matchchecker package to compare the results.
I will send the problem of x axis DJR plot to madanalysis team.

Regards

Reza