Z+jets matching with misset cut 100 GeV

Asked by Rhitaja Sengupta on 2018-02-01

Hi,

I have a question regarding matching in Z (decaying to nu nu) + 4 jets process (Z+1,2,3,4 jets) , where I generate them with a misset cut of 100 Gev, applied in the MadGraph run_card. The generation was done in the following manner:

define j = j b b~
generate p p > z j ALL=99, z > vl vl~
add process p p > z j j ALL=99, z > vl vl~
add process p p > z j j j ALL=99, z > vl vl~
add process p p > z j j j j ALL=99, z > vl vl~

Matching was performed with xqcut varying in the range 20 - 110 GeV (with MLM matching).

I am facing the following problems:

1. Although I have not generated any Z+0 jet process, still I observe a 0 jet distribution in the DJR plots. It would be extremely helpful if you could explain that or provide a suitable reference regarding this.

2. The DJR2 plot doesn't seem to be continuous and I am getting a significant bump in the plot, the position of which varies with the value of xqcut.

3. DJR3 and DJR4 plots are fine. However the DJR1 is terribly bumpy. I was wondering whether I should be bothered with the DJR1 plot as I have not generated any Z+0 jet process?

4.Would you recommend any xqcut range which will be suitable for the above mentioned process?

Thank you for your help...

Rhitaja

Question information

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Last query:
2018-02-01
Last reply:
2018-02-01

Hi,

> 1. Although I have not generated any Z+0 jet process, still I observe a 0 jet distribution in the DJR plots. It would be extremely helpful if you could explain that or provide a suitable reference regarding this.

The DJR are plotted for QCD jet, some of your diagram includes QED type of jet and therefore event that are associated by our code to such diagram are consider as 0j contribution for the matching/merging algorithm and are therefore consider as 0j contribution by the DJR.

> 2. The DJR2 plot doesn't seem to be continuous and I am getting a significant bump in the plot, the position of which varies with the value of xqcut.

Here are some suggestions:
1) increase the difference between xqcut and qcut, it sometimes happens that the default gap is not enough
2) In some case you have your ptmiss cut which is smaller than qcut (and sometimes even than xqcut) in those
case it does not make any sense to not include the 0j contribution
3) If you fail to have it smooth, you should remove your ptmiss cut and retry without such cut.

> 3. DJR3 and DJR4 plots are fine. However the DJR1 is terribly bumpy. I was wondering whether I should be bothered with the DJR1 plot as I have not generated any Z+0 jet process?

The DJR1 is obviously wrong due to missing the 0j sample. This is expected but this does not mean that this is correct.
(see above)

> 4.Would you recommend any xqcut range which will be suitable for the above mentioned process?

Do not really know actually.

Cheers,

Olivier

> On 1 Feb 2018, at 15:12, Rhitaja Sengupta <email address hidden> wrote:
>
> New question #663959 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/663959
>
> Hi,
>
> I have a question regarding matching in Z (decaying to nu nu) + 4 jets process (Z+1,2,3,4 jets) , where I generate them with a misset cut of 100 Gev, applied in the MadGraph run_card. The generation was done in the following manner:
>
> define j = j b b~
> generate p p > z j ALL=99, z > vl vl~
> add process p p > z j j ALL=99, z > vl vl~
> add process p p > z j j j ALL=99, z > vl vl~
> add process p p > z j j j j ALL=99, z > vl vl~
>
> Matching was performed with xqcut varying in the range 20 - 110 GeV (with MLM matching).
>
> I am facing the following problems:
>
> 1. Although I have not generated any Z+0 jet process, still I observe a 0 jet distribution in the DJR plots. It would be extremely helpful if you could explain that or provide a suitable reference regarding this.
>
> 2. The DJR2 plot doesn't seem to be continuous and I am getting a significant bump in the plot, the position of which varies with the value of xqcut.
>
> 3. DJR3 and DJR4 plots are fine. However the DJR1 is terribly bumpy. I was wondering whether I should be bothered with the DJR1 plot as I have not generated any Z+0 jet process?
>
> 4.Would you recommend any xqcut range which will be suitable for the above mentioned process?
>
> Thank you for your help...
>
> Rhitaja
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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