the case of SM Higgs boson production in the H → ZZ decay channel in the four-lepton final state

Hi,

I would say that you have issue with your signal/background definition.
Since your signal is a subset of the Feynman diagram present in your background.

Next issue here is that you ask to have two onshell Z which is certainly not something that you want to ask to make the plot that you want to reproduce (they have m4ll going from 80 GeV).

So I guess that your main issue here is the proper definition of what is called ZZ and what is called H.

Cheers,

Olivier

> On 30 Aug 2023, at 09:10, geyao <email address hidden> wrote:
>
> New question #707782 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/707782
>
> Dear Developers,
>
> I want to simulate an example from the ATLAS official website using MadGraph and Delphes：the case of SM Higgs boson production in the H → ZZ decay channel in the four-lepton final state, The specific link is http://opendata.atlas.cern/release/2020/documentation/physics/FL2.html. In the official provided analysis code, we can find the background and signal as follows(I just care about these two parts) :
>
> r'Background $ZZ^*$' : { # ZZ
> 'list' : ['llll'],
> 'color' : " #00cdff"# red
> },
>
> r'Signal ($m_H$ = 125 GeV)' : { # H -> ZZ -> llll
> 'list' : ['ggH125_ZZ4lep','VBFH125_ZZ4lep','WH125_ZZ4lep','ZH125_ZZ4lep'],
> 'color' : "#ff0000" # light blue
> },
>
> I want to plot some graphs that look exactly identical to ATLAS using the data simulated by Delphes. So I simulated the following process.
>
> background:
> import model heft
> output bkg
> generate p p > z z, z > l+ l-
> launch
> ...
> bgk/Cards/delphes_card_ATLAS.dat
>
> signal:
> import model heft
> generate p p > h > z z, z > l+ l-
> output sgn
> launch
> ...
> sgn/Cards/delphes_card_ATLAS.dat
>
> Then, I analyzed and plotted the simulated data. But the graph I drew is very different from what was expected. For example, on the x-axis, we have PT, and on the y-axis, we have Events. The vertical axis of the histogram is much larger than anticipated, about three to four times bigger, and in certain intervals, the ratio between the signal and background also exceeds expectations by a significant margin.You can find detailed information from the link provided below：https://pan.baidu.com/s/1C2vsqXI_cbXkKpKe6L9P9w?pwd=ymyx
> password：ymyx
>
> The formula for getting the final weight is: lumi×xsec×Weight/sumw
>
> Initially, I suspected that there was an inconsistency in the luminosity between the signal and background. However, I realized that the two processes I simulated were unable to fix the luminosity at 10fb-1, as required in the ATLAS example. This led me to suspect that there might be an issue with the simulation process itself. Unfortunately, I’m unsure which specific process needs to be simulated or which parameters need to be modified.
>
> Can someone tell me what process this should simulate? Or did I make a mistake somewhere?
>
> Thanking you in advance!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Oliver,

Thanks for your reply!

I have to admit that I am a newbie in particle physics. I think that ZZ refers to a pair of Z bosons, and H represents the Higgs boson. And they are all generated by the collision of two protons, then they decay into four leptons finally, isn’t it?

I believe the two processes I simulated are not what I intended, but I am unsure which specific processes ATLAS’s example requires. I just want to replicate the ATLAS example using MadGraph. Do you have any suggestions or opinions on this matter? Which process do you think corresponds to the background and which one corresponds to the signal?

Thanks,

Geyao

The best is likely to read the actual paper for that plot.

maybe something like
p p > z > l+ l- l+ l- / h
for background
and got signal
p p > h , h > z > l+ l- l+ l-

would be enough but I have not think enough on it to be sure.

Cheers,

Olivier

> On 30 Aug 2023, at 10:45, geyao <email address hidden> wrote:
>
> Question #707782 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/707782
>
> Status: Answered => Open
>
> geyao is still having a problem:
> Hi Oliver,
>
> Thanks for your reply!
>
> I have to admit that I am a newbie in particle physics. I think that ZZ
> refers to a pair of Z bosons, and H represents the Higgs boson. And they
> are all generated by the collision of two protons, then they decay into
> four leptons finally, isn’t it?
>
> I believe the two processes I simulated are not what I intended, but I
> am unsure which specific processes ATLAS’s example requires. I just want
> to replicate the ATLAS example using MadGraph. Do you have any
> suggestions or opinions on this matter? Which process do you think
> corresponds to the background and which one corresponds to the signal?
>
> Thanks,
>
> Geyao
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.