# madgraph+shower

Dear experts,

I want to study the parton shower effect on p p > z z h [QCD]. So I generate the events in the following. There are two options that I don't know how to set.

generate p p > z z h [QCD]

output pp-zzh-test

launch

/======

| 1. Type of perturbative computation order = NLO |

| 2. No MC@[N]LO matching / event generation fixed_order = OFF |

| 3. Shower the generated events shower = PYTHIA8 |

| 4. Decay onshell particles madspin = OFF |

| 5. Add weights to events for new hypp. reweight = OFF |

| 6. Run MadAnalysis5 on the events generated madanalysis = OFF |

\======

enter

Then, in the run_card.dat there is a ickkw option, and I don't know which one is suitable for my current study.

#******

# ickkw parameter: *

# 0: No merging *

# 3: FxFx Merging - WARNING! Applies merging only at the hard-event *

# level. After showering an MLM-type merging should be applied as *

# well. See http://

# 4: UNLOPS merging (with pythia8 only). No interface from within *

# MG5_aMC available, but available in Pythia8. *

# -1: NNLL+NLO jet-veto computation. See arxiv:1412.8408 [hep-ph]. *

#******

0 = ickkw

In the shower_card.dat, how to correctly set these two options.

# FxFx merging parameters !ONLY FOR PYTHIA8!

#******

Qcut = -1.0 # Merging scale

njmax = 0 # Maximal multiplicity in the merging

#******

Thanks!

Huanyu Bi

## Question information

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- Status:
- Answered

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- Last query:
- 2018-12-22

- Last reply:
- 2018-12-22

From the information that I see in your mail.

I would say that one correct option is to keep ickkw=0

and the two others parameter are then fine as well.

Now I do not know how you will handle those samples. If you want to merge those with other samples generated with

p p > z z h j [QCD]

Then obviously the above choice is not appropriate.

Cheers,

Olivier

HuanyuBi (bihuanyu) said : | #2 |

Dear Olivier,

Thank you for your answer. I don't plan to merge pp>zzh [QCD] with pp>zzhj. I have another problem.

I want to compare some differential distribution, e.g, the transverse momentum of higgs (PT(h1)) before and after parton shower. I use ma5

>ma5

>import event.lhe.gz

>plot PT(h1) 100 0 400 [logY]

>submit

then I get the PT(h1) before shower. To get the transverse momentum of higgs after shower, I type

>ma5

>import events_

>plot PT(h1) 100 0 400 [logY interstate]

>plot PT(h1[1]) 100 0 400 [logY interstate]

>submit

So I want to know which step is wrong, and which differential distribution after shower ( PT(h1) or PT(h1[1]) ) is correct to compare with the distribution before shower.

Thank you very much!

Sincerely yours,

Huanyu Bi

At2018-12-22 04:03:05,Olivier Mattelaer<email address hidden>wrote:

> Your question #676961 on MadGraph5_aMC@NLO changed:

> https:/

>

> Status: Open => Answered

>

> Olivier Mattelaer proposed the following answer:

> >From the information that I see in your mail.

> I would say that one correct option is to keep ickkw=0

> and the two others parameter are then fine as well.

>

> Now I do not know how you will handle those samples. If you want to merge those with other samples generated with

> p p > z z h j [QCD]

> Then obviously the above choice is not appropriate.

>

> Cheers,

>

> Olivier

>

> --

> If this answers your question, please go to the following page to let us

> know that it is solved:

> https:/

>

> If you still need help, you can reply to this email or go to the

> following page to enter your feedback:

> https:/

>

> You received this question notification because you asked the question.

Hi,

Distribution "before PS" in NLO+PS are not physical and therefore should be used with caution.

So the typical comparison is between NLO+PS (with MC@NLO formalism) compare to fix-order NLO.

(which is not the same as "before PS" due to the MC@NLO substraction scheme removing double counting)

> The question is that the two distributions after shower, i.e., PT(h1) and PT(h1[1]), are different in shape，

This you should ask the MG5aMC author. This means that you have more than one Higgs plotted in your sample.

> and the integral cross section of PT(h1) after shower is much bigger than that of PT(h1) before shower and that of PT(h1[1]) after shower, i.e., sigma(PT(

This is just because you have more than one Higgs entering the plot per-events.

Cheers,

Olivier

> On 22 Dec 2018, at 10:27, HuanyuBi <email address hidden> wrote:

>

> Question #676961 on MadGraph5_aMC@NLO changed:

> https:/

>

> Status: Answered => Open

>

> HuanyuBi is still having a problem:

> Dear Olivier,

> Thank you for your answer. I don't plan to merge pp>zzh [QCD] with pp>zzhj. I have another problem.

> I want to compare some differential distribution, e.g, the transverse momentum of higgs (PT(h1)) before and after parton shower. I use ma5

>> ma5

>> import event.lhe.gz

>> plot PT(h1) 100 0 400 [logY]

>> submit

> then I get the PT(h1) before shower. To get the transverse momentum of higgs after shower, I type

>> ma5

>> import events_

>> plot PT(h1) 100 0 400 [logY interstate]

>> plot PT(h1[1]) 100 0 400 [logY interstate]

>> submit

> The question is that the two distributions after shower, i.e., PT(h1) and PT(h1[1]), are different in shape， and the integral cross section of PT(h1) after shower is much bigger than that of PT(h1) before shower and that of PT(h1[1]) after shower, i.e., sigma(PT(

> So I want to know which step is wrong, and which differential distribution after shower ( PT(h1) or PT(h1[1]) ) is correct to compare with the distribution before shower.

>

> Thank you very much!

>

> Sincerely yours,

>

> Huanyu Bi

>

> At2018-12-22 04:03:05,Olivier Mattelaer<email address hidden>wrote:

>> Your question #676961 on MadGraph5_aMC@NLO changed:

>> https:/

>>

>> Status: Open => Answered

>>

>> Olivier Mattelaer proposed the following answer:

>>> From the information that I see in your mail.

>> I would say that one correct option is to keep ickkw=0

>> and the two others parameter are then fine as well.

>>

>> Now I do not know how you will handle those samples. If you want to merge those with other samples generated with

>> p p > z z h j [QCD]

>> Then obviously the above choice is not appropriate.

>>

>> Cheers,

>>

>> Olivier

>>

>> --

>> If this answers your question, please go to the following page to let us

>> know that it is solved:

>> https:/

>>

>> If you still need help, you can reply to this email or go to the

>> following page to enter your feedback:

>> https:/

>>

>> You received this question notification because you asked the question.

>

> --

> You received this question notification because you are an answer

> contact for MadGraph5_aMC@NLO.

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