HEFT with gg>e+e-mu+mu- /A VERSUS gg>ZZ , Z>e+e- , Z>mu+mu-

Hi,

The second syntax forces the two Z to be on shell which is not the case of your first syntax.

Cheers,

Olivier

PS: The first syntax also includes diagram with two photons and report two diagrams and not one.

On 12 Aug 2015, at 10:26, Andre Sznajder <email address hidden> wrote:

> New question #270267 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/270267
>
> I am comparing two gluon fusion Higgs production processes and I don't understand why I very different results. I am using the HEFT model for both processes bellow:
>
> 1) g g > e+ e- mu+ mu-
> 2) g g > Z Z , Z > e+ e- , Z > mu+ mu-
>
> They both give one single diagram ( gluon fusion Higgs production with decay into ZZ followed by Z decays ) according to Madgraph and when I plot the Pt distributions for the leptons I get a completely different result !
> The first , which is the complete process gives a monotonically decreasing Pt distribution with a peak around 45GeV , which I think is reasonable because the diagram has a resonating Z which decays into a pair of massless leptons .
> On the other hand the decay chain process which has Z's on shell that are smeared by a Breit-Wigner gives a lepton Pt distribution which is monotonically decreasing without any peaks.
> If I plot the 4 body mass they both show a peak at the Higgs mass and an almost flat continuum after 180GeV , but the ratio of the Higgs peak maximum over the continuum maximum for the full process is two orders of magnitude higher than the decay chain.
> Why should there be such difference ?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
Ok, I forgot to copy in the previous message the /A ( but it is in the message subject... ) . I am using /A when generating the first process, so do I have only one diagram.
I know the second forces the two Zs to be on shell and that’w why it strikes me not to see the peak at 45GeV !
Also, why do I get such difference ( 2 orders of magnitude ) in the ratio between Higgs on shell versus offshell when I plot the 4 lepton mass ?
Thanks,
Andre

> On Aug 12, 2015, at 11:41 AM, Olivier Mattelaer <email address hidden> wrote:
>
> Your question #270267 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/270267
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> The second syntax forces the two Z to be on shell which is not the case
> of your first syntax.
>
> Cheers,
>
> Olivier
>
> PS: The first syntax also includes diagram with two photons and report
> two diagrams and not one.
>
>
> On 12 Aug 2015, at 10:26, Andre Sznajder <email address hidden> wrote:
>
>> New question #270267 on MadGraph5_aMC@NLO:
>> https://answers.launchpad.net/mg5amcnlo/+question/270267
>>
>> I am comparing two gluon fusion Higgs production processes and I don't understand why I very different results. I am using the HEFT model for both processes bellow:
>>
>> 1) g g > e+ e- mu+ mu-
>> 2) g g > Z Z , Z > e+ e- , Z > mu+ mu-
>>
>> They both give one single diagram ( gluon fusion Higgs production with decay into ZZ followed by Z decays ) according to Madgraph and when I plot the Pt distributions for the leptons I get a completely different result !
>> The first , which is the complete process gives a monotonically decreasing Pt distribution with a peak around 45GeV , which I think is reasonable because the diagram has a resonating Z which decays into a pair of massless leptons .
>> On the other hand the decay chain process which has Z's on shell that are smeared by a Breit-Wigner gives a lepton Pt distribution which is monotonically decreasing without any peaks.
>> If I plot the 4 body mass they both show a peak at the Higgs mass and an almost flat continuum after 180GeV , but the ratio of the Higgs peak maximum over the continuum maximum for the full process is two orders of magnitude higher than the decay chain.
>> Why should there be such difference ?
>>
>> --
>> You received this question notification because you are an answer
>> contact for MadGraph5_aMC@NLO.
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
> https://answers.launchpad.net/mg5amcnlo/+question/270267/+confirm?answer_id=0
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
> https://answers.launchpad.net/mg5amcnlo/+question/270267
>
> You received this question notification because you asked the question.

===================================================
Andre Sznajder
Professor Associado
Instituto de Fisica - Dept. DFNAE
Universidade do Estado do Rio de Janeiro ( UERJ )
Rio de Janeiro, RJ - Brasil
Tel.: (+55)(21)23340608 ramal:24 Fax: (+55)(21)23340483
Email: <email address hidden>
===================================================

> Also, why do I get such difference ( 2 orders of magnitude ) in the ratio between Higgs on shell versus off shell when I plot the 4 lepton mass ?

The bulk of the cross-section is when you have the Higgs on shell and one Z.
A second important contribution comes for the the Higgs off-shell and the two Z on shell.
With the second syntax, you keep the second contribution but completely kill your first one.
(Not completely but the only contribution you keep is border off the Z on shell for both Z which means Z at 60 GeV)
Due to that, you have a lot bullshit.

Cheers,

Olivier

On 12 Aug 2015, at 10:51, Andre Sznajder <email address hidden> wrote:

> Question #270267 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/270267
>
> Status: Answered => Open
>
> Andre Sznajder is still having a problem:
> Hi Olivier,
> Ok, I forgot to copy in the previous message the /A ( but it is in the message subject... ) . I am using /A when generating the first process, so do I have only one diagram.
> I know the second forces the two Zs to be on shell and that’w why it strikes me not to see the peak at 45GeV !
> Also, why do I get such difference ( 2 orders of magnitude ) in the ratio between Higgs on shell versus offshell when I plot the 4 lepton mass ?
> Thanks,
> Andre
>
>> On Aug 12, 2015, at 11:41 AM, Olivier Mattelaer <email address hidden> wrote:
>>
>> Your question #270267 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/270267
>>
>> Status: Open => Answered
>>
>> Olivier Mattelaer proposed the following answer:
>> Hi,
>>
>> The second syntax forces the two Z to be on shell which is not the case
>> of your first syntax.
>>
>> Cheers,
>>
>> Olivier
>>
>> PS: The first syntax also includes diagram with two photons and report
>> two diagrams and not one.
>>
>>
>> On 12 Aug 2015, at 10:26, Andre Sznajder <email address hidden> wrote:
>>
>>> New question #270267 on MadGraph5_aMC@NLO:
>>> https://answers.launchpad.net/mg5amcnlo/+question/270267
>>>
>>> I am comparing two gluon fusion Higgs production processes and I don't understand why I very different results. I am using the HEFT model for both processes bellow:
>>>
>>> 1) g g > e+ e- mu+ mu-
>>> 2) g g > Z Z , Z > e+ e- , Z > mu+ mu-
>>>
>>> They both give one single diagram ( gluon fusion Higgs production with decay into ZZ followed by Z decays ) according to Madgraph and when I plot the Pt distributions for the leptons I get a completely different result !
>>> The first , which is the complete process gives a monotonically decreasing Pt distribution with a peak around 45GeV , which I think is reasonable because the diagram has a resonating Z which decays into a pair of massless leptons .
>>> On the other hand the decay chain process which has Z's on shell that are smeared by a Breit-Wigner gives a lepton Pt distribution which is monotonically decreasing without any peaks.
>>> If I plot the 4 body mass they both show a peak at the Higgs mass and an almost flat continuum after 180GeV , but the ratio of the Higgs peak maximum over the continuum maximum for the full process is two orders of magnitude higher than the decay chain.
>>> Why should there be such difference ?
>>>
>>> --
>>> You received this question notification because you are an answer
>>> contact for MadGraph5_aMC@NLO.
>>
>> --
>> If this answers your question, please go to the following page to let us
>> know that it is solved:
>> https://answers.launchpad.net/mg5amcnlo/+question/270267/+confirm?answer_id=0
>>
>> If you still need help, you can reply to this email or go to the
>> following page to enter your feedback:
>> https://answers.launchpad.net/mg5amcnlo/+question/270267
>>
>> You received this question notification because you asked the question.
>
> ===================================================
> Andre Sznajder
> Professor Associado
> Instituto de Fisica - Dept. DFNAE
> Universidade do Estado do Rio de Janeiro ( UERJ )
> Rio de Janeiro, RJ - Brasil
> Tel.: (+55)(21)23340608 ramal:24 Fax: (+55)(21)23340483
> Email: <email address hidden>
> ===================================================
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.