FCNC z-prime may not be working well since MadGraph5_v1_4_3?

Hi Ezequiel,

Could you send me your model (and the process that you check).
[olivier.mattelaer_AT_uclouvain.be]

I'm going to run this on my laptop to see what the problem is.

Cheers,

Olivier

On 15-mai-12, at 11:25, Ezequiel Alvarez wrote:

> New question #197342 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/197342
>
> Hello,
>
> Since version 5.1.4.3 I observe that when introducing a new model (à
> la v4) with FCNC Z', it does not work well. For instance, when the
> coupling is set to zero, gives a non-sense cross section in tt~
> production.
>
> These are my files (only relevant lines showing):
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> particles.dat:
> #MODEL EXTENSION
> zp zp V W zpm zpw S zp 2198
>
> interactions.dat:
> # USRVertex
> u t zp gzp QED
> t u zp gzp QED
>
> VariableName.dat:
> fr
>
> couplings.f:
> c************************************
> c UserMode couplings
> c************************************
>
> gzp(1)=dcmplx(1d0,Zero)
> gzp(2)=dcmplx(fr,Zero)
>
> That is for the model. Then, in the working directory:
>
> Cards/proc_card_mg5.dat:
> import model_v4 zprime
> ...
> generate p p > t t~ QED=2 @1
>
> Cards/param_card.dat:
> BLOCK MGUSER
> 1 0.00000000e+00 # fr,
>
> Cards/run_card.dat
> 4000 = ebeam1 ! beam 1 energy in GeV
> 4000 = ebeam2 ! beam 2 energy in GeV
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> So well, the issue comes when I run ./bin/generate_events since it
> gives me a cross section of 668 pb. (This is wrong, if the coupling
> fr=0 then it should be the SM cross-section that for these energies
> is ~130 pb.) Moreover, when I look the contributions to the 668 pb
> cross sections I see that the main contribution (515 pb) comes from
> the t-channel Z' FCNC, which should not be present, since the
> coupling fr is set to zero. However, if I set the Z' mass very
> large in param_card.dat, then yes it retrieves the SM cross section.
>
> I am confused: if the coupling fr is set to 0, it should retrieve
> the SM cross section, right?
>
> Thanks for your great software, and for your great availability
> here in launchpad,
>
> Ezequiel Alvarez.
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Hi Olivier,

I think I've found MY mistake. Don't spend your time running
anything, I'll update in a while my report. Thanks, Ezequiel.

On Tue, May 15, 2012 at 10:15 AM, Olivier Mattelaer
<email address hidden> wrote:
> Your question #197342 on MadGraph5 changed:
> https://answers.launchpad.net/madgraph5/+question/197342
>
>    Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi Ezequiel,
>
> Could you send me your model (and the process that you check).
> [olivier.mattelaer_AT_uclouvain.be]
>
> I'm going to run this on my laptop to see what the problem is.
>
> Cheers,
>
> Olivier
>
> On 15-mai-12, at 11:25, Ezequiel Alvarez wrote:
>
>> New question #197342 on MadGraph5:
>> https://answers.launchpad.net/madgraph5/+question/197342
>>
>> Hello,
>>
>> Since version 5.1.4.3 I observe that when introducing a new model (à
>> la v4) with FCNC Z', it does not work well.  For instance, when the
>> coupling is set to zero, gives a non-sense cross section in tt~
>> production.
>>
>> These are my files (only relevant lines showing):
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> particles.dat:
>> #MODEL EXTENSION
>> zp       zp       V        W      zpm    zpw     S   zp   2198
>>
>> interactions.dat:
>> #   USRVertex
>> u  t  zp  gzp  QED
>> t  u  zp  gzp  QED
>>
>> VariableName.dat:
>> fr
>>
>> couplings.f:
>> c************************************
>> c UserMode couplings
>> c************************************
>>
>>      gzp(1)=dcmplx(1d0,Zero)
>>      gzp(2)=dcmplx(fr,Zero)
>>
>> That is for the model.  Then, in the working directory:
>>
>> Cards/proc_card_mg5.dat:
>> import model_v4 zprime
>> ...
>> generate p p > t t~ QED=2 @1
>>
>> Cards/param_card.dat:
>> BLOCK MGUSER
>>         1     0.00000000e+00   # fr,
>>
>> Cards/run_card.dat
>>     4000     = ebeam1  ! beam 1 energy in GeV
>>     4000     = ebeam2  ! beam 2 energy in GeV
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> So well, the issue comes when I run ./bin/generate_events since it
>> gives me a cross section of 668 pb.  (This is wrong, if the coupling
>> fr=0 then it should be the SM cross-section that for these energies
>> is ~130 pb.) Moreover,  when I look the contributions to the 668 pb
>> cross sections I see that the main contribution (515 pb) comes from
>> the t-channel Z' FCNC, which should not be present, since the
>> coupling fr is set to zero.  However, if I set the Z' mass very
>> large in param_card.dat, then yes it retrieves the SM cross section.
>>
>> I am confused: if the coupling fr is set to 0, it should retrieve
>> the SM cross section, right?
>>
>> Thanks for your great software, and for your great  availability
>> here in launchpad,
>>
>> Ezequiel Alvarez.
>>
>> --
>> You received this question notification because you are a member of
>> MadTeam, which is an answer contact for MadGraph5.
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
> https://answers.launchpad.net/madgraph5/+question/197342/+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/madgraph5/+question/197342
>
> You received this question notification because you asked the question.

Hi Olivier,

I have found MY mistake: there was a "1d0" in the Left coupling in the couplings.f which I didn't set to Zero. I feel stupid.

Sorry about that, thanks again!

Bests,

Ezequiel.

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