negative decay width in loop induced higgs decay.

Asked by Md.Raju on 2019-04-29

Dear MG5 Developers
I have build a effective model for higgs decay to gluon and photon with full loop function and also explicit real value of 4mt^2/mh^2 with if condition in feynrule.Every thing is going ok but when I scan the higgs mass to 600 gev or higher value with Auto command to the higgs width the madgraph showing a error that h > g g partial decay width negative and stopped .I am not able to understand where lies the problem.

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Last query:
2019-05-01
Last reply:
2019-05-01

Do you have a file decays.py in your UFO model?

If you do not, the auto command, should use madevent where I have hard-time to see how a negative result can be generated.
On the other-hand if that file exists, then the partial-width is evaluated according to that file (which is coming from an analytical computation in FeynRules). There I can imagine how a negative number can arise.

Can you check that such formula makes sense?
and then look from which term such negative component is coming?

Cheers,

Olivier

Md.Raju (rahi199065) said : #2

Sir,I am very thankful for your kind response
from your question answer session I have solved that problem I have deleted
the decay.py file and there is no negative partial decay width.Is it ok?
Now I want to know few more things ..
1.I have build a model 2HDMTII with haa and hgg coupling to get g g > h
*br(h > tau tau) but when I set the Auto mode I got crossection and decay
width in one file and branching ratio in each scan file...I don’t
understand the out put file or how can get cross section and branching
ratio in one number.

On Tue, Apr 30, 2019 at 1:27 AM Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Do you have a file decays.py in your UFO model?
>
> If you do not, the auto command, should use madevent where I have
> hard-time to see how a negative result can be generated.
> On the other-hand if that file exists, then the partial-width is evaluated
> according to that file (which is coming from an analytical computation in
> FeynRules). There I can imagine how a negative number can arise.
>
> Can you check that such formula makes sense?
> and then look from which term such negative component is coming?
>
> Cheers,
>
> Olivier
>
> --
> 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/680525/+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/680525
>
> You received this question notification because you asked the question.
>

Hi,

>from your question answer session I have solved that problem I have deleted
the decay.py file and there is no negative partial decay width.Is it ok?

It means that you have a bug at the FeynRules level. If you do not understand what's going on at FeynRules level this sounds worrisome but this is your call to made not mine.

For your question, could you give more details, I'm not sure what your issue is.
Do I understand correctly that you want the cross-section for g g >h, h > ta+ ta-
after that what is your issue?

Cheers,

Olivier

Md.Raju (rahi199065) said : #4

 1.The bug is at feynrule level but madgraph calculate the decay width
correctly and my result for haa and hgg exactly matched with the inbuild
model heft.Does it necessary to understand the bug at feynrule level .
2.I want to generate cross section times branching ratio in one result file.
3.I am not understanding what is the role of auto command?

On Tue, Apr 30, 2019 at 11:57 PM Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> >from your question answer session I have solved that problem I have
> deleted
> the decay.py file and there is no negative partial decay width.Is it ok?
>
> It means that you have a bug at the FeynRules level. If you do not
> understand what's going on at FeynRules level this sounds worrisome but
> this is your call to made not mine.
>
> For your question, could you give more details, I'm not sure what your
> issue is.
> Do I understand correctly that you want the cross-section for g g >h, h >
> ta+ ta-
> after that what is your issue?
>
> Cheers,
>
> Olivier
>
> --
> 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/680525/+confirm?answer_id=2
>
> 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/680525
>
> You received this question notification because you asked the question.
>

Md.Raju (rahi199065) said : #5

I attaching the event file the branching ratio and partial decay width
showing here is it physical ?

On Wed, May 1, 2019 at 9:31 AM md raju <email address hidden> wrote:

> 1.The bug is at feynrule level but madgraph calculate the decay width
> correctly and my result for haa and hgg exactly matched with the inbuild
> model heft.Does it necessary to understand the bug at feynrule level .
> 2.I want to generate cross section times branching ratio in one result
> file.
> 3.I am not understanding what is the role of auto command?
>
>
> On Tue, Apr 30, 2019 at 11:57 PM Olivier Mattelaer <
> <email address hidden>> wrote:
>
>> Your question #680525 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/680525
>>
>> Status: Open => Answered
>>
>> Olivier Mattelaer proposed the following answer:
>> Hi,
>>
>> >from your question answer session I have solved that problem I have
>> deleted
>> the decay.py file and there is no negative partial decay width.Is it ok?
>>
>> It means that you have a bug at the FeynRules level. If you do not
>> understand what's going on at FeynRules level this sounds worrisome but
>> this is your call to made not mine.
>>
>> For your question, could you give more details, I'm not sure what your
>> issue is.
>> Do I understand correctly that you want the cross-section for g g >h, h >
>> ta+ ta-
>> after that what is your issue?
>>
>> Cheers,
>>
>> Olivier
>>
>> --
>> 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/680525/+confirm?answer_id=2
>>
>> 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/680525
>>
>> You received this question notification because you asked the question.
>>
>

where did you put the attachment?
You forget to put the link to the website where you upload your file.

1.The bug is at feynrule level but madgraph calculate the decay width
correctly and my result for haa and hgg exactly matched with the inbuild
model heft.Does it necessary to understand the bug at feynrule level .

I would not trust your model without understanding what is the problem at FR level.
But this is your call not mine

2.I want to generate cross section times branching ratio in one result file.

So yes the above syntax should give you that.

3.I am not understanding what is the role of auto command?

THe auto command allows to compute automatically the total width.
(MG5aMC does not use the branching ratio, so it needs to know the total width for computing your cross-section. Since the width is not a free parameter we provide the auto mode for that.
Please read the associate paper:arXiv:1402.1178<http://arXiv.org/abs/arXiv:1402.1178>

Cheers,

Olivier

On 1 May 2019, at 06:12, Md.Raju <<email address hidden><mailto:<email address hidden>>> wrote:

Question #680525 on MadGraph5_aMC@NLO changed:
https://answers.launchpad.net/mg5amcnlo/+question/680525

Md.Raju gave more information on the question:
I attaching the event file the branching ratio and partial decay width
showing here is it physical ?

On Wed, May 1, 2019 at 9:31 AM md raju <email address hidden> wrote:

1.The bug is at feynrule level but madgraph calculate the decay width
correctly and my result for haa and hgg exactly matched with the inbuild
model heft.Does it necessary to understand the bug at feynrule level .
2.I want to generate cross section times branching ratio in one result
file.
3.I am not understanding what is the role of auto command?

On Tue, Apr 30, 2019 at 11:57 PM Olivier Mattelaer <
<email address hidden>> wrote:

Your question #680525 on MadGraph5_aMC@NLO changed:
https://answers.launchpad.net/mg5amcnlo/+question/680525

   Status: Open => Answered

Olivier Mattelaer proposed the following answer:
Hi,

from your question answer session I have solved that problem I have
deleted
the decay.py file and there is no negative partial decay width.Is it ok?

It means that you have a bug at the FeynRules level. If you do not
understand what's going on at FeynRules level this sounds worrisome but
this is your call to made not mine.

For your question, could you give more details, I'm not sure what your
issue is.
Do I understand correctly that you want the cross-section for g g >h, h >
ta+ ta-
after that what is your issue?

Cheers,

Olivier

--
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/680525/+confirm?answer_id=2

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/680525

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.

Md.Raju (rahi199065) said : #7

Thank you for your patient answer of my question.
But feynrule not showing any error so what is the reason of generation of
decay.py in madgraph how can I detect the bug in feynrule because the
origin of problem is decay .py

On Wed, May 1, 2019 at 11:57 AM Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> where did you put the attachment?
> You forget to put the link to the website where you upload your file.
>
> 1.The bug is at feynrule level but madgraph calculate the decay width
> correctly and my result for haa and hgg exactly matched with the inbuild
> model heft.Does it necessary to understand the bug at feynrule level .
>
> I would not trust your model without understanding what is the problem at
> FR level.
> But this is your call not mine
>
> 2.I want to generate cross section times branching ratio in one result
> file.
>
> So yes the above syntax should give you that.
>
> 3.I am not understanding what is the role of auto command?
>
> THe auto command allows to compute automatically the total width.
> (MG5aMC does not use the branching ratio, so it needs to know the total
> width for computing your cross-section. Since the width is not a free
> parameter we provide the auto mode for that.
> Please read the associate paper:arXiv:1402.1178<
> http://arXiv.org/abs/arXiv:1402.1178>
>
> Cheers,
>
> Olivier
>
> On 1 May 2019, at 06:12, Md.Raju
> <<email address hidden><mailto:
> <email address hidden>>>
> wrote:
>
> Question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Md.Raju gave more information on the question:
> I attaching the event file the branching ratio and partial decay width
> showing here is it physical ?
>
> On Wed, May 1, 2019 at 9:31 AM md raju <email address hidden> wrote:
>
> 1.The bug is at feynrule level but madgraph calculate the decay width
> correctly and my result for haa and hgg exactly matched with the inbuild
> model heft.Does it necessary to understand the bug at feynrule level .
> 2.I want to generate cross section times branching ratio in one result
> file.
> 3.I am not understanding what is the role of auto command?
>
>
> On Tue, Apr 30, 2019 at 11:57 PM Olivier Mattelaer <
> <email address hidden>> wrote:
>
> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> from your question answer session I have solved that problem I have
> deleted
> the decay.py file and there is no negative partial decay width.Is it ok?
>
> It means that you have a bug at the FeynRules level. If you do not
> understand what's going on at FeynRules level this sounds worrisome but
> this is your call to made not mine.
>
> For your question, could you give more details, I'm not sure what your
> issue is.
> Do I understand correctly that you want the cross-section for g g >h, h >
> ta+ ta-
> after that what is your issue?
>
> Cheers,
>
> Olivier
>
> --
> 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/680525/+confirm?answer_id=2
>
> 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/680525
>
> 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.
>
> --
> 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/680525/+confirm?answer_id=5
>
> 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/680525
>
> You received this question notification because you asked the question.
>

Decay.py is a file generated by feynrules at the same times as your model. An error in that file is likely to be correlated to an error in either Lorentz.py or couplings.py.

My suggestion would be to look at the expression within decay.py and understand why the width is negative and then discuss this with Benjamin fuks

Cheers

Olivier

Get Outlook for iOS<https://aka.ms/o0ukef>

________________________________
From: <email address hidden> on behalf of Md.Raju <email address hidden>
Sent: Wednesday, May 1, 2019 6:09 PM
To: Olivier Mattelaer
Subject: Re: [Question #680525]: negative decay width in loop induced higgs decay.

Question #680525 on MadGraph5_aMC@NLO changed:
https://answers.launchpad.net/mg5amcnlo/+question/680525

Status: Answered => Open

Md.Raju is still having a problem:
Thank you for your patient answer of my question.
But feynrule not showing any error so what is the reason of generation of
decay.py in madgraph how can I detect the bug in feynrule because the
origin of problem is decay .py

On Wed, May 1, 2019 at 11:57 AM Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> where did you put the attachment?
> You forget to put the link to the website where you upload your file.
>
> 1.The bug is at feynrule level but madgraph calculate the decay width
> correctly and my result for haa and hgg exactly matched with the inbuild
> model heft.Does it necessary to understand the bug at feynrule level .
>
> I would not trust your model without understanding what is the problem at
> FR level.
> But this is your call not mine
>
> 2.I want to generate cross section times branching ratio in one result
> file.
>
> So yes the above syntax should give you that.
>
> 3.I am not understanding what is the role of auto command?
>
> THe auto command allows to compute automatically the total width.
> (MG5aMC does not use the branching ratio, so it needs to know the total
> width for computing your cross-section. Since the width is not a free
> parameter we provide the auto mode for that.
> Please read the associate paper:arXiv:1402.1178<
> http://arXiv.org/abs/arXiv:1402.1178>
>
> Cheers,
>
> Olivier
>
> On 1 May 2019, at 06:12, Md.Raju
> <<email address hidden><mailto:
> <email address hidden>>>
> wrote:
>
> Question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Md.Raju gave more information on the question:
> I attaching the event file the branching ratio and partial decay width
> showing here is it physical ?
>
> On Wed, May 1, 2019 at 9:31 AM md raju <email address hidden> wrote:
>
> 1.The bug is at feynrule level but madgraph calculate the decay width
> correctly and my result for haa and hgg exactly matched with the inbuild
> model heft.Does it necessary to understand the bug at feynrule level .
> 2.I want to generate cross section times branching ratio in one result
> file.
> 3.I am not understanding what is the role of auto command?
>
>
> On Tue, Apr 30, 2019 at 11:57 PM Olivier Mattelaer <
> <email address hidden>> wrote:
>
> Your question #680525 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/680525
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> from your question answer session I have solved that problem I have
> deleted
> the decay.py file and there is no negative partial decay width.Is it ok?
>
> It means that you have a bug at the FeynRules level. If you do not
> understand what's going on at FeynRules level this sounds worrisome but
> this is your call to made not mine.
>
> For your question, could you give more details, I'm not sure what your
> issue is.
> Do I understand correctly that you want the cross-section for g g >h, h >
> ta+ ta-
> after that what is your issue?
>
> Cheers,
>
> Olivier
>
> --
> 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/680525/+confirm?answer_id=2
>
> 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/680525
>
> 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.
>
> --
> 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/680525/+confirm?answer_id=5
>
> 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/680525
>
> You received this question notification because you asked the question.
>

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