Hi Olivier,

I am trying to generate events for process gg > h2 > h3 z* > h1 z* z* > bb jj mu+mu-, with h1 > b b~, h2 is. SM-like and mh1, mh3 < mh2 (2hdm type-1). I am using madgraph to compute the cross-section of this process.
PS: z's are off-shell.

I am confused because of the difference in the cross section due to the syntax:

part 1:
gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j)
cross section = 3.57x10^-4 pb

part 2 :
gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j, h1 > b b~)
cross section = 0.48pb

The first value seems more reasonable since h2 is SM-like. What do you think is the reason behind the huge difference?

I tried to compute the cross-section using madgraph (gg > h2) and madspin (for the rest of the process), but then I am getting different values for different syntax (FAQ):

#=============
#============

case1:
# specify the decay for the final state particles
decay h2 > z > h3 mu+ mu-, h3 > z > h1 j j, h1 > b b~
sigma = 6.7x10^-4pb

case 2
# specify the decay for the final state particles
decay h2 > z > h3 mu+ mu-, (h3 > z > h1 j j, h1 > b b~)
sigama = 0.54pb

Many thanks for any suggestion or explanation to alleviate the confusion.

Best regards

## Question information

Language:
English Edit question
Status:
For:
Assignee:
No assignee Edit question
Last query:
 Revision history for this message Olivier Mattelaer (olivier-mattelaer) said on 2021-07-06: #1

Hi,

For the first missmatch:

> part 1:
> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j)
> cross section = 3.57x10^-4 pb
>
> part 2 :
> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j, h1 > b b~)
> cross section = 0.48pb

This typically means that the total width of h1 is not set to the correct value for your computation.

The first syntax is simply wrong since you ask the h1 comming from "h2 > z > h3 mu+ mu-" to decay. But since that process does not have any h1, your syntax is the same as
decay h2 > z > h3 mu+ mu-, h3 > z > h1 j j

Now if h2 can be consider/assume as onshell (and in the narrow-width approximation)
then you should use
generate g g > h2 , ( h2 > h3 mu+ mu-, ( h3 > z > h1 j j , h1 > b b~)
(which also assume NWA for h3 and h1)

or if the following is gauge invariant you can also use
generate g g > h2 , ( h2 > z > h3 mu+ mu-, ( h3 > z > h1 j j , h1 > b b~)

Cheers,

Olivier
> On 6 Jul 2021, at 03:41, SOUAD SEMLALI <email address hidden> wrote:
>
> New question #697866 on MadGraph5_aMC@NLO:
>
> Hi Olivier,
>
> I am trying to generate events for process gg > h2 > h3 z* > h1 z* z* > bb jj mu+mu-, with h1 > b b~, h2 is. SM-like and mh1, mh3 < mh2 (2hdm type-1). I am using madgraph to compute the cross-section of this process.
> PS: z's are off-shell.
>
> I am confused because of the difference in the cross section due to the syntax:
>
> part 1:
> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j)
> cross section = 3.57x10^-4 pb
>
> part 2 :
> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j, h1 > b b~)
> cross section = 0.48pb
>
> The first value seems more reasonable since h2 is SM-like. What do you think is the reason behind the huge difference?
>
> I tried to compute the cross-section using madgraph (gg > h2) and madspin (for the rest of the process), but then I am getting different values for different syntax (FAQ):
>
> #=============
> #============
>
> case1:
> # specify the decay for the final state particles
> decay h2 > z > h3 mu+ mu-, h3 > z > h1 j j, h1 > b b~
> sigma = 6.7x10^-4pb
>
> case 2
> # specify the decay for the final state particles
> decay h2 > z > h3 mu+ mu-, (h3 > z > h1 j j, h1 > b b~)
> sigama = 0.54pb
>
> Many thanks for any suggestion or explanation to alleviate the confusion.
>
> Best regards
>
>
>
>
>
> --

 Revision history for this message SOUAD SEMLALI (souad-sem) said on 2021-07-06: #2

Hi Olivier,

Many thanks for your email.. I am afraid, I still need your help.

> Le 6 juil. 2021 à 19:41, Olivier Mattelaer <email address hidden> a écrit :
>
>
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> For the first missmatch:
>
>> part 1:
>> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j)
>> cross section = 3.57x10^-4 pb
>>
>> part 2 :
>> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j, h1 > b b~)
>> cross section = 0.48pb
>
> This typically means that the total width of h1 is not set to the
> correct value for your computation.

I have already included the total width of h1 (4.68e-9) in the parameter card, as well as the branching ratio of Br(h1 -> bb) ~ 70%. How can we set then the total width to the correct value?
>
>
> The first syntax is simply wrong since you ask the h1 comming from "h2 > z > h3 mu+ mu-" to decay. But since that process does not have any h1, your syntax is the same as
> decay h2 > z > h3 mu+ mu-, h3 > z > h1 j j
I understand now, thanks!
>
> Now if h2 can be consider/assume as onshell (and in the narrow-width approximation)
> then you should use
> generate g g > h2 , ( h2 > h3 mu+ mu-, ( h3 > z > h1 j j , h1 > b b~)
> (which also assume NWA for h3 and h1)
h1, h2 and h3 are on-shell, and I guess we can assume the NWA, total width\ mX of each scalar < 1%, with mX= mh, mH, mA.
>
> or if the following is gauge invariant you can also use
> generate g g > h2 , ( h2 > z > h3 mu+ mu-, ( h3 > z > h1 j j , h1 > b b~)

This process g g > h2 z > mu+ mu- passed Lorentz invariance but failed gauge check.
Gauge results (switching between Unitary/Feynman/axial gauge):
Process Unitary Feynman Relative diff. Result
g g > h3 mu+ mu- 2.7527784365e-10 2.7527796585e-10 4.4393101950e-07 Failed
JAMP 0 3.5235563987e-08 3.5235579629e-08 4.4393101969e-07 Failed
Summary: 0/1 passed, 1/1 failed
Failed processes: g g > h3 mu+ mu-

What do you think? I am interested in the diagrams where z decaying into mu+ mu-.

Best regards

>
> Cheers,
>
> Olivier
>> On 6 Jul 2021, at 03:41, SOUAD SEMLALI <email address hidden> wrote:
>>
>> New question #697866 on MadGraph5_aMC@NLO:
>>
>> Hi Olivier,
>>
>> I am trying to generate events for process gg > h2 > h3 z* > h1 z* z* > bb jj mu+mu-, with h1 > b b~, h2 is. SM-like and mh1, mh3 < mh2 (2hdm type-1). I am using madgraph to compute the cross-section of this process.
>> PS: z's are off-shell.
>>
>> I am confused because of the difference in the cross section due to the syntax:
>>
>> part 1:
>> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j)
>> cross section = 3.57x10^-4 pb
>>
>> part 2 :
>> gg> h2 z > h3 mu+ mu-, ( h3 > z > h1 j j, h1 > b b~)
>> cross section = 0.48pb
>>
>> The first value seems more reasonable since h2 is SM-like. What do you think is the reason behind the huge difference?
>>
>> I tried to compute the cross-section using madgraph (gg > h2) and madspin (for the rest of the process), but then I am getting different values for different syntax (FAQ):
>>
>> #=============
>> #============
>>
>> case1:
>> # specify the decay for the final state particles
>> decay h2 > z > h3 mu+ mu-, h3 > z > h1 j j, h1 > b b~
>> sigma = 6.7x10^-4pb
>>
>> case 2
>> # specify the decay for the final state particles
>> decay h2 > z > h3 mu+ mu-, (h3 > z > h1 j j, h1 > b b~)
>> sigama = 0.54pb
>>
>> Many thanks for any suggestion or explanation to alleviate the confusion.
>>
>> Best regards
>>
>>
>>
>>
>>
>> --
>
> --
> know that it is solved:
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
>

 Revision history for this message Olivier Mattelaer (olivier-mattelaer) said on 2021-07-10: #3

If you set the width to auto for h1.
How much that width is computed?
the auto-width ignores loop-induced decay and can under-estimate the total width, but this will provides a good indication if your width is not set too small.

Cheers,

Olivier

 Revision history for this message SOUAD SEMLALI (souad-sem) said on 2021-07-13: #4

Dear Olivier,

Thanks a lot for your help all this time!

I have indeed set the width to auto for h1. But, I get this error message:

INFO: failed to load model from pickle file. Try importing UFO from File
INFO: Change particles name to pass to MG5 convention
INFO: syntax: compute_widths Particle [Particles] [OPTIONS]
INFO: -- Compute the widths for the particles specified.
INFO: By default, this takes the current param_card and overwrites it.
INFO: Precision allows to define when to include three/four/... body decays (LO).
INFO: If this number is an integer then all N-body decay will be included.
INFO: Various options:

INFO: --body_decay=X: Parameter to control the precision of the computation
INFO: if X is an integer, we compute all channels up to X-body decay.
INFO: if X <1, then we stop when the estimated error is lower than X.
INFO: if X >1 BUT not an integer, then we X = N + M, with M <1 and N an integer
INFO: We then either stop at the N-body decay or when the estimated error is lower than M.
INFO: default: 4.0025
INFO: --min_br=X: All channel which are estimated below this value will not be integrated numerically.
INFO: default: precision (decimal part of the body_decay options) divided by four
INFO: --precision_channel=X: requested numerical precision for each channel
INFO: default: 0.01
INFO: --path=X: path for param_card
INFO: default: take value from the model
INFO: --output=X: path where to write the resulting card.
INFO: default: overwrite input file. If no input file, write it in the model directory
INFO: --nlo: Compute NLO width [if the model support it]
ERROR: Invalid command: 25 is not a valid argument for compute_widths
INFO: Update the dependent parameter of the param_card.dat
Command "generate_events run_01" interrupted with error:
ValueError : invalid literal for int() with base 10: 'autoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoautoaut

I have checked this question to learn about the problem that rises after merging 2 models (https://answers.launchpad.net/mg5amcnlo/+question/687936))

You have mentioned (https://answers.launchpad.net/mg5amcnlo/+question/697452)) that the reason may be an issue with the plugin or the fact that the model is such that the computation of the width depends on the value of the width itself, leading to such an issue.

I did some checks:
- No problem after using the model file without hgg plugin and setting the width(s) to auto for h1 and/or h2 (good values)

No problem after using the model file with hgg plugin and setting the width to auto for h2 (good values)

Error message mentioned above, after using the model file with hgg plugin and setting the width to auto for h1.

Does this mean that there is a problem with the plugin?

Many thanks for any suggestion and help.

Best regards

 Revision history for this message Olivier Mattelaer (olivier-mattelaer) said on 2021-07-20: #5

Hi,

I do not know, I guess I would need to have the model (and maybe benchmark point as well) in order to investigate.
Since this is a question, you are not allowed to attach file (if you reply by email with attachment, the attachment will be automatically removed). The solution is either to convert this question to a bug report: https://answers.launchpad.net/mg5amcnlo/+question/697866/+makebug or to put the model somewhere accessible online.

Cheers,

Olivier