On shell production and decay cross section

Branching ratio are not used by madgraph.
our cross-section is proportional to the coupling and the width.
The Branching ratio do not enter the computation at any point

Cheers,

Olivier
> On Jan 27, 2016, at 21:07, alberto <email address hidden> wrote:
>
> New question #283805 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/283805
>
> I have a model with some state H5pp and I run
>
> generate p p > H5pp j j
>
> and I get some value for the xsection, call it sigma0.
>
> Then I do
>
> generate p p > H5pp j j, H5pp > w+ w+.
>
> Before running I usually modify the file param_card.dat.
>
> For the parameter values I choose, the branching ratio (BR) H5pp> w+ w+ is 1. (H5pp has also a narrow width)
>
> I would expect for the latter process to obtain a sigma = sigma0*BR = sigma0. (since
> BR=1).
>
> But I get a different result, which is 10^-2 smaller.
>
> What am I missing?
>
> Thanks.
>
> Alberto
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Maybe I have undestand what I am missing.

In the param_card.dat the width of the particle H5pp has some default value that does not change when I modify the external parameters.

If I have undertstood correctly , I have to set the flag AUTO in the

###################################
## INFORMATION FOR DECAY
###################################
DECAY xx AUTO # H5pp

but I get this error (I am using MG5_v2.3.3)

Command "generate_events run_02" interrupted in sub-command:
"set max_npoint_for_channel 0" with error:
NameError : name 'Abot' is not defined
Please report this bug on https://bugs.launchpad.net/madgraph5
More information is found in 'MG5_debug'.
Please attach this file to your report.

Thanks.

Cheers,

Alberto

Hi,

Hi,

I do not find any string matching “Abot” in our code.
I guess that this is a problem of your model.

Could you check if “Abot” is somewhere in your model and it it is that it is correctly define.

Cheers,

Olivier

> On Jan 28, 2016, at 17:37, alberto <email address hidden> wrote:
>
> Question #283805 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/283805
>
> Status: Answered => Open
>
> alberto is still having a problem:
> Maybe I have undestand what I am missing.
>
> In the param_card.dat the width of the particle H5pp has some default
> value that does not change when I modify the external parameters.
>
> If I have undertstood correctly , I have to set the flag AUTO in the
>
> ###################################
> ## INFORMATION FOR DECAY
> ###################################
> DECAY xx AUTO # H5pp
>
> but I get this error (I am using MG5_v2.3.3)
>
> Command "generate_events run_02" interrupted in sub-command:
> "set max_npoint_for_channel 0" with error:
> NameError : name 'Abot' is not defined
> Please report this bug on https://bugs.launchpad.net/madgraph5
> More information is found in 'MG5_debug'.
> Please attach this file to your report.
>
> Thanks.
>
> Cheers,
>
> Alberto
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

sorry, maybe I was too quick. Let me try to add more details.

"Abot" is a function that I have added in the file functions.f in the folder Fortran in the UFO.

This function is used il lorentz.py to define a new vertex.

The file decays.py has no information about "Abot".

Thanks.

Cheers,

Alberto

Hi,

What you can try is to remove the file decays.py.
This will force the code to do the computation of the two body decay in Fortran where you function will be define (at least I hope).

Cheers,

Olivier