Decay chain generation syntax

Asked by Igna on 2019-07-16

I'm looking into the decay chains whose Feynman diagrams I attached bellow. I would like to know if my generation syntax is correct (I'm a bit confused with the use of parenthesis). Where can I find the documentation about the generation syntax and MG?

generate e+ e- > ta+ ta- zp, zp > mu+ mu-, ta+ > mu+ vm vt~, ta- > mu- vt vm~ for https://drive.google.com/file/d/1Sf7CXLbcbibMJiQUVKBFt4JoN2rYkNWh/view?usp=sharing zmm

and

generate e+ e- > mu+ mu- zp, (zp > ta+ ta-, ta+ > mu+ vm vt~, ta- > mu- vt vm~) for

https://drive.google.com/file/d/1AcP0qQjzUOLAQgezoBU0zLWCDwGQRxr0/view?usp=sharing ztt

In both cases the code works, but I get the same WARNING: Particle 15 will use a fake width ( 1.777e-06 instead of 2.265e-12 ).
Cross-section will be rescaled according to NWA if needed.To force exact treatment reduce the value of 'small_width_treatment' parameter of the run_card

Thank you!

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2019-07-16
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2019-07-16

Hi,

The best way to check the diagrams is to do the following
generate e+ e- > ta+ ta- zp, zp > mu+ mu-, ta+ > mu+ vm vt~, ta- > mu- vt vm~
output /tmp/tmp
display diagrams

But it seems that you understand correctly the syntax.

For the reference, you have:
arXiv:1106.0522<http://arXiv.org/abs/arXiv:1106.0522>
or the command "help generate"

In both cases the code works, but I get the same WARNING: Particle 15 will use a fake width ( 1.777e-06 instead of 2.265e-12 ).
Cross-section will be rescaled according to NWA if needed.To force exact treatment reduce the value of 'small_width_treatment' parameter of the run_card

Thats normal, the width of the tau is too small to have numerical stable result.
So we automatically apply a work-around in order to ensure numerical stability.
You can delay (or forbid) such work-around if you want, but I would bet that in this case, you will
have issue if you do that.

Cheers,

Olivier

On 16 Jul 2019, at 16:52, Igna <<email address hidden><mailto:<email address hidden>>> wrote:

New question #682086 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/682086

I'm looking into the decay chains whose Feynman diagrams I attached bellow. I would like to know if my generation syntax is correct (I'm a bit confused with the use of parenthesis). Where can I find the documentation about the generation syntax and MG?

generate e+ e- > ta+ ta- zp, zp > mu+ mu-, ta+ > mu+ vm vt~, ta- > mu- vt vm~ for https://drive.google.com/file/d/1Sf7CXLbcbibMJiQUVKBFt4JoN2rYkNWh/view?usp=sharing zmm

and

generate e+ e- > mu+ mu- zp, (zp > ta+ ta-, ta+ > mu+ vm vt~, ta- > mu- vt vm~) for

https://drive.google.com/file/d/1AcP0qQjzUOLAQgezoBU0zLWCDwGQRxr0/view?usp=sharing ztt

In both cases the code works, but I get the same WARNING: Particle 15 will use a fake width ( 1.777e-06 instead of 2.265e-12 ).
Cross-section will be rescaled according to NWA if needed.To force exact treatment reduce the value of 'small_width_treatment' parameter of the run_card

Thank you!

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