Photon radiation in single top

Asked by Kirill Skovpen on 2021-03-27

Hello,

Is it possible to generate the t channel single top production process with photon radiation included in all possible cases?

If I understand correctly, the photon radiation can not be done via MadSpin. The attemps of this sort:

p p > t j a $$ w+ w-, (t > l+ vl b)

would, of course, result in the photon radiation be missed off the decay products of the top quark. Is there any alternative syntax?

Thanks,

Kirill

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Last query:
2021-03-28
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2021-03-28

This question was reopened

You need to go to something like

> p p > l+ vl b j a

Cheers,

Olivier

> On 27 Mar 2021, at 22:55, Kirill Skovpen <email address hidden> wrote:
>
> New question #696278 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/696278
>
> Hello,
>
> Is it possible to generate the t channel single top production process with photon radiation included in all possible cases?
>
> If I understand correctly, the photon radiation can not be done via MadSpin. The attemps of this sort:
>
> p p > t j a $$ w+ w-, (t > l+ vl b)
>
> would, of course, result in the photon radiation be missed off the decay products of the top quark. Is there any alternative syntax?
>
> Thanks,
>
> Kirill
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks Olivier.

I tried a similar approach, but it results in diagrams without top quark.

Yes, I'm not sure you can force to always have a top in gauge invariant way:

I tried the syntax
check p p > t > l+ vl b j a

and this is not gauge invariant (and as a consequence the result is not lorentz invariant0
(see details below)

So you will need to play with diagram filtering in order to keep a subset of gauge invariant diagram.
such that your computation is meaningfull.

Cheers,

Olivier

> Lorentz invariance results:
> Process Min element Max element Relative diff. Result
> u d~ > e+ ve b b~2.3837331329e-21 2.3837331329e-21 5.2548112997e-14 Passed
> u d~ > mu+ vm b b7.1720001950e-18 7.4431024171e-18 3.6423282514e-02 Failed
> JAMP 0 2.8688000780e-17 2.9772409668e-17 3.6423282514e-02 Failed
> c s~ > e+ ve b b~3.9740211139e-22 6.0968645467e-22 3.4818609082e-01 Failed
> JAMP 0 1.5896084456e-21 2.4387458187e-21 3.4818609082e-01 Failed
> c s~ > mu+ vm b b1.0618374958e-16 1.3936892438e-16 2.3811028856e-01 Failed
> JAMP 0 4.2473499832e-16 5.5747569752e-16 2.3811028856e-01 Failed
> Summary: 1/4 passed, 3/4 failed
> Failed processes: u d~ > mu+ vm b b~ a, c s~ > e+ ve b b~ a, c s~ > mu+ vm b b~ a
> Gauge results:
> Process matrix BRS ratio Result
> u d~ > e+ ve b b~ a 4.3678332224e-22 1.1893802960e-49 2.7230442085e-28 Passed
> Summary: 1/1 passed, 0/1 failed
> Gauge results (switching between Unitary/Feynman/axial gauge):
> Process Unitary Feynman Relative diff. Result
> u d~ > e+ ve b b~ a 2.5756656229e-20 1.4009706727e-20 4.5607432104e-01 Failed
> JAMP 0 1.0302662492e-19 5.6038826909e-20 4.5607432104e-01 Failed
> u d~ > mu+ vm b b~ a 1.2601737500e-19 1.2331897409e-19 2.1412927473e-02 Failed
> JAMP 0 5.0406950000e-19 4.9327589635e-19 2.1412927473e-02 Failed
> c s~ > e+ ve b b~ a 2.7396796584e-19 2.4481594841e-19 1.0640666455e-01 Failed
> JAMP 0 1.0958718634e-18 9.7926379362e-19 1.0640666455e-01 Failed
> c s~ > mu+ vm b b~ a 4.1242031885e-20 5.4337024317e-20 2.4099575928e-01 Failed
> JAMP 0 1.6496812754e-19 2.1734809727e-19 2.4099575928e-01 Failed
> Summary: 0/4 passed, 4/4 failed
> Failed processes: u d~ > e+ ve b b~ a, u d~ > mu+ vm b b~ a, c s~ > e+ ve b b~ a, c s~ > mu+ vm b b~ a
> Process permutation results:
> Process Min element Max element Relative diff. Result
> u d~ > e+ ve b b~ a 9.7709644340e-18 9.7709644340e-18 1.1038017548e-15 Passed
> Summary: 1/1 passed, 0/1 failed

> On 27 Mar 2021, at 23:35, Kirill Skovpen <email address hidden> wrote:
>
> Question #696278 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/696278
>
> Status: Answered => Open
>
> Kirill Skovpen is still having a problem:
> Thanks Olivier.
>
> I tried a similar approach, but it results in diagrams without top
> quark.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks Olivier Mattelaer, that solved my question.

Sorry, just a quick follow-up question. Is it possible to run the 'check' together with --diagram_filter in order to validate the gauge invariance of the event generation when removing diagrams?

I do not think so.

Cheers,

Olivier

> On 28 Mar 2021, at 10:41, Kirill Skovpen <email address hidden> wrote:
>
> Question #696278 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/696278
>
> Status: Solved => Open
>
> Kirill Skovpen is still having a problem:
> Sorry, just a quick follow-up question. Is it possible to run the
> 'check' together with --diagram_filter in order to validate the gauge
> invariance of the event generation when removing diagrams?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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