Bhaba Scattering with ISR photon

Asked by SAUMYEN KUNDU on 2020-02-06

Hi,
I wanted to generate events for the Bhaba scattering with an extra ISR photon. But when I give "generate e- e+ > e- e+ a", it's diagrams include other processes also, as it should be, of course. So, is there any particular syntax so that the photon comes only from initial state radiation?

Thanks in advance and regards,
Saumyen

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2020-02-06
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2020-02-06

Hi,

Not sure if this is what you want but maybe what you are looking for is something like
generate a a > mu+ mu-

and then in the run_card you can set the lpp1 and lpp2 paramter to photon from electron (should be value 2 or 3)

Cheers,

Olivier

> On 6 Feb 2020, at 15:17, SAUMYEN KUNDU <email address hidden> wrote:
>
> New question #688557 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/688557
>
> Hi,
> I wanted to generate events for the Bhaba scattering with an extra ISR photon. But when I give "generate e- e+ > e- e+ a", it's diagrams include other processes also, as it should be, of course. So, is there any particular syntax so that the photon comes only from initial state radiation?
>
> Thanks in advance and regards,
> Saumyen
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

SAUMYEN KUNDU (saumyen.k) said : #2

Thanks Olivier for the response.

No, basically, in this case, my final state particles will be (e-e+a), where 'a' will come from initial state radiation of either e- or e+. That's why I put "generate e- e+ > e- e+ a". But that's including other diagrams also as expected.

Regards,

Saumyen

So no we do not have a syntax for that.
This is going to break gauge invariance (and consequently lorentz invariance).

You can technically filter your diagram if you need (assuming that your subset is indeed gauge invariant)

Cheers,

Olivier

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