ISR with MadWeight5 in MG5_aMC@NLO v2.7.2

Hi,

MadWeight is not supported anymore and we advice to use Momenta instead.
This being said MadWeight is still included in 2.7.2 and prior to each release we check that it still returns expected weight for a couple of process and that speed is reasonable.

> have seen old tutorials which show it is possible to use MadWeight5 to
> reweight the calculated matrix element in MadGraph's event generation to
> include ISR effects (particularly transverse boosts);

I do not remember the details of what is included in the code, but I remember that I was never happy with the way that was implemented in the public version.

Cheers,

Olivier

> On 22 Jun 2020, at 22:05, Al Bee <email address hidden> wrote:
>
> Question #691473 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/691473
>
> Description changed to:
> Hi MadTeam,
>
> I have seen old tutorials which show it is possible to use MadWeight5 to
> reweight the calculated matrix element in MadGraph's event generation to
> include ISR effects (particularly transverse boosts); however, the
> current release version of MG5_aMC@NLO (v2.7.2) doesn't seem to include
> MadWeight. (At least, not with much of the old functionality like:
> `output madweight PATH`)
>
> Is there some way to do this without MW now? I guess maybe through the
> reweight functionality? If so, can it still be done prior to/separately
> from parton showering through Pythia/Herwig?
>
> Thanks,
> Al Bee
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

Thanks for the information. By Momenta, I guess you mean this package here: https://momemta.github.io/ and here https://github.com/MoMEMta ?
Do you have any advice on how to include ISR effects using Momemta? Normally I would ask the developers of this project directly, but it seems that github has not seen activity since 2018.

Thanks,
AB

One big difference between MW and momenta is that momenta let you define your change of variable (from the MW building block and others) while MW does a default choice for you.

For ISR, I'm not convince that MW does a very good job in choosing such change of variable, so Momenta should be better since it put you in control. Now I do not have any experience in Momenta so far.

Cheers,

Olivier