Madgraph-Pythia interface

Hi Ushoshi,

Pythia8 can't import such type of matrix element (2>4).This is not a MG5 limitation.
This is probably since Pythia 8 can't perform the phase integration efficiently for such diagrams.

My suggestion would be to generate the following matrix element:
p p > w+ l- vl~
and
p p > w- l+ vl
Pythia 8 should be able to decay the on shell W.

Off course by doing this you are going to loose the (important) spin-correlation.
If you care about it (and you probably do) the best is to generate sample of events with MG, and then ask pythia8 to shower those.

Cheers,

Olivier

On Jul 26, 2013, at 1:51 AM, ushoshi maitra <email address hidden> wrote:

> New question #233049 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/233049
>
> Hi
> I'm trying to generate pp > 2l2v via WW* in Madgraph-5. I'm using heft model. Then I want to interface this with Pythia-8. On outputting the process to pythia-8, I'm getting the following error:
> "Command "output pythia8" interrupted with error:
> InvalidCmd : Pythia 8 can only handle 2->1,2,3 processes, not 2->4".
> Would you please suggest me how to resolve this.
>
> Thank You
> Ushoshi
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Thanks a lot.

Ushoshi