# mssm multiparticles

Asked by Gabriele Ferretti on 2015-06-07

Hi,
I noticed something strange with the multiparticle definition in the mssm.

As a trivial example, suppose I generate stop decay in a simplified model containing only t1 t1~ and n1

import model mssm

define heavy = go ul cl ur cr t2 dl sl b1 dr sr b2 ul~ cl~ ur~ cr~ t2~ dl~ sl~ b1~ dr~ sr~ b2~ sve svm svt el- mul- ta1- er- mur- ta2- h+ h2 h3 sve~ svm~ svt~ el+ mul+ ta1+ er+ mur+ ta2+ h- n2 n3 n4 x1+ x2+ x1- x2-

generate t1 > n1 b w+ /heavy

The output I get on the terminal says:
INFO: Trying process: t1 > n1 b w+ / go ul cl ur cr t2 dl sl b1 dr sr b2 ul cl ur cr t2 dl sl b1 dr sr b2 sve svm svt el- mul- ta1- er- mur- ta2- h+ h2 h3 sve svm svt el- mul- ta1- er- mur- ta2- h+ n2 n3 n4 x1+ x2+ x1+ x2+
INFO: Process has 1 diagrams
1 processes with 1 diagrams generated in 0.003 s
Total: 1 processes with 1 diagrams

If you look at the particle list after the / you see that the charges of some particles are reversed (e.g. the charginos are only positive and the sleptons negative). Everything else works fine and it's probably OK but I though of pointing it out in case it leads to problems in more complicated processes.

Cheers
Gabriele

## Question information

Language:
English Edit question
Status:
For:
Assignee:
No assignee Edit question
Last query:
2015-06-07
2015-06-07
 Olivier Mattelaer (olivier-mattelaer) said on 2015-06-07: #1

Hi,

This is normal, “/“ remove the particle and the anti-particle.
The reason is the “/“ acts on T-channel where the definition of a particle/antiparticle is a matter of choice.

Cheers,

Olivier

On 07 Jun 2015, at 14:51, Gabriele Ferretti <email address hidden> wrote:

> New question #267860 on MadGraph5_aMC@NLO:
>
> Hi,
> I noticed something strange with the multiparticle definition in the mssm.
>
> As a trivial example, suppose I generate stop decay in a simplified model containing only t1 t1~ and n1
>
> import model mssm
>
> define heavy = go ul cl ur cr t2 dl sl b1 dr sr b2 ul~ cl~ ur~ cr~ t2~ dl~ sl~ b1~ dr~ sr~ b2~ sve svm svt el- mul- ta1- er- mur- ta2- h+ h2 h3 sve~ svm~ svt~ el+ mul+ ta1+ er+ mur+ ta2+ h- n2 n3 n4 x1+ x2+ x1- x2-
>
> generate t1 > n1 b w+ /heavy
>
> The output I get on the terminal says:
> INFO: Trying process: t1 > n1 b w+ / go ul cl ur cr t2 dl sl b1 dr sr b2 ul cl ur cr t2 dl sl b1 dr sr b2 sve svm svt el- mul- ta1- er- mur- ta2- h+ h2 h3 sve svm svt el- mul- ta1- er- mur- ta2- h+ n2 n3 n4 x1+ x2+ x1+ x2+
> INFO: Process has 1 diagrams
> 1 processes with 1 diagrams generated in 0.003 s
> Total: 1 processes with 1 diagrams
>
> If you look at the particle list after the / you see that the charges of some particles are reversed (e.g. the charginos are only positive and the sleptons negative). Everything else works fine and it's probably OK but I though of pointing it out in case it leads to problems in more complicated processes.
>
> Cheers
> Gabriele
>
> --