Charged particle as missing energy

Hi Manuel,

> a) Is there a way to tell Pythia and PGS to treat xpm as missing energy? I already tried what says in this thread: https://answers.launchpad.net/mg5amcnlo/+question/239651

This is a question for the author of those code. Nothing that I can help you with.

> b) Should I instead make sure Pythia is decaying my xpm? How do I do this? I added a width to my particle definitions but Pythia doesn’t do anything with it.

This is your choice but if you want to treat it as missing energy, it sounds weird to decay it.
In order to make the decay in pythia, you need to provide the Branching Ratio table in the param_card.
MadWidth (arXiv:1402.1178) is able to compute those automatically if needed.
Basically you just have to put Auto for the width. and MadWidth will be called automatically.

> c) Should I generate processes in which I explicitely tell MG to decay my xpm (like p p > j x0 x+, (x+ > x0 u d~ $ w+) )? If I do this, though, I don't get any events (a banner like in https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-14 appears).

What is the width of x+? if you put that width to zero then the cross-section is analytically infinite. (As said above you can use MadWidth to compute the Leading order width automatically)

Cheers,

Olivier

On 04 Feb 2015, at 23:07, Manuel <email address hidden> wrote:

> New question #261684 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/261684
>
> Hello, everyone:
>
> I'm running MG + Pythia + PGS with a model in which I have a neutralino-like particle (x0) as well as a slightly heavier charged fermion (xpm) that decays to this x0 and soft pions. I'm generating events in which x0 and xpm are produced and all of this should be seen as missing energy in a detector. In other words, I'm generating processes like:
>
> p p > j x0 x+
> p p > j x0 x-
> p p > j x+ x-
>
> I managed to make Pythia and PGS ignore my x0 as missing energy by assigning to it the PDG of the smallest neutralino, but when running MA5 and, say, plotting NAPID, I still get a lot of 9000005 particles (the PDG code automatically assigned to my xpm).
>
> My question is trying to solve this and make my xpm also look like missing energy. What should I do?
>
> a) Is there a way to tell Pythia and PGS to treat xpm as missing energy? I already tried what says in this thread: https://answers.launchpad.net/mg5amcnlo/+question/239651
>
> b) Should I instead make sure Pythia is decaying my xpm? How do I do this? I added a width to my particle definitions but Pythia doesn't do anything with it.
>
> c) Should I generate processes in which I explicitely tell MG to decay my xpm (like p p > j x0 x+, (x+ > x0 u d~ $ w+) )? If I do this, though, I don't get any events (a banner like in https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-14 appears).
>
> d) Something else?
>
> Thanks for your help.
>
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