Change density of proton beams & isotropic production of particles

Asked by Ameir Shaa on 2017-12-27

Hello MadGraph Team,

I am trying to simulate a fixed target collision as accurately as possible. To this end, I wonder if it is possible to change the density of one of the incoming proton beams. For example, lets suppose the default is that both the incoming beams have 2686 protons in one bunch and I would like to change the value of 2686 to 3686 (as an example) for one of the beams. Is this possible in MadGraph?

Also, is it possible to isotropically create particles like muons? (i.e. simulate a particle gun that "shoots" out muons?)

I apologize in advance if these questions seem very trivial.

Many thanks,

Ameir

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Solved by:
Olivier Mattelaer
Solved:
2017-12-28
Last query:
2017-12-28
Last reply:
2017-12-28

Hi,

The short answer to your question is probably "no" to both question since I do not really understand what you try to ask.

> For example, lets suppose the default is that both the incoming beams have 2686 protons in one bunch and I would like to change the value of 2686 to 3686 (as an example) for one of the beams. Is this possible in MadGraph?

To my point of view, the only impact of the number of proton in a bunch is for pile up. This effect is not include at the MG5aMC model but rather at the detector simulation level.
(For example, Delphes can simulate the pile-up). Now you might want to study some other effect which might be include in the non perturbative model of the hadronization algorithm (which in that case is part of pythia/pgs tuning).

But clearly, we do not have any "number of proton in one bunch" in MG5aMC.

> Also, is it possible to isotropically create particles like muons? (i.e. simulate a particle gun that "shoots" out muons?)

Here I do not see the point of using MG5aMC (where do you need the matrix-element square for this?).
First your statement seems frame dependent, since if you go to the rest-frame of the muon, you will always have them at rest.
But if I would need to do that,

I would just do it with some routine like:
import random
from math import *
theta = pi * random.random()
phi = 2*pi * random.random()
p = 100
E = p #assume massless
px = p *cos(theta)*cos(phi)
py = p * cos(theta)*sin(phi)
pz = p* sin(theta)

Cheers,

Olivier

> On 27 Dec 2017, at 18:22, Ameir Shaa <email address hidden> wrote:
>
> New question #662291 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/662291
>
> Hello MadGraph Team,
>
> I am trying to simulate a fixed target collision as accurately as possible. To this end, I wonder if it is possible to change the density of one of the incoming proton beams. For example, lets suppose the default is that both the incoming beams have 2686 protons in one bunch and I would like to change the value of 2686 to 3686 (as an example) for one of the beams. Is this possible in MadGraph?
>
> Also, is it possible to isotropically create particles like muons? (i.e. simulate a particle gun that "shoots" out muons?)
>
> I apologize in advance if these questions seem very trivial.
>
> Many thanks,
>
> Ameir
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Ameir Shaa (ameirshaa) said : #2

Hi Olivier,

Many thanks for your swift reply!

Many thanks,

Ameir

Ameir Shaa (ameirshaa) said : #3

Thanks Olivier Mattelaer, that solved my question.