MadGraph5_aMC@NLO

problem with Inelastic vs Elastic cross section identification

Asked by Matthew Talia

I am generating a process of photoproduction of a 750 GeV resonance:

p p > r j j, r > a a

for some 750 GeV pseudoscalar 'r' coupling to two photons only (and subsequent decay to two photons). This can occur as an inelastic process (where the two protons disintegrate in the final state), semi-elastic, or elastic process. According to relevant of papers on this topic (http://arxiv.org/abs/1601.00638, http://arxiv.org/abs/1512.05751) one should expect inelastic processes to dominate. I want to investigate the differences in these processes in a Madgraph event generation - I have noticed the run-card has a switch 'lpp' which contains 'photons from proton' for each beam separately - though what is the effect of this switch? I have found little or not very significant difference between the cross section calculation in switching both beams to lpp = 1, to lpp = 2, and one beam to lpp = 1 and the other to lpp = 2. How is one to extract information of the inelastic occurring processes compared to the elastic in Madgraph output?

Thanks

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
Last reply:
Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#1

Dear Matthew,

If you are interested in elastic scattering then the correct syntax is
a a > r, r > a a
and you can set lpp=2

The inelastic being
a a > r, r > a a
with lpp=1
Note that for the inelastic, it depends of the PDF that you use some PDF set (like NNPDF) also include the elastic contribution in their fit.
and therefore lpp=1 do not ensure that you have only the inelastic.

The syntax
p p > r j j, r > a a
is a VBF contribution where you do not have any photon in the initial state. and therefore they are no meaning to speak of elastic collision and therefore no meaning of using lpp=2

Cheers,

Olivier

> On Jan 22, 2016, at 02:13, Matthew Talia <email address hidden> wrote:
>
> New question #282131 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/282131
>
> I am generating a process of photoproduction of a 750 GeV resonance:
>
> p p > r j j, r > a a
>
> for some 750 GeV pseudoscalar 'r' coupling to two photons only (and subsequent decay to two photons). This can occur as an inelastic process (where the two protons disintegrate in the final state), semi-elastic, or elastic process. According to relevant of papers on this topic (http://arxiv.org/abs/1601.00638, http://arxiv.org/abs/1512.05751) one should expect inelastic processes to dominate. I want to investigate the differences in these processes in a Madgraph event generation - I have noticed the run-card has a switch 'lpp' which contains 'photons from proton' for each beam separately - though what is the effect of this switch? I have found little or not very significant difference between the cross section calculation in switching both beams to lpp = 1, to lpp = 2, and one beam to lpp = 1 and the other to lpp = 2. How is one to extract information of the inelastic occurring processes compared to the elastic in Madgraph output?
>
> Thanks
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Can you help with this problem?

Provide an answer of your own, or ask Matthew Talia for more information if necessary.

To post a message you must log in.