Plot of R-ratio for a QED process at various beam energies

Asked by Akanksha Singh on 2020-05-03

Hello.I am new to madgraph and I need help with plotting a graph of R-ratio for a particular process at different beam energies.The process I am looking at is (e+ e- going to mu+ mu- ).
1. I think that plotting of R-ratio will require LHE file containing total cross-section of all the hadrons that can be created at that beam energy, that is e+ e- going to all the hadrons at that energy.How can I create such an LHE file?
2.Then I will need the LHE file for the actual process.The process that I am looking at is e+ e- going to mu+ mu- .So i will create LHE file of this process.Then I need to define a variable which will be the ratio of the total croo-section of (e+ e- going to hadrons) and that of (e+ e- going to mu+ mu-).How can I do this?Can this be done directly in Madgraph or will I have to use other tools? Can I use Pythia and Root to do this?Regarding Pythia,can I write a program in C++ which will retrieve information of total cross-section from the LHE files and calculate R-ratio?If yes,how can I do this?I mean how do I call the cross-section from the LHE file?
 If this is not the correct way to do this then what can I do to plot this graph?

Thanks in advance.

Question information

Language:
English Edit question
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Answered
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MadGraph5_aMC@NLO Edit question
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Last query:
2020-05-03
Last reply:
2020-05-03

Hi,

I do not know the variable that you are looking at. So my answer might not be correct.
What I would try is to look at the cross-section of
e+ e- > j j
and to the one of
e+ e- > mu+ mu-
and do the ratio

You do not need to parse the lhe file since you do not need differential cross-section.

Cheers,

Olivier

> On 3 May 2020, at 06:47, Akanksha Singh <email address hidden> wrote:
>
> New question #690417 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/690417
>
> Hello.I am new to madgraph and I need help with plotting a graph of R-ratio for a particular process at different beam energies.The process I am looking at is (e+ e- going to mu+ mu- ).
> 1. I think that plotting of R-ratio will require LHE file containing total cross-section of all the hadrons that can be created at that beam energy, that is e+ e- going to all the hadrons at that energy.How can I create such an LHE file?
> 2.Then I will need the LHE file for the actual process.The process that I am looking at is e+ e- going to mu+ mu- .So i will create LHE file of this process.Then I need to define a variable which will be the ratio of the total croo-section of (e+ e- going to hadrons) and that of (e+ e- going to mu+ mu-).How can I do this?Can this be done directly in Madgraph or will I have to use other tools? Can I use Pythia and Root to do this?Regarding Pythia,can I write a program in C++ which will retrieve information of total cross-section from the LHE files and calculate R-ratio?If yes,how can I do this?I mean how do I call the cross-section from the LHE file?
> If this is not the correct way to do this then what can I do to plot this graph?
>
> Thanks in advance.
>
> --
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