How to run the parton-shower multiple times on the same LHE file

Hi,

Yes you can.

You need to launch manually what we call the “run interface” of the process directory.

From the process directory you can type
./bin/madevent
or
./bin/aMCatNLO
depending if you run with LO/NLO matrix elements
alternatively, you can access this interface from the MG5 interface via
launch PATH -i

at that level, you will have the same kind of interface as created by ./bin/mg5_aMC
but with different command available.
you can type help to see the list of available command.

at LO, you should be interested in the following two command
pythia
pythia8
at NLO, you should be interested in the command
shower

I would advise you to type help NAME to see the exact syntax in each case.
But for pythia8 the syntax is for example
pythia8 run_01
(run_01 is the name of the run creating the lhe file)

Cheers,

Olivier

PS: You can also run the shower directly (as described in the shower program manual) on the lhe generated file

> On Nov 22, 2016, at 21:42, Riccardo Di Sipio <email address hidden> wrote:
>
> New question #404308 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/404308
>
> Hi,
>
> I'm performing some studies on the systematic uncertainty associated with parton-showering. Is there a neat way to run the PS within MG5 many times on the same LHE file? I don't want to re-generate the matrix elements all the times, as I would like to modify the file before the PS.
>
> Cheers,
> Riccardo
>
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