Introduction

If you install Pythia from within MadGraph5, you get Pythia6. I would like to set up Pythia8, so I can validate the matching parameters I configure there.

I am taking instructions from a few different sources:

• http://home.thep.lu.se/~torbjorn/pythia8/mergingworksheet8160.pdf
• https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/MadGraphForAtlas#matching_of_matrix_element_ME_an
• https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/AtlasMcProductionMC12#Production_validation_releases
• https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/MadGraphMatching#Preparing_MadGraph5_for_matching
• https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/MadGraphInProdSys

Steps taken

• Download Pythia8 from the web and install: http://home.thep.lu.se/~torbjorn/Pythia.html
• One can generate a Pythia8 process from within MadGraph. To do this, you set up your model in the normal way, then you can output the new process using the following command from within mg5:

  output pythia8 [path_to_pythia81xx_directory]

• There is also something about setting the pythia8_path in the me5_configuration.dat card. This looks something like this:

        pythia8_path = rel/path/to/pyhtia8/from/MG5/dir

• Something else to note. Since I am working from the MSSM model, and fixing the SLHA param card by hand, it will be necessary to copy the correct SLHA param card to the Pythia8 directory as well. (I think... Maybe there is a way to read it from the LHE...)

-- BrettJackson - 05 Dec 2013