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MoMEMta-MaGMEE

MoMEMta - MadGraph Matrix Element Exporter

Note: this version of the exporter tracks the developments of MoMEMta. It may or may not be (though most probably is) compatible with the latest developments. To download a version of the exporter guaranteed to be compatible with a specific release of MoMEMta, select the appropriate branch of this repository.

Requirements

  • Python >= 2.7
  • MG5_aMC@NLO >= 2.5.0 (see here)
  • MoMEMta >= 1.0.0
  • A C++-11 capable compiler

Note: MoMEMta needs to be installed on the system (locally or globally), cf. MoMEMta documentation.

Install

Once your copy of MG5 is setup, go the the PLUGIN subfolder. There, download the MoMEMta-MaGMEE plugin (either by cloning the git repository, or by downloading and extracting the archive).

The MoMEMta-MaGMEE plugin needs to be on PYTHONPATH for it to properly get picked up. If it isn't already, you can prepend it to PYTHONPATH with

export PYTHONPATH=$(python -c 'import madgraph; from pathlib import Path; print(Path(madgraph.MG5DIR).joinpath("PLUGIN", "MoMEMta-MaGMEE"))'):"${PYTHONPATH}"

You are now ready to export matrix elements to use in MoMEMta!

Usage

Example:

  • Go to the MG5 folder
  • Launch MG5: bin/mg5_aMC
  • Generate your favourite process: generate p p > t t~, (t > w+ b, w+ > e+ ve), (t~ > w- b~, w- > e- ve~)
  • Output the process: output MoMEMta myHappyME. myHappyME will be used to define the namespace in which the matrix element code is enclosed, so it has to be a valid C++ variable name.

You now have a folder called myHappyME containing the model's code, a parameter card and the matrix element's code itself.

To build the code and use it in your project, you need to have MoMEMta installed on your system (see the MoMEMta documentation for more details). Then, do:

cmake -S myHappyME -B myHappyME/build
cmake --build myHappyME/build --clean-first --parallel 4

This generates a shared library that can be dynamically loaded by MoMEMta (using the load_modules() function in the Lua config file).

The following options are available when configuring the the build (when running cmake ..):

  • -DCMAKE_INSTALL_PREFIX=(path): Path to the installation of MoMEMta. Must be specified if your version of MoMEMta is installed locally and not in your system directories

The matrix element has a name assigned to it, of type myHappyME_P1_Sigma_pp_ttx_...: this is the name to use when defining the matrix element module in your Lua config file. If you wish to modify it, simply change the name string at the end of the .cc file in the corresponding subfolder of the SubProcesses folder before building the code.