Madflow

If you use this software please cite this paper

@article{madflow,
    author = "Carrazza, Stefano and Cruz-Martinez, Juan and Rossi, Marco and Zaro, Marco",
    title = "{MadFlow: automating Monte Carlo simulation on GPU for particle physics processes}",
    eprint = "2106.10279",
    archivePrefix = "arXiv",
    primaryClass = "physics.comp-ph",
    reportNumber = "TIF-UNIMI-2021-9",
    doi = "10.1140/epjc/s10052-021-09443-8",
    journal = "Eur. Phys. J. C",
    volume = "81",
    number = "7",
    pages = "656",
    year = "2021"
}

Install madflow

From PyPI

    pip install madflow

From the repository

  git clone https://github.com/N3PDF/madflow.git
  cd madflow
  pip install .

External tools

madflow relies in a number of external tools. Some of them are just used for convenience and are optional, some are necessary for the proper functioning of the program.

MG5_aMC

A valid installation of MG5_aMC (2.8+) is necessary in order to generate matrix elements. If you already have a valid installation, please add the following environment variable pointing to the right directory: MADGRAPH_PATH. Below are the instructions for MG5_aMC 3.1.0, for a more recent release please visit the MG5_aMC@NLO site.

wget https://launchpad.net/mg5amcnlo/3.0/3.1.x/+download/MG5_aMC_v3.1.0.tar.gz
tar xfz MG5_aMC_v3.1.0.tar.gz
export MADGRAPH_PATH=${PWD}/MG5_aMC_v3_1_0

PDF grids

While LHAPDF is not strictly necessary to use the madflow library or run any of the scripts, having access to the lhapdf python wrapper can be convenient in order to manage the different PDFsets. Please install the latest version from the LHAPDF site.

Otherwise, if your installed version of pdfflow is equal or greater than 1.2.2, it includes the lhapdf-management scripts suite and LHAPDF should not be needed. You can also manually install the PDF sets in a suitable directory and ensure that either the PDFFLOW_DATA_PATH or LHAPDF_DATA_PATH environment variables are pointing to it.

You can check your installed version of pdfflow with: python -c 'import pdfflow ; print(pdfflow.__version__);'

Install plugin in MG5_aMC

In order to install the madflow plugin in MG5_aMC@NLO, it is necessary to link the madgraph_plugin folder inside the PLUGIN directory of MG5_aMC@NLO. For instance, if the environment variable $MADGRAPH_PATH is pointing to the MG5_aMC root and you are currently in the repository root.

    ln -s ${PWD}/madgraph_plugin ${MADGRAPH_PATH}/PLUGIN/pyout

The link can be performed automagically with the madflow --autolink option.

Use madflow

For a more precise description of what madflow can do please visit the online documentation.

For convenience a script is provided which should have been installed alongside the library. Using this script is possible to run any process at Leading Order, integrated with a RAMBO-like phasespace.

  madflow --help

    [-h] [-v] [-p PDF] [--no_pdf] [-c] [--madgraph_process MADGRAPH_PROCESS] [-m MASSIVE_PARTICLES] [-g] [--pt_cut PT_CUT] [--histograms]

    optional arguments:
      -h, --help            show this help message and exit
      -v, --verbose         Print extra info
      -p PDF, --pdf PDF     PDF set
      --no_pdf              Don't use a PDF for the initial state
      -c, --enable_cuts     Enable the cuts
      --madgraph_process MADGRAPH_PROCESS
                            Set the madgraph process to be run
      -m MASSIVE_PARTICLES, --massive_particles MASSIVE_PARTICLES
                            Number of massive particles
      -g, --variable_g      Use variable g_s
      --pt_cut PT_CUT       Minimum pt for the outgoint particles
      --histograms          Generate LHE files/histograms