UFO

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To generate model files in the UFO  format which can be used e.g. with Madgraph ,

ModelOutput[$EIGENSTATES, WriteUFO->True]

is used.If the vertices have been calculated already by MakeVertexList or ModelOutput,

MakeUFO[options]

can be used. The possible options are

  1. Exclude, Values: list of generic type, Default: {SSSS,GGS,GGV}
    Defines, which generic diagrams are excluded when writing the model file

The output written by SARAH consists of the files

  • particles.py: contains the particles present in the model
  • parameters.py: contains all parameters present in the model
  • lorentz.py: defines the Lorentz structures needed for the vertices
  • vertices.py: defines the vertices
  • couplings.py: expressions to calculate the couplings
  • coupling_orders.py: defines hierarchies for the coupling orders

These files are saved in the directory

 $SARAH/Output/$MODEL/$EIGENSTATES/UFO/

This directory contains also additional files which are model independent and can therefore be used with all models: function_library.py, object_library.py, __init__.py and write_param_card.py. These files were kindly provided by Olivier Mattelaer.

Using the UFO model files of SARAH with Madgraph 

To use the model files with Madgraph , it is sufficient to copy all files to $MADGRAPH/models/$NAME. Here, $MADGRAPH is the directory containing the local Madgraph installation and $NAME is a freely-chosen name of a new subdirectory. This directory name is used afterwards to load the model in Madgraph via

> import model $NAME

Madgraph has a list of pre-defined names for the particles of the SM and MSSM which are used by default. However, it could be that there are conflicts between these names and the names used by SARAH in an extension of the MSSM. For instance, h3 is defined in Madgraph as the pseudoscalar Higgs in the MSSM, but SARAH uses it in the NMSSM for the third-heaviest scalar Higgs. In order to avoid such clashes, a model can be loaded using only the names defined by the UFO files via

> import model $NAME -modelname

To use these model files for the calculation of cross sections, it is, of course, necessary to provide the numerical values of all masses and parameters. The necessary input can be obtained by using a SPheno module created by SARAH for the given model. The SLHA spectrum files written by this SPheno module can directly be used with Madgraph .

See also