Universal Feynman Output (UFO)

The Universal Feynman Output (UFO) is a model format accepted by Monte Carlo event generators such as MadGraph5_aMC@NLO. ExportUFO generates a complete UFO model directory directly from a Matchete Lagrangian, supporting both renormalizable and higher-dimensional operators. Currently, only tree-level UFOs are supported, but the extension to one loop is under development.

Usage 

ExportUFO[L,
  OutputDirectory -> "path/to/ufo/",
  InputFile       -> "path/to/param_card.json"
];

OutputDirectory specifies where the UFO files are written. InputFile points to a JSON parameter card with numerical values for all model parameters. DefaultParamCard generates a template for this card, collecting all parameter names from the model and leaving their numerical values to be filled in:

DefaultParamCard[L, OutputDirectory -> "path/to/params/"];

With DefaultValues -> True, default SM input values are inserted automatically for simple SM-based models. When flavor symmetries have been imposed via ImposeFlavorSymmetry, pass the resulting flavor structures through the FlavorInvariants option so that the parameter card reflects the reduced set of independent couplings:

flavorStructures = ImposeFlavorSymmetry[L, symmetrySpec];
DefaultParamCard[L, FlavorInvariants -> flavorStructures];

Coupling orders

UFO allows each interaction vertex to carry coupling orders (e.g., QCD (required), QED, or a new-physics order). Coupling orders are defined with DefineCouplingOrder which directly associates them to the individual couplings:

(* Declare coupling orders: name, couplings, hierarchy *)
DefineCouplingOrder["QED", e,  2];
DefineCouplingOrder["QCD", gs, 1];

The third argument to DefineCouplingOrder sets the relative hierarchy among orders. In the example above, two insertions of the QCD coupling should be considered the same order as one insertion of the QED coupling. The helper functions GetCouplingOrders, RemoveCouplingOrder, and ResetCouplingOrders manage these definitions.

Notes

  • For theories defined in the symmetric phase, spontaneous symmetry breaking should be applied first; pass the resulting broken-phase Lagrangian to ExportUFO.
  • The ImposeFlavorSymmetry function allows one to exploit flavor symmetries to reduce the number of independent couplings in the UFO output.
  • Detailed tutorials covering the UFO workflow for SMEFT Feynman rules and for generic BSM-to-EFT models are available in the documentation.