Computing decay rates for new physics theories with FEYNRULES and MADGRAPH 5_AMC@NLO

We present new features of the FEYNRULES and MADGRAPH 5_AMC@NLO programs for the automatic computation of decay widths that consistently include channels of arbitrary final-state multiplicity. The implementations are generic enough so that they can be used in the framework of any quantum field theory, possibly including higher-dimensional operators. We extend at the same time the conventions of the Universal FEYNRULES Output (or UFO) format to include decay tables and information on the total widths. We finally provide a set of representative examples of the usage of the new functions of the different codes in the framework of the Standard Model, the Higgs Effective Field Theory, the Strongly Interacting Light Higgs model and the Minimal Supersymmetric Standard Model and compare the results to available literature and programs for validation purposes. Program summary Program title: MadWidth Catalogue identifier: AEXY_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEXY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1854258 No. of bytes in distributed program, including test data, etc.: 21136244 Distribution format: tar.gz Programming language: Mathematica and Python. Computer: Platforms on which Mathematica and Python are available. Operating system: Operating systems on which Mathematica and Python are available. Classification: 11.1, 11.6. External routines: FeynRules 2.0 or higher, MadGraph5_aMC@NLO 2.2 or higher. Nature of problem: The program is a module for the FeynRules and MadGraph5_aMC@NLO packages that allows the computation of tree-level decay widths for arbitrary BSM models. The module consists of two parts: 1. A FeynRules part, which allows one to compute analytically all tree-level two-body decay rates and to output them in the UFO format. 2. A MadGraph5_aMC@NLO part, which allows the numerical computation of many-body decay rates. Solution method: 1. For the FeynRules part, the analytic expressions for the three-point vertices can be squared to obtain analytic formulas for two-body decay rates. 2. For the MadGraph5_aMC@NLO part, MadGraph is used to generate all Feynman diagrams contributing to the decay, and diagrams that correspond to cascade decays are removed. Restrictions: Mathematica version 7 to 9. As the package is a module relying on FeynRules and MadGraph5_aMC@NLO all restrictions of these packages apply. Running time: The computation of the Feynman rules from a Lagrangian, as well as the computation of the decay rates, varies with the complexity of the model, and runs from a few seconds to several minutes. See Section 5 of the present manuscript for more information. (C) 2015 Elsevier B.V. All rights reserved.