FlexibleDecay: An automated calculator of scalar decay widths

Peter Athron, Adam Büchner, Dylan Harries, Wojciech Kotlarski, Dominik Stöckinger, Alexander Voigt

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We present FlexibleDecay, a tool to calculate decays of scalars in a broad class of BSM models. The tool aims for high precision particularly in the case of Higgs boson decays. In the case of scalar and pseudoscalar Higgs boson decays the known higher order SM QED, QCD and EW effects are taken into account where possible. The program works in a modified MS‾ scheme that exhibits a decoupling property with respect to heavy BSM physics, with BSM parameters themselves treated in the MS‾/DR‾-scheme allowing for an easy connection to high scale tests for, e.g., perturbativity and vacuum stability, and the many observable calculations readily available in MS‾/DR‾ programs. Pure BSM effects are taken into account at the leading order, including all one-loop contributions to loop-induced processes. The program is implemented as an extension to FlexibleSUSY, which determines the mass spectrum for arbitrary BSM models, and does not require any extra configuration from the user. We compare our predictions for Higgs decays in the SM, singlet extended SM, type II THDM, CMSSM and MRSSM, as well as for squark decays in the CMSSM against a selection of publicly available tools. The numerical differences between our and other programs are explained. The release of FlexibleDecay officially deprecates the old effective couplings routines in FlexibleSUSY. Program summary: Program Title: FlexibleDecay CPC Library link to program files: https://doi.org/10.17632/2c38hcpp5n.1 Developer's repository link: https://github.com/FlexibleSUSY/FlexibleSUSY Licensing provisions: GPLv3 Programming language: C++, Wolfram Language, Fortran, Bourne shell Nature of problem: Calculation of decay widths of scalar bosons in extensions of the Standard Model of particle physics. For the calculation of Higgs boson decay widths known higher-order contributions are taken into account to achieve a high precision. Solution method: The decay widths of the scalar bosons are expressed in terms of Feynman diagrams in a general renormalizable quantum field theory and specialized to the considered model. The resulting expressions are numerically evaluated using special functions and numerical integration. Additional comments including restrictions and unusual features: FlexibleDecay is an addon to FlexibleSUSY [1, 2]. The decay widths can only be calculated in models that can be treated with FlexibleSUSY. Decay widths of fermions or vector bosons are not calculated. For non-Higgs scalar bosons the calculation is restricted to the leading order in the perturbation series. References: [1] P. Athron, J.h. Park, D. Stöckinger, A. Voigt, Comput. Phys. Commun. 190 (2015) 139–172, https://doi.org/10.1016/j.cpc.2014.12.020, arXiv:1406.2319 [hep-ph]. [2] P. Athron, M. Bach, D. Harries, T. Kwasnitza, J.h. Park, D. Stöckinger, A. Voigt, J. Ziebell, Comput. Phys. Commun. 230 (2018) 145–217, https://doi.org/10.1016/j.cpc.2018.04.016, arXiv:1710.03760 [hep-ph].

Original languageEnglish
Article number108584
JournalComputer Physics Communications
Publication statusPublished or Issued - Feb 2023
Externally publishedYes


  • BSM
  • Decays
  • Higgs boson

ASJC Scopus subject areas

  • Hardware and Architecture
  • Physics and Astronomy(all)

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