SARAH 4: A tool for (not only SUSY) model builders

Abstract: We present the new version of the Mathematica package SARAH which provides the same features for a non-supersymmetric model as previous versions for supersymmetric models. This includes an easy and straightforward definition of the model, the calculation of all vertices, mass matrices, tadpole equations, and self-energies. Also the two-loop renormalization group equations for a general gauge theory are now included and have been validated with the independent Python code PyR@te. Model files for FeynArts, CalcHep/CompHep, WHIZARD and in the UFO format can be written, and source code for SPheno for the calculation of the mass spectrum, a set of precision observables, and the decay widths and branching ratios of all states can be generated. Furthermore, the new version includes routines to output model files for Vevacious for both, supersymmetric and non-supersymmetric, models. Global symmetries are also supported with this version and by linking Susyno the handling of Lie groups has been improved and extended.

• The paper introduces SARAH 4, which significantly expands support for both SUSY and non-SUSY models through advanced two-loop RGEs validated with independent code.
• It describes how the tool generates model files for simulation packages like UFO, CalcHep, and WHIZARD to streamline phenomenological analyses.
• SARAH 4 enhances the handling of global symmetries and Lie groups, and integrates with Vevacious to assess vacuum stability in beyond Standard Model scenarios.

Overview of SARAH 4: A Tool for Model Building

This paper presents the updated version of the SARAH package, which has been developed by Florian Staub to facilitate model building in particle physics, specifically focusing on both supersymmetric (SUSY) and non-supersymmetric (non-SUSY) models. The latest version, SARAH 4, introduces significant enhancements that expand its applicability beyond SUSY models to embrace non-SUSY theories. These developments are essential for the study of beyond the Standard Model (BSM) physics, as they provide tools for defining models, calculating relevant physical quantities, and interfacing with numerical computation and simulation tools.

Key Features and Improvements

1. Non-Supersymmetric Models: SARAH 4 extends its support to non-SUSY models, offering capabilities that mirror those previously available only for SUSY models. This includes the calculation of vertices, mass matrices, tadpole equations, and self-energies. A substantial addition is the inclusion of two-loop renormalization group equations (RGEs) for general gauge theories, validated against independent code.
2. Model Output and Interface Enhancement: The package can now write model files compatible with various simulation tools such as UFO, CalcHep, and WHIZARD, catering to both SUSY and non-SUSY models. This facilitates the generation of source code for the computation of mass spectra, precision observables, decay widths, and branching ratios.
3. Global Symmetries and Lie Group Handling: The updated version supports global symmetries and improved handling of Lie groups in model definitions. By linking with Susyno, SARAH 4 extends its capability to manage non-SU(N) gauge groups and addresses non-fundamental irreducible representations more effectively.
4. Output for Vevacious: SARAH 4 can generate model files for Vevacious, allowing the examination of the stability of the one-loop effective potential and the lifetime of meta-stable vacua. This feature underscores the importance of examining dangerous vacuum expectation values (VEVs) and the global minimum checks within new physics scenarios.
5. Numerical Evaluation of RGEs: The package is equipped with routines for the numerical evaluation of RGEs using Mathematica, supported by an auxiliary file that simplifies the running and tracking of these equations in the context of high-energy physics.

Numerical Results and Validation

The paper details the performance and accuracy of SARAH 4 through various numerical results, showcasing the tool's efficiency in model initialization and computation. The reported running times on specified hardware demonstrate the tool's adequacy for practical use. Benchmark calculations validate the enhanced RGEs against known cases, affirming compatibility and correctness.

Implications for Future Research

The advancements in SARAH 4 significantly broaden the landscape for model builders in particle physics, particularly for researchers focusing on non-SUSY extensions. By automating detailed calculations and simplifying the integration with simulation tools, SARAH 4 reduces the overhead associated with developing and analyzing complex theoretical models. This fosters a more dynamic exploration of BSM possibilities and can drive research into areas such as dark matter models, extended Higgs sectors, and gauge coupling unification.

Speculation on Future Developments

Looking forward, improvements in SARAH might address further optimization of the interface with Monte Carlo tools, enhancement of the numerical stability of RGE solvers, and inclusion of additional loop-correction features. The growing computational power and evolving theoretical landscape in particle physics may also stimulate the development of SARAH to handle even more complex models efficiently.

In conclusion, SARAH 4 represents a pivotal tool for researchers diving into the intricacies of theoretical physics, supporting a comprehensive workflow from model conception to phenomenological analysis. Its expanded capabilities reaffirm its status as an indispensable asset in the toolkit of particle physicists globally.