HiggsBounds-4: Improved Tests of Extended Higgs Sectors against Exclusion Bounds from LEP, the Tevatron and the LHC

Abstract: We describe the new developments in version 4 of the public computer code HiggsBounds. HiggsBounds is a tool to test models with arbitrary Higgs sectors, containing both neutral and charged Higgs bosons, against the published exclusion bounds from Higgs searches at the LEP, Tevatron and LHC experiments. From the model predictions for the Higgs masses, branching ratios, production cross sections and total decay widths - which are specified by the user in the input for the program - the code calculates the predicted signal rates for the search channels considered in the experimental data. The signal rates are compared to the expected and observed cross section limits from the Higgs searches to determine whether a point in the model parameter space is excluded at 95% confidence level. In this document we present a modification of the HiggsBounds main algorithm that extends the exclusion test in order to ensure that it provides useful results in the presence of one or more significant excesses in the data, corresponding to potential Higgs signals. We also describe a new method to test whether the limits from an experimental search performed under certain model assumptions can be applied to a different theoretical model. Further developments discussed here include a framework to take into account theoretical uncertainties on the Higgs mass predictions, and the possibility to obtain the $\chi^2$ likelihood of Higgs exclusion limits from LEP. Extensions to the user subroutines from earlier versions of HiggsBounds are described. The new features are demonstrated by additional example programs.

• The paper updates a Fortran code for exclusion tests, incorporating algorithms that handle excesses in experimental data.
• It introduces a framework to account for theoretical uncertainties in Higgs mass predictions and supports expanded input formats like SLHA.
• The improved tool seamlessly bridges theoretical predictions with experimental limits from LEP, Tevatron, and LHC data.

Review of "Improved Tests of Extended Higgs Sectors against Exclusion Bounds from LEP, the Tevatron and the LHC"

This paper presents version 4 of the public Fortran code, a tool designed to test models with arbitrary Higgs sectors against exclusion bounds from experiments at LEP, the Tevatron, and the LHC. The primary purpose of this software is to provide a framework for comparing complex theoretical predictions from extended Higgs sectors with experimental data, thus facilitating the interpretation of these models in light of non-observation data from various collider experiments.

Summary of Main Contributions

The paper introduces several key advancements in version 4 of the code, primarily focusing on enhancing the applicability and reliability of theoretical model testing, which involves Higgs boson masses, branching ratios, production cross sections, and total decay widths as inputs.

1. Updated Algorithm for Exclusion Tests:
   • The core improvement is a modification of the main algorithm to account for significant excesses in experimental data, potentially corresponding to Higgs signals. This adjustment aims to render more consistent and informative exclusion tests even when potential signals are present.
2. Compatibility with LHC Data:
   • The updated code now fully supports testing models against exclusion limits derived from LHC data, at both 7 TeV and 8 TeV center-of-mass energies, thus enhancing the analysis scope across different collider setups.
3. Framework for Theoretical Uncertainty:
   • A novel framework is introduced to incorporate theoretical uncertainties in Higgs mass predictions, addressing a crucial aspect of model predictions that affects the conclusiveness of exclusion limits.
4. Expanded Input Formats:
   • The code's input mechanism is expanded to include options for effective couplings and support for the SLHA format, thereby accommodating a broader range of theoretical models, particularly supersymmetric models.
5. Detailed Output for Model Testing:
   • The output documentation is expanded to provide detailed insights into the exclusion capabilities of individual Higgs bosons within a composite theoretical framework, facilitating more granular analysis.

Implications and Future Directions

The developments presented in this paper have significant implications for both theoretical physics and experimental interpretations:

• Enhanced Theoretical Model Evaluation: By improving the precision and applicability of exclusion tests, the tool becomes more effective in ruling out or supporting theoretical models that predict extended Higgs sectors, thus refining the landscape of viable models in particle physics.
• Greater Synergy with Experimental Data: The integration of LHC-specific exclusion data bridges the gap between ongoing experimental endeavors and theoretical exploration, fostering a more robust dialogue between theory and experiment.
• Tool for Future Colliders: The generalized framework set forth in this version paves the way for adapting the software to future colliders and evolving experimental data, ensuring its relevance and utility in predictive scientific exploration.

Conclusion

The paper represents an increment in the capabilities of computational tools used in high energy physics, particularly concerning the study of the Higgs sector. The updates to the code not only refine the process of testing theoretical predictions with existing exclusion limits but also prepare the groundwork for adapting to new data as it becomes available. This work constitutes an essential resource for researchers working on extensions of the Standard Model and contributes to the evolving understanding of particle physics in the post-Higgs discovery era.