HiggsBounds: Confronting Arbitrary Higgs Sectors with Exclusion Bounds from LEP and the Tevatron

Abstract: HiggsBounds is a computer code that tests theoretical predictions of models with arbitrary Higgs sectors against the exclusion bounds obtained from the Higgs searches at LEP and the Tevatron. The included experimental information comprises exclusion bounds at 95% C.L. on topological cross sections. In order to determine which search topology has the highest exclusion power, the program also includes, for each topology, information from the experiments on the expected exclusion bound, which would have been observed in case of a pure background distribution. Using the predictions of the desired model provided by the user as input, HiggsBounds determines the most sensitive channel and tests whether the considered parameter point is excluded at the 95% C.L. HiggsBounds is available as a Fortran 77 and Fortran 90 code. The code can be invoked as a command line version, a subroutine version and an online version. Examples of exclusion bounds obtained with HiggsBounds are discussed for the Standard Model, for a model with a fourth generation of quarks and leptons and for the Minimal Supersymmetric Standard Model with and without CP-violation. The experimental information on the exclusion bounds currently implemented in HiggsBounds will be updated as new results from the Higgs searches become available.

• The paper introduces HiggsBounds, a computational tool that tests theoretical Higgs models against 95% CL experimental exclusion bounds from LEP and Tevatron.
• It processes detailed inputs such as Higgs masses, decay widths, and cross-section ratios to assess model viability.
• Applications to the Standard Model, Fourth-Generation scenarios, and MSSM benchmarks highlight its effectiveness in delineating allowed parameter spaces.

An Examination of HiggsBounds for Higgs Sector Analysis

The paper, titled "{HiggsBounds}: Confronting Arbitrary Higgs Sectors with Exclusion Bounds from LEP and the Tevatron," introduces a computational tool designed to evaluate the compatibility of theoretical predictions in Higgs sector models with exclusion bounds set by experimental data from LEP and the Tevatron. The tool, HiggsBounds, is crucial in the ongoing development and testing of theoretical models that seek to go beyond the Standard Model (SM).

Core Functionality

HiggsBounds operates by utilizing experimental exclusion limits on topological cross sections obtained from various Higgs searches. These limits are stored as data tables, which the program references to determine whether a given model's predictions are excluded at a 95% confidence level (C.L.). The tool evaluates the most statistically sensitive search topology based on expected exclusion limits and contrasts this with observed data to draw conclusions about model validity.

Input Requirements

Users provide HiggsBounds with detailed theoretical inputs, encompassing Higgs boson masses, decay widths, expected branching ratios, and ratios of production cross sections with respect to reference values. These inputs can be organized in different formats:

• Effective couplings
• Partonic cross section ratios
• Hadronic cross section ratios

HiggsBounds supports processing these inputs both through command-line executions and as an embedded subroutine in larger frameworks, facilitating its integration into comprehensive phenomenological studies.

Application Scope and Results

The paper outlines the application of HiggsBounds to three well-established scenarios: the Standard Model, a Fourth-Generation Model extension, and the MSSM with real and complex parameters. Notably, using HiggsBounds in the Fourth-Generation context emphasizes its utility in demonstrating enhanced exclusion capabilities over the SM, especially in terms of gluon fusion processes.

Additionally, for the MSSM, the tool's flexibility is exhibited across multiple benchmark scenarios, notably the \mhmax, no-mixing, and CPX settings. HiggsBounds aids in charting exclusion regions in parameter spaces such as the $\MA$–$\tb$ plane, crucial for outlining permissible model parameters under current experimental constraints.

Technical and Operational Considerations

The program necessitates accurate theoretical inputs corresponding to the experimental configurations. For instance, ensuring effective coupling parameters mirror their physical processes is critical, as these couplings impact production cross sections and decay channels significantly. Similarly, the narrow-width approximation's assumption underscores the importance of parameter regions where the total widths of potential Higgs signals remain considerably narrower than mass differences.

Implications and Future Research Directions

The development of HiggsBounds addresses a substantial gap in evaluating general Higgs sector models against experimental data, offering an adaptable tool for both theoretical explorations and comparisons with empirical constraints. This functionality is not only pivotal for testing current physics models but also sets the stage for future developments, particularly with anticipated updates to Higgs search results from the LHC.

Looking ahead, advancements such as incorporating width-dependent exclusion limits and expanding the database of experimental results will enhance HiggsBounds' scope and accuracy. Such enhancements would serve a dual purpose: refining theoretical model testing and maintaining the tool's relevance amidst evolving HEP research landscapes.

By offering a clear, systematic approach to Higgs sector exclusions, HiggsBounds continues to be an indispensable asset in the toolkit of physicists probing the frontier of particle physics.