HiggsBounds 2.0.0: Confronting Neutral and Charged Higgs Sector Predictions with Exclusion Bounds from LEP and the Tevatron

Abstract: HiggsBounds 2.0.0 is a computer code which tests both neutral and charged Higgs sectors of arbitrary models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. HiggsBounds 2.0.0 then uses the expected and observed topological cross section limits from the Higgs searches to determine whether a given parameter scenario of a model is excluded at the 95% C.L. by those searches. Version 2.0.0 represents a significant extension of the code since its first release (1.0.0). It includes now 28/53 LEP/Tevatron Higgs search analyses, compared to the 11/22 in the first release, of which many of the ones from the Tevatron are replaced by updates. As a major extension, the code allows now the predictions for (singly) charged Higgs bosons to be confronted with LEP and Tevatron searches. Furthermore, the newly included analyses contain LEP searches for neutral Higgs bosons (H) decaying invisibly or into (non flavour tagged) hadrons as well as decay-mode independent searches for neutral Higgs bosons, LEP searches via the production modes tau+ tau- H and b b-bar H, and Tevatron searches via t t-bar H. Also, all Tevatron results presented at the ICHEP'10 are included in version 2.0.0. As physics applications of HiggsBounds 2.0.0 we study the allowed Higgs mass range for model scenarios with invisible Higgs decays and we obtain exclusion results for the scalar sector of the Randall-Sundrum model using up-to-date LEP and Tevatron direct search results.

• The paper presents HiggsBounds 2.0.0, which integrates 28 LEP and 53 Tevatron analyses to test both neutral and charged Higgs sectors with 95% confidence.
• It uses a methodology that compares model predictions on Higgs masses, branching ratios, and decay widths with Monte Carlo-derived cross-section limits.
• The tool is applied to evaluate invisible Higgs decays and Randall-Sundrum model constraints, demonstrating its versatility in probing beyond-SM physics.

Insights on the HiggsBounds 2.0.0 Framework for Higgs Sector Exclusion Testing

The paper "HiggsBounds 2.0.0: Confronting Neutral and Charged Higgs Sector Predictions with Exclusion Bounds" presents a sophisticated tool designed to evaluate theoretical models of Higgs sectors against experimental exclusion limits derived from LEP and Tevatron data. This software, HiggsBounds 2.0.0, represents a comprehensive extension from its predecessor, enhancing both its database of analyses and its applicability to new types of Higgs bosons, including charged scalars.

Core Advancements

HiggsBounds 2.0.0 extends the functionality of the original framework by including 28 analyses from LEP and 53 from Tevatron, which is a significant enhancement from the initial 11 and 22 respectively. Importantly, the tool now accommodates scenarios involving charged Higgs bosons—an addition that broadens the spectrum of models that can be tested.

The tool's ability to process models with inputs defined through parameters such as Higgs masses, branching ratios, and decay widths makes it versatile for testing an array of theoretical predictions against established exclusion criteria. The software relies on input formats that allow either detailed or simplified information provision, offering flexibility in terms of computational complexity and accuracy required.

Analytical Strategy

HiggsBounds uses pre-calculated cross-section limits derived from Monte Carlo simulations alongside observed limits to ascertain whether a model is excluded at the 95% confidence level. The code selects the analysis with the highest statistical sensitivity to evaluate a given parameter scenario and compares the model’s predicted exclusion to observed data. Observed and expected limits are key determinants in making exclusion judgments.

An interesting aspect of HiggsBounds 2.0.0 is how it handles overlaid limits from different experimental searches, ensuring a statistically valid exclusion by prioritizing the analyses with the greatest discriminative power for each test case. This methodological rigor ensures that the exclusion results align with the precision of the input data.

Key Applications and Examples

The paper discusses two principal applications of HiggsBounds 2.0.0, reflecting its efficacy and versatility:

1. Invisible Higgs Decays: The tool evaluates parameter spaces in models allowing for invisible Higgs decay scenarios, such as additional decay channels beyond the SM predictions. The study demonstrates that even models with significantly deviating branching ratios for invisible decays can be effectively tested using this tool. The Tevatron analyses, for example, create exclusion zones extending to large branching ratios for invisible channels.
2. Randall-Sundrum Model Constraints: The paper illustrates HiggsBounds's application in probing the scalar sector of the Randall-Sundrum model, identifying exclusion regions based on both LEP and Tevatron results. This serves as the first known application of Tevatron analysis results to such models, emphasizing the tool's pioneering role in drawing theoretical inferences from experimental datasets.

Theoretical and Practical Implications

HiggsBounds 2.0.0 is impactful both practically and theoretically. Practically, it provides physicists with a robust tool to confront their models with contemporary experimental bounds, potentially accelerating the development of beyond-SM physics. Theoretically, it affirms the necessity of refining models to ensure they do not contradict empirical data from high-energy physics experiments.

Future Developments

With the advent of the LHC, subsequent versions of HiggsBounds could incorporate data from even more powerful colliders, thereby refining exclusion criteria and increasing the sensitivity of the Higgs sector analyses. This evolution could stimulate further discoveries or exclusions in unexplored parameter spaces of potential new physics.

The article is a substantive contribution to the field, showcasing a methodical approach to the challenges of constraining theoretical physics models with empirical data, a vital component in the ongoing global effort to understand fundamental particles and forces.