[Paper Review] Introducing HiggsBounds 2.0.0

P. Bechtle, Oliver Brein+3 more|arXiv (Cornell University)|Dec 23, 2010

Particle physics theoretical and experimental studies2 references3 citations

TL;DR

HiggsBounds 2.0.0 is a model-independent tool that tests arbitrary Higgs sectors against LEP and Tevatron exclusion limits using predicted Higgs masses, branching ratios, couplings, and cross sections. It determines whether a given model scenario is excluded at 95% confidence level by comparing model predictions to observed and expected cross-section limits from 39/53 Higgs search analyses, significantly expanding coverage over previous versions and enabling robust exclusion testing for models like the 4th generation, MSSM, and Randall-Sundrum scenarios.

ABSTRACT

We introduce version 2.0.0 of the computer program HiggsBounds. The program tests neutral and charged Higgs sectors of new models against the current exclusion bounds from 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. The program 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 includes 39/53 LEP/Tevatron Higgs search analyses, compared to 13/36 in the previous release (1.2.0). Among the newly included analyses are LEP searches for neutral Higgs bosons (H) decaying invisibly or into hadrons, LEP searches via the production modes (tau+ tau- H) and (b b-bar H), Tevatron searches via (t t-bar H), and LEP and Tevatron searches for charged Higgs bosons. Also, all Tevatron results presented at the ICHEP'10 are included in version 2.0.0. In this talk, we explain the basic ideas behind the implementation of HiggsBounds and provide a list of search topologies implemented in version 2.0.0. Furthermore, we apply HiggsBounds 2.0.0 to (a) determine the allowed Higgs mass range for a simple 4th generation model, (b) update/reproduce LEP/Tevatron Higgs exclusion plots for the MSSM m_h-max benchmark scenario, and (c) show exclusion results for the scalar sector of the Randall-Sundrum model.

Motivation & Objective

• To provide a model-independent tool for testing arbitrary Higgs sectors against experimental exclusion bounds from LEP and Tevatron Higgs searches.
• To extend the coverage of Higgs exclusion analyses in HiggsBounds, including new LEP and Tevatron search topologies such as invisible decays, $b\bar{b}H$, $\tau^+\tau^-H$, $t\bar{t}H$, and charged Higgs searches.
• To enable researchers to determine whether a given model parameter scenario is excluded at 95% confidence level by comparing predicted signal cross sections to observed and expected limits.
• To support updated and reproducible exclusion plots for benchmark models such as the MSSM $m_h^{\text{max}}$ scenario and the scalar sector of the Randall-Sundrum model.

Proposed method

• The program takes model predictions as input: Higgs masses, total widths, branching ratios, and production cross section ratios relative to reference values.
• It evaluates all implemented LEP and Tevatron Higgs search analyses to determine if they are applicable to the given model scenario.
• For each applicable analysis, it compares the model's predicted signal cross section (scaled by branching ratios) to the observed and expected exclusion limits at 95% C.L.
• Exclusion is claimed only if the model's predicted cross section exceeds the observed limit in the most sensitive analysis, preserving statistical confidence level.
• The tool is available via command line, Fortran subroutines (77/90), and a web interface, ensuring broad accessibility.
• It uses Monte Carlo simulations to determine expected limits, which are used to assess statistical sensitivity and avoid over-interpretation of exclusion claims.

Experimental results

Research questions

• RQ1 Can HiggsBounds 2.0.0 accurately determine whether a given Higgs model is excluded at 95% C.L. by LEP and Tevatron data?
• RQ2 How does the inclusion of 39/53 new Higgs search analyses in version 2.0.0 improve the sensitivity and coverage compared to version 1.2.0?
• RQ3 To what extent can HiggsBounds 2.0.0 reproduce or update existing exclusion plots for benchmark models like the MSSM $m_h^{\text{max}}$ scenario?
• RQ4 How does the program handle non-SM-like models where signal cross sections do not scale uniformly with the SM?
• RQ5 What are the implications of HiggsBounds 2.0.0 for models with extended Higgs sectors, such as the 4th generation model or the Randall-Sundrum scalar sector?

Key findings

• HiggsBounds 2.0.0 includes 39 out of 53 LEP and Tevatron Higgs search analyses, a significant increase from 13/36 in version 1.2.0, including key analyses such as LEP searches for $H \to \text{invisible}$, $H \to b\bar{b}$, $\tau^+\tau^-H$, and Tevatron $t\bar{t}H$ and charged Higgs searches.
• The program successfully reproduces LEP exclusion plots for the MSSM $m_h^{\text{max}}$ benchmark scenario, showing good agreement with published results using updated predictions from FeynHiggs 2.7.1.
• For the 4th generation model, HiggsBounds 2.0.0 confirms a Tevatron exclusion range of 130–220 GeV for the Higgs boson, consistent with previous studies.
• In the MSSM $m_h^{\text{max}}$ scenario, the inclusion of all ICHEP'10 Tevatron results in HiggsBounds 2.0.0 reveals a gap in exclusion for $200\,\text{GeV} < m_A < 220\,\text{GeV}$, suggesting potential for future coverage if the $\tau\tau$ analysis were extended.
• For the Randall-Sundrum model (RS1), HiggsBounds 2.0.0 identifies the $\gamma\gamma$ and $b\bar{b}$ channels as most sensitive for the radion-like state $\varphi$ at low masses, while the SM-like Higgs $h$ is excluded in a region consistent with its couplings.
• The tool demonstrates that HiggsBounds 2.0.0 correctly identifies the most sensitive analysis for each model point, ensuring that exclusion claims are statistically valid and preserve the 95% C.L. requirement.