[Paper Review] Status of Higgs Boson Searches at the Tevatron

A. Sopczak|ArXiv.org|Mar 25, 2009

Particle physics theoretical and experimental studies3 references4 citations

TL;DR

This paper summarizes the status of Higgs boson searches at the Tevatron collider through winter 2008/2009, presenting model-independent and model-dependent limits on Higgs boson masses and couplings using data from CDF and DØ experiments. A key result is the first direct exclusion of a Standard Model Higgs boson in the 160–170 GeV mass range at 95% confidence level, surpassing previous LEP limits and marking a major milestone ahead of the LHC era.

ABSTRACT

Over the last years the Tevatron Run-II has extended several limits on Higgs boson masses and coupling which were pioneered during the LEP accelerator operation between 1989 and 2000. Higgs boson searches will also be at the forefront of research at the LHC. This review concisely discusses the experimental constraints set by the CDF and D0 collaborations in winter 2008/2009 at the beginning of the LHC era. Model-independent and model-dependent limits on Higgs boson masses and couplings have been set and interpretations are discussed both in the Standard Model and in extended models. Recently, for the first time the Tevatron excludes a SM Higgs boson mass range (160-170 GeV) beyond the LEP limit at 95% CL. The experimental sensitivities are estimated for the completion of the Tevatron programme.

Motivation & Objective

• To summarize the experimental constraints on Higgs boson masses and couplings set by the CDF and DØ collaborations at the Tevatron during Run-II.
• To present model-independent and model-dependent limits on Higgs boson production and decay across various final states, including SM and beyond-Standard Model (BSM) scenarios.
• To report the first direct exclusion of a Standard Model Higgs boson in the 160–170 GeV mass range at 95% confidence level, exceeding prior LEP limits.
• To assess the experimental sensitivity of the Tevatron to SM and BSM Higgs bosons through the completion of its program, particularly in the context of upcoming LHC physics.
• To highlight the synergy between phenomenological models and experimental data in interpreting Higgs search results across multiple decay channels.

Proposed method

• Utilized data from proton-antiproton collisions at √s = 1.96 TeV collected by CDF and DØ, with integrated luminosities reaching ~5 fb⁻¹ by winter 2008/09.
• Applied advanced b-quark tagging techniques, including improved impact parameter resolution from vertex detectors (e.g., CDF's L00a layer), to enhance sensitivity to H→bb̄ decays.
• Performed dedicated searches for Higgs boson production via gluon fusion (gg→H→WW), associated production (WH, ZH), and rare decays (H→γγ, H→τ⁺τ⁻, H→tt̄), using optimized kinematic and topological selection criteria.
• Employed statistical methods such as Feldman-Cousins confidence intervals and pseudo-experiment simulations to set upper limits on branching ratios and signal strengths.
• Conducted model-specific searches for charged Higgs (H⁺, H⁺⁺) and fermiophobic Higgs bosons, analyzing final states like H⁺→cs, H⁺⁺→μ⁺μ⁺, and H→γγ.
• Combined results across multiple decay channels and experiments (CDF and DØ) to improve sensitivity and set exclusion limits on Higgs masses and couplings.

Experimental results

Research questions

• RQ1 What are the current experimental limits on the mass and couplings of the Standard Model Higgs boson from Tevatron data collected by winter 2008/09?
• RQ2 Can the Tevatron exclude a Standard Model Higgs boson in the mass range 160–170 GeV, beyond the LEP limit?
• RQ3 How do the sensitivities of CDF and DØ to various Higgs decay modes (e.g., H→bb̄, H→WW, H→γγ) compare, and what improvements have been made since 2005?
• RQ4 What are the constraints on exotic Higgs bosons (e.g., H⁺, H⁺⁺, b̄b̄A) in models beyond the Standard Model?
• RQ5 To what extent do the Tevatron results improve upon LEP limits, and what is the projected sensitivity by the end of Run-II?

Key findings

• The Tevatron achieved the first direct exclusion of a Standard Model Higgs boson in the 160–170 GeV mass range at 95% confidence level, surpassing the previous LEP limit of 114.4 GeV.
• For a 120 GeV SM Higgs boson, approximately 5,000 Higgs bosons were expected to be produced in each experiment with ~5 fb⁻¹ of data, confirming the Tevatron's high production rate.
• The sensitivity to SM Higgs boson searches evolved faster than expected from statistics alone, driven by improved analysis techniques and b-tagging performance.
• CDF and DØ set new limits on the branching ratio of top quark decays to a charged Higgs boson, with observed (expected) limits of BR(t→H⁺b) < 0.35 (0.25) for a 80 GeV H⁺ decaying to cs.
• Limits on fermiophobic Higgs bosons decaying to γγ were set at 95% CL, with CDF excluding masses below ~100 GeV and DØ excluding masses below ~105 GeV for a 4.2 fb⁻¹ dataset.
• Doubly-charged Higgs bosons (H⁺⁺) were excluded up to ~99 GeV at 95% CL, based on di-muon mass spectra and searches for like-sign dilepton final states.