[Paper Review] Searches for Higgs and BSM at the Tevatron

A. Duperrin|arXiv (Cornell University)|Oct 23, 2007

Particle physics theoretical and experimental studies4 citations

TL;DR

This paper presents a comprehensive overview of direct searches for the Standard Model Higgs boson and new physics beyond the Standard Model (BSM) using up to 2 fb⁻¹ of Run II data from the CDF and DØ experiments at Fermilab's Tevatron collider. The analyses, based on multiple final states and advanced multivariate techniques, set stringent limits on Higgs boson masses, supersymmetric particles, leptoquarks, extra gauge bosons, and extra dimensions, with no significant deviations from the Standard Model observed in signature-based searches.

ABSTRACT

This paper presents an overview of recent experimental direct searches for Higgs-boson and beyond-the-standard-model (BSM) physics shown in the plenary session at the SUSY07 conference. The results reported correspond to an integrated luminosity of up to 2 fb-1 of Run II data from $p\bar{p}$ collisions collected by the CDF and D0 experiments at the Fermilab Tevatron Collider. Searches covered include: the standard model (SM) Higgs boson (including sensitivity projections), the minimal supersymmetric extension of the standard model (MSSM), charged Higgs bosons and extended Higgs models, supersymmetric decays that conserve R-parity, gauge-mediated supersymmetric breaking models, long-lived particles, leptoquarks, extra gauge bosons, extra dimensions, and finally signature-based searches. Given the excellent performance of the collider and the continued productivity of the experiments, the Tevatron physics potential looks very promising for discovery in the coming larger data sets. In particular, the Higgs boson could be observed if its mass is light or near 160 GeV.

Motivation & Objective

• To search for the Standard Model Higgs boson and physics beyond the Standard Model (BSM) using high-luminosity proton-antiproton collisions at the Tevatron.
• To probe a broad range of BSM scenarios, including supersymmetry, extended Higgs sectors, long-lived particles, leptoquarks, and extra gauge bosons.
• To set model-independent and model-specific limits on new physics using data-driven background estimation and multivariate analysis techniques.
• To assess the Tevatron's discovery potential for the Higgs boson and new physics with increasing luminosity, especially near 160 GeV.
• To provide a comprehensive summary of experimental results from CDF and DØ for the SUSY2007 conference, informing future physics goals.

Proposed method

• The CDF and DØ experiments analyzed up to 2 fb⁻¹ of integrated luminosity from p¯p collisions at √s = 1.96 TeV.
• Searches employed multivariate analysis techniques, including neural networks, to enhance signal sensitivity across more than 10 final states.
• Backgrounds were estimated using data-driven methods, particularly for multijet and Drell-Yan processes, with validation in control regions.
• Resonance searches for new gauge bosons (Z′, W′) and gravitons used invariant mass reconstruction in di-lepton, di-jet, and photon final states.
• Signature-based searches (Vista and Sleuth) used model-independent and quasi-model-independent approaches to identify deviations from Standard Model predictions.
• Limits were set at 95% confidence level using profile-likelihood methods, with results combined across experiments and final states.

Experimental results

Research questions

• RQ1 What are the current experimental limits on the mass of the Standard Model Higgs boson using Tevatron data with up to 2 fb⁻¹ of integrated luminosity?
• RQ2 Can evidence for supersymmetric particles, such as the lightest neutralino or R-parity-conserving SUSY decays, be observed in the CDF and DØ data?
• RQ3 What are the lower mass limits for new physics states such as leptoquarks, Z′, W′, and excited gravitons in the Tevatron data?
• RQ4 Are there any significant deviations from Standard Model predictions in global signature-based searches for new physics?
• RQ5 How does the Tevatron's performance and luminosity delivery support the discovery potential for the Higgs boson and BSM physics in upcoming data runs?

Key findings

• The Standard Model Higgs boson is excluded at 95% C.L. for masses below 114.4 GeV and above 182 GeV, based on indirect constraints and direct LEP limits.
• For a Higgs boson decaying to b¯b, the observed limit on the signal strength is 2.1 times the Standard Model prediction at 120 GeV.
• CDF and DØ set a lower mass limit of 229 GeV for a Higgs boson decaying into bν, and 251 GeV for vector leptoquarks in τb decay.
• CDF set a lower limit of 923 GeV on the Z′ boson mass assuming SM-like couplings, with lower limits for E6 GUT models.
• For the Randall-Sundrum graviton, CDF and DØ set 95% C.L. upper limits on k/MPlanck as a function of graviton mass, with the strongest constraints in the 1.1–1.3 fb⁻¹ data.
• No significant deviations from the Standard Model were observed in the global signature-based searches (Vista and Sleuth), with all discrepancies within statistical uncertainties.