[Paper Review] CMS Higgs physics results

M. Flechl|arXiv (Cornell University)|May 17, 2019

Particle physics theoretical and experimental studies2 references4 citations

TL;DR

This paper presents updated CMS searches for rare and beyond-Standard Model Higgs boson decays and additional Higgs states, using LHC Run 2 data. Key results include a combined limit of B(H → inv) < 0.19, improved sensitivity to H → ΥΥ and H → aa decays, and new exclusion limits for heavy Higgs bosons in multiple final states, all consistent with the Standard Model but probing new physics scenarios.

ABSTRACT

Recent results of searches for Higgs bosons by the CMS collaboration are presented. These consist of searches for rare Higgs boson decays, searches for additional neutral Higgs bosons, and searches for charged Higgs bosons.

Motivation & Objective

• To test the Standard Model Higgs boson hypothesis by searching for rare decay modes not predicted at significant branching ratios.
• To probe new physics scenarios, including dark matter portals, 2HDM, NMSSM, and MSSM, through searches for additional neutral and charged Higgs bosons.
• To improve sensitivity to exotic Higgs decays by analyzing new final states and leveraging advanced reconstruction techniques.
• To set exclusion limits on Higgs boson decays to invisible particles, mesons, light pseudoscalars, and heavy Higgs bosons in multiple production and decay channels.
• To enhance sensitivity beyond pure luminosity scaling through optimized analysis techniques and machine learning in challenging topologies.

Proposed method

• Reinterpretation of ttH topology searches using 0-, 1-, and 2-lepton final states to set bounds on H → invisible decays.
• Combination of gluon fusion, vector boson fusion, and V-associated production analyses across LHC Run 1 and Run 2 data to improve sensitivity to H → invisible decays.
• Use of dedicated 2- and 3-muon triggers with mass windows to enhance sensitivity to H → J/ψJ/ψ and H → ΥΥ decays.
• Application of matrix-element-based estimators (SVFit) and kinematic reconstruction to identify Higgs bosons decaying to Zh in the A → Zh channel.
• Employment of machine learning algorithms to classify events in high-multiplicity final states for H⁺ → tb and H⁺ → AW searches.
• Combination of multiple final states—τ + jets, τ + 1 lepton, τ + 0 lepton—for H⁺ → τν across low, intermediate, and high mass regions.

Experimental results

Research questions

• RQ1 What is the current limit on the branching ratio for Higgs boson decays to invisible particles, and how does it compare to SM predictions?
• RQ2 Can new physics be probed through rare Higgs decays to mesons such as J/ψJ/ψ or ΥΥ, given their high sensitivity and low background?
• RQ3 How does the CMS collaboration improve sensitivity to light pseudoscalar decays (H → aa) in the 4–15 GeV mass range, especially in boosted topologies?
• RQ4 What are the exclusion limits for heavy neutral Higgs bosons decaying to top quark pairs or Zh in the MSSM and hMSSM scenarios?
• RQ5 What are the constraints on charged Higgs boson decays to τν, tb, and AW across a wide mass range in the MSSM framework?

Key findings

• The combined limit on Higgs boson decays to invisible particles is B(H → inv) < 0.19 (expected: 0.15), representing the current best constraint.
• The limit on H → J/ψJ/ψ is B(H → J/ψJ/ψ) < 1.8 × 10⁻³, and on H → ΥΥ is B(H → ΥΥ) < 1.4 × 10⁻³, both with expected significance.
• For H → aa decays with a₁ mass between 4 and 15 GeV, the limit improves from ~25% to ~3% at mₐ = 8 GeV, exceeding pure luminosity scaling.
• A local 3.8σ excess in the ttH topology is observed at a Higgs boson mass of 400 GeV, though the global significance is only 2σ, indicating no discovery.
• Exclusion limits for H⁺ → τν are set across the mass range of 80 GeV to 3000 GeV, with strong sensitivity in the intermediate mass region for the first time in CMS.
• For H⁺ → AW decays, limits on the branching ratio t → bH⁺ range from 0.6% to 2.9% for A boson masses from 15 GeV to 75 GeV, with a focus on dimuon final states.