[Paper Review] Characterizing simplified models for heavy Higgs decays to supersymmetric particles

Suchita Kulkarni, L. Lechner|arXiv (Cornell University)|Oct 31, 2017

Particle physics theoretical and experimental studies117 references4 citations

TL;DR

This paper classifies decay modes of heavy Higgs bosons into supersymmetric particles within the phenomenological MSSM using the SModelS framework, identifying mono-X (X = h, W, Z) final states as dominant for bino- and higgsino-like LSPs, with cross sections up to 10 fb at 14 TeV. It further reveals displaced vertex signatures in wino-like LSP scenarios with large cross sections (~80 fb), emphasizing the need for resonant searches beyond SM final states to probe the full pMSSM parameter space at the high-luminosity LHC.

ABSTRACT

The search for heavy Higgs bosons is an important step to probe the parameter space of the Minimal Supersymmetric Standard Model. In this work, we classify all possible decay modes of the supersymmetric heavy Higgs boson using the SModelS framework. We work within the phenomenological MSSM and use the ATLAS pMSSM study as our viable parameter space. We find that for a bino-like and higgsino-like LSP, a significant region of the parameter space results in mono-$X$ ($X$ = $h$, $W$, $Z$) final states. For wino-like LSPs, we demonstrate the existence of displaced vertex signatures with a large signal cross section. Finally, we argue that by covering the mono-$X$ final states, a large part of heavy Higgs decays can be tested at the LHC.

Motivation & Objective

• To systematically classify decay modes of heavy Higgs bosons into supersymmetric particles within the phenomenological MSSM (pMSSM).
• To identify dominant signatures at the LHC when heavy Higgs bosons decay into supersymmetric final states, especially in regions with large branching ratios to BSM particles.
• To assess the viability of mono-X (X = h, W, Z) and displaced vertex signatures for probing the pMSSM parameter space using current and future LHC data.
• To evaluate the limitations of SM-based Higgs searches in covering the full pMSSM parameter space, especially when BSM decays dominate.
• To demonstrate the utility of the SModelS framework for classifying resonant decays of heavy Higgs bosons to supersymmetric particles.

Proposed method

• Utilizes the SModelS framework to decompose complex pMSSM scenarios into simplified model topologies based on a Z2 symmetry.
• Applies the ATLAS pMSSM study to define a viable, experimentally constrained parameter space for analysis.
• Analyzes decay branching ratios of the heavy CP-even Higgs (H) into neutralino/chargino pairs, with subsequent decays to LSPs and gauge or Higgs bosons.
• Computes production cross sections for pp → H via gluon fusion and bottom-quark annihilation, with subsequent decay to SUSY particles.
• Evaluates signal signatures including mono-jets, mono-bosons (mono-h, mono-W, mono-Z), and displaced vertices, particularly for wino-like LSPs.
• Performs a statistical survey across the 19-dimensional pMSSM parameter space to identify dominant topologies and their cross sections at √s = 14 TeV.

Experimental results

Research questions

• RQ1 Which simplified model topologies dominate the decay of heavy Higgs bosons into supersymmetric particles in the pMSSM?
• RQ2 What are the dominant final states (e.g., mono-X, displaced vertices) for different LSP types (bino-, wino-, higgsino-like) in the viable pMSSM parameter space?
• RQ3 How large are the production and decay cross sections for these dominant signatures at the high-luminosity LHC?
• RQ4 To what extent do current SM-based Higgs searches fail to probe the full pMSSM parameter space when BSM decays dominate?
• RQ5 Can the SModelS framework be effectively extended to classify resonant decays of heavy Higgs bosons to supersymmetric final states?

Key findings

• For bino- and higgsino-like LSPs, mono-X (X = h, W, Z) final states dominate, with production cross sections reaching up to 10 fb at √s = 14 TeV.
• In wino-like LSP scenarios, displaced vertex signatures emerge due to small mass splittings (Δm < 5 GeV) between the light chargino and LSP, with signal cross sections up to 80 fb.
• The dominant production mode for heavy Higgs bosons is bottom-quark annihilation (ttH), accounting for ~98% of the analyzed pMSSM parameter space, leading to associated b-jets in mono-X final states.
• Long-cascade decay signatures are negligible, indicating that heavy Higgs decays to sparticles predominantly result in simple, promptly decaying topologies.
• Direct SM-based Higgs searches are insufficient to probe the full pMSSM parameter space, especially in regions with large BSM branching ratios.
• The study demonstrates that covering mono-X final states would allow testing of a large fraction of heavy Higgs decays to SUSY particles at the LHC.