ALPs effective field theory and collider signatures

Area of Science:

• Particle Physics
• High Energy Physics
• Theoretical Physics

Background:

• The Standard Model (SM) describes fundamental particles and forces, but doesn't explain phenomena like dark matter or electroweak symmetry breaking.
• Exploring physics beyond the Standard Model (BSM) is crucial for a complete understanding of the universe.
• Goldstone bosons, arising from spontaneous symmetry breaking, are key theoretical constructs in BSM physics.

Purpose of the Study:

• To investigate the effective interactions between SM fields and a generic singlet CP-odd (pseudo-) Goldstone boson.
• To compare linear and non-linear electroweak symmetry breaking frameworks for these interactions.
• To identify and analyze phenomenological signals at particle colliders, setting new experimental bounds.

Main Methods:

• Formulation of effective field theories for linear and non-linear electroweak symmetry breaking scenarios.
• Determination of the basis of leading effective operators for the non-linear case.
• Analysis of collider signatures including mono-Z, mono-W, W-photon plus missing energy, on-shell top production, and Higgs boson decays.

Main Results:

• Identified mono-Z, mono-W, W-photon plus missing energy, and on-shell top final states as promising signals in both linear and non-linear frameworks.
• Established new experimental bounds on the parameters of the considered BSM scenarios.
• Highlighted non-standard Higgs decays and mono-Higgs signatures as particularly significant for non-linear realisations.

Conclusions:

• The study provides a comprehensive analysis of a specific BSM scenario involving a CP-odd Goldstone boson.
• Collider experiments, particularly at the Large Hadron Collider (LHC) and High Luminosity LHC (HL-LHC), offer promising avenues for discovering such new physics.
• The identified signals and derived bounds will guide future experimental searches for physics beyond the Standard Model.