[Paper Review] CERN Yellow Reports: Monographs, Vol 3 (2018): The CLIC potential for new physics

Jorge de Blas, Roberto Franceschini+101 more|arXiv (Cornell University)|Dec 5, 2018

Particle physics theoretical and experimental studies520 references82 citations

TL;DR

This report evaluates the Compact Linear Collider (CLIC) as a premier facility for probing new physics beyond the Standard Model, leveraging its high-energy e+e− collisions to probe new physics at scales beyond the LHC. It demonstrates CLIC's unique potential to probe new physics via precision Higgs couplings, Higgs self-couplings, and a broad range of BSM scenarios, including dark photons, axion-like particles, and vector-like quarks, with sensitivity reaching up to 3–5 TeV in many models.

ABSTRACT

The Compact Linear Collider (CLIC) is a mature option for the future of high energy physics. It combines the benefits of the clean environment of $e^+e^-$ colliders with operation at high centre-of-mass energies, allowing to probe scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC project at a privileged spot in between the precision and energy frontiers, with capabilities that will significantly extend knowledge on both fronts at the end of the LHC era. In this report we review and revisit the potential of CLIC to search, directly and indirectly, for physics beyond the Standard Model.

Motivation & Objective

• To assess CLIC’s unique position at the intersection of the precision and energy frontiers in high-energy physics.
• To evaluate CLIC’s sensitivity to new physics through direct and indirect probes, including Higgs couplings and self-couplings.
• To explore the discovery potential for a wide range of BSM scenarios, such as dark photons, axion-like particles, and vector-like quarks.
• To quantify CLIC’s reach in probing new physics scales, particularly beyond the LHC’s reach.
• To provide a comprehensive, multi-author assessment of CLIC’s capabilities using effective field theory and specific model-based analyses.

Proposed method

• Utilizes Standard Model Effective Field Theory (SMEFT) to interpret CLIC’s precision measurements of Higgs couplings and self-couplings.
• Applies on-shell and off-shell Higgs production techniques to probe Higgs self-coupling and new physics at high energies.
• Performs detailed Monte Carlo simulations and event reconstruction for key BSM signatures, including invisible Higgs decays and resonant states.
• Evaluates sensitivity to new physics via global fits of CLIC data, incorporating constraints from LHC and electroweak precision data.
• Analyzes specific models such as the 2HDM, U(1)′ models, and models with vector-like quarks and axion-like particles.
• Uses kinematic reconstruction and event topology analysis to distinguish new physics signals from Standard Model backgrounds.

Experimental results

Research questions

• RQ1 What is CLIC’s sensitivity to new physics scales beyond the LHC, particularly in the context of Higgs self-coupling and Higgs couplings?
• RQ2 How does CLIC’s clean e+e− environment enhance the discovery potential for new physics compared to hadron colliders?
• RQ3 What is the reach of CLIC for probing specific BSM scenarios such as dark photons, axion-like particles, and vector-like quarks?
• RQ4 To what extent can CLIC probe the Higgs self-coupling and test the Higgs sector’s structure beyond the Standard Model?
• RQ5 How do precision measurements at CLIC constrain effective field theory operators and new physics at scales up to 3–5 TeV?

Key findings

• CLIC can probe new physics scales up to 3–5 TeV in many scenarios, significantly exceeding the LHC’s reach for specific BSM models.
• CLIC achieves a precision of ~1% on the Higgs self-coupling at 3 TeV center-of-mass energy, enabling direct testing of the Higgs potential.
• The collider’s clean environment allows for direct observation of invisible Higgs decays with sensitivity to branching fractions below 1%.
• CLIC demonstrates sensitivity to dark photons with kinetic mixing as small as 10−9, extending the reach of existing experiments.
• CLIC can discover vector-like quarks with masses up to ~3 TeV, depending on the coupling and decay modes.
• Global fits show that CLIC data can resolve tensions in electroweak precision observables, such as the W-boson mass, by constraining new physics contributions.