[Paper Review] The Physics Prospects for CLIC

John Ellis|ArXiv.org|Nov 9, 2008

Photonic and Optical Devices3 references3 citations

TL;DR

This paper proposes CLIC, a future $e^+e^-$ collider with a center-of-mass energy of 3 TeV, designed to enable precision measurements beyond the LHC and ILC. Using a two-beam acceleration scheme with 12 GHz RF structures, CLIC achieves high accelerating gradients (80–100 MV/m), enabling luminosities above $10^{34}$ cm$^{-2}$s$^{-1}$, and offers unique capabilities for studying Higgs bosons, supersymmetry, and new physics beyond the Standard Model.

ABSTRACT

Following a brief outline of the CLIC project, this talk summarizes some of the principal motivations for an e+ e- collider with E_CM = 3 TeV. It is shown by several examples that CLIC would represent a significant step beyond the LHC and ILC in its capabilities for precision measurements at high energies. It would make possible a complete study of a light Higgs boson, including rare decay modes, and would provide a unique tool to study a heavy Higgs boson. CLIC could also complete the studies of supersymmetric spectra, if sparticles are relatively light, and discover any heavier sparticles. It would also enable deeper probes of extra dimensions, new gauge bosons and excited quarks or leptons. CLIC has unique value to add to experimental particle physics, whatever the LHC discovers.

Motivation & Objective

• To establish CLIC as a next-generation $e^+e^-$ collider capable of precision measurements at 3 TeV center-of-mass energy.
• To address the limitations of the LHC and ILC by enabling detailed studies of rare Higgs decays and heavy Higgs bosons.
• To explore the full spectrum of supersymmetric particles, including heavier sparticles, if they exist at accessible energies.
• To probe new physics such as extra dimensions, new gauge bosons, and excited quarks or leptons with high sensitivity.
• To demonstrate the feasibility of high-gradient RF acceleration using a two-beam scheme with 12 GHz structures, enabling compact, high-luminosity operation.

Proposed method

• Utilize a two-beam acceleration scheme where a low-energy, high-intensity drive beam generates RF power to accelerate a high-energy, low-intensity main beam.
• Employ 12 GHz accelerating structures (e.g., T18 design) to achieve high accelerating gradients of 80 MV/m (500 GeV option) and 100 MV/m (3 TeV option).
• Implement RF conditioning of structures to reduce breakdown rates to below $3 \times 10^{-7}$ per meter, ensuring stable operation.
• Demonstrate the two-beam acceleration concept in CLIC Test Facility 3 (CTF3), validating key components like RF power generation and beam gymnastics.
• Design the collider layout with a nominal site length of 13.0 km for the 3 TeV option and 48.3 km for the 500 GeV option, based on optimized RF and beam parameters.
• Achieve a nominal luminosity exceeding $10^{34}$ cm$^{-2}$s$^{-1}$ at both 500 GeV and 3 TeV, enabling high-precision measurements.

Experimental results

Research questions

• RQ1 Can a $e^+e^-$ collider at 3 TeV center-of-mass energy provide precision measurements of the Higgs boson beyond the LHC and ILC?
• RQ2 What is the feasibility of achieving accelerating gradients above 80 MV/m in 12 GHz RF structures under realistic operating conditions?
• RQ3 How can a two-beam acceleration scheme enable high luminosity with compact site lengths and high energy reach?
• RQ4 To what extent can CLIC probe new physics beyond the Standard Model, such as supersymmetry, extra dimensions, and excited fermions?
• RQ5 Can the required RF performance and breakdown rates be experimentally demonstrated in prototype structures like T18?

Key findings

• The T18 accelerating structure achieved an accelerating gradient exceeding the nominal CLIC requirement, with a breakdown probability below $3 \times 10^{-7}$ per meter after 1200 hours of RF conditioning.
• The 3 TeV CLIC configuration achieves a luminosity above $10^{34}$ cm$^{-2}$s$^{-1}$, significantly exceeding the ILC and LHC capabilities for precision measurements.
• The 500 GeV CLIC option has a site length of 13.0 km and a luminosity above $10^{34}$ cm$^{-2}$s$^{-1}$, demonstrating a compact, high-performance design.
• The 3 TeV CLIC design has a total site length of 48.3 km, with a nominal accelerating gradient of 100 MV/m, enabling high-energy physics at unprecedented precision.
• The two-beam acceleration scheme, validated in CTF3, enables efficient RF power generation and high-gradient acceleration, forming the core of CLIC’s performance.
• CLIC offers unique sensitivity to rare Higgs decays, heavy Higgs bosons, and new physics such as excited quarks and leptons, complementing LHC and ILC results.