[Paper Review] A CLIC-Prototype Higgs Factory

R. Belusević, T. Higo|arXiv (Cornell University)|Aug 24, 2012

Particle Accelerators and Free-Electron Lasers6 references3 citations

TL;DR

This paper proposes a compact, high-gradient X-band linear collider based on CLIC technology to serve as an $e^{+}e^{-}/\gamma\gamma$ Higgs factory, enabling precise measurements of the Higgs boson's mass, spin, parity, couplings, and self-coupling through multiple final states. The facility achieves higher luminosity and lower required center-of-mass energy than TESLA-type designs, with photon production via Compton scattering from an optical FEL, enabling high-precision electroweak studies and Higgs self-coupling detection.

ABSTRACT

We propose that a pair of electron linacs with high accelerating gradients and an optical FEL be built at an existing laboratory. The linacs would employ CLIC-type rf cavities and a klystron-based power source; a two-beam scheme could be implemented at a later stage. The proposed facility would serve primarily as an e+e-/gamma-gamma Higgs-boson factory. The rich set of final states in e+e- and gamma-gamma collisions would play an essential role in measuring the mass, spin, parity, two-photon width and trilinear self-coupling of the Higgs-boson, as well as its couplings to fermions and gauge bosons. These quantities are more difficult to determine with only one initial state. For some processes within and beyond the Standard Model, the required CM energy is considerably lower at the proposed facility than at an e+e- or proton collider.

Motivation & Objective

• To design a high-luminosity, compact $e^{+}e^{-}/\gamma\gamma$ collider for precision Higgs boson studies.
• To overcome limitations of TESLA-type designs, including low accelerating gradients, long damping rings, and cryogenic complexity.
• To enable direct measurement of the Higgs boson's trilinear self-coupling and couplings to fermions and gauge bosons through multiple initial states.
• To develop a prototype for a future TeV-scale, high-gradient linear collider based on CLIC technology.
• To reduce construction costs and technical challenges by reusing the same interaction region and beam dump for both $e^{+}e^{-}$ and $\gamma\gamma$ modes.

Proposed method

• Utilize CLIC-type X-band RF cavities with high accelerating gradients and klystron-based power sources to achieve compact, high-gradient electron linacs.
• Implement a two-beam drive scheme at a later stage to enhance RF power efficiency.
• Generate high-energy photons via Compton scattering of laser pulses on relativistic electron beams using an optical free electron laser (FEL).
• Employ electron and positron damping rings in a single tunnel to minimize footprint and cost, with a switchable positron source for $e^{+}e^{-}$ operation.
• Design the interaction region with a crab-crossing scheme to mitigate beam-beam effects and enable efficient beam removal.
• Use a single beam dump and crossing angle for both $e^{+}e^{-}$ and $\gamma\gamma$ collision modes to reduce construction and operational costs.

Experimental results

Research questions

• RQ1 Can a high-gradient X-band linear collider based on CLIC technology achieve sufficient luminosity to measure the Higgs boson's trilinear self-coupling with high precision?
• RQ2 How does the $e^{+}e^{-}/\gamma\gamma$ collider mode compare to TESLA-type designs in terms of luminosity, cost, and technical feasibility?
• RQ3 What is the optimal configuration for a photon collider using Compton scattering from an optical FEL to produce polarized photons for Higgs studies?
• RQ4 To what extent can the same interaction region and beam dump be used for both $e^{+}e^{-}$ and $\gamma\gamma$ collision modes to reduce costs?
• RQ5 Can the proposed facility serve as a prototype for a future TeV-scale, high-gradient linear collider such as CLIC?

Key findings

• The proposed $e^{+}e^{-}/\gamma\gamma$ collider can achieve a geometric luminosity of approximately $5 \times 10^{33}$ cm⁻²s⁻¹ at the Z resonance, yielding about $2 \times 10^9$ Z bosons per year—200 times more than LEP.
• The facility enables a $10^6$ W-boson production rate near the W-pair threshold, significantly improving W-boson mass measurement precision.
• Luminosity in $\gamma\gamma$ collisions can, in principle, exceed that of $e^{+}e^{-}$ collisions if beams with minimal emittance and strong horizontal focusing are used.
• The use of X-band linacs allows for shorter damping rings and lower RF power requirements for laser pulses compared to TESLA-type S-band systems.
• The facility can serve as a prototype for a future TeV-scale, high-gradient linear collider, unlike TESLA-type designs which lack this scalability.
• The crab-crossing scheme effectively mitigates beam-beam effects from Compton-scattered electrons, enabling efficient beam cleaning and high-performance operation.