Physics and Detectors at CLIC: CLIC Conceptual Design Report

TL;DR

The report evaluates the physics potential of a future multi-TeV e+e− collider based on CLIC technology and details two detector concepts (CLIC_ILD and CLIC_SiD) optimized for high-granularity, particle-flow calorimetry. It analyzes the challenging CLIC environment, dominated by beam-induced backgrounds such as incoherent e+e− pairs and gamma-gamma to hadrons, and prescribes stringent timing (∼1–10 ns) and fine segmentation to achieve jet-energy resolutions around 3.5% and superb flavor tagging. Through full detector simulations and six benchmark processes (Higgs, SUSY, heavy Higgs, squarks, charginos/neutralinos, and top-quark physics), the study demonstrates precise mass, width, and cross-section measurements up to √s ≈ 3 TeV and explores implications for dark matter, SUSY-breaking, and extended gauge sectors. It also outlines a robust R&D roadmap for vertex, tracking, calorimetry, magnet, electronics, and detector integration required to realize the CLIC physics program. Overall, the work argues that with carefully designed detectors and timing-capable calorimetry, CLIC can provide complementary, high-precision insights to the LHC, probing Higgs compositeness, SUSY parameter space, extra dimensions, and Z′ scenarios at multi-TeV scales.

Abstract

This report describes the physics potential and experiments at a future multi-TeV e+e- collider based on the Compact Linear Collider (CLIC) technology. The physics scenarios considered include precision measurements of known quantities as well as the discovery potential of physics beyond the Standard Model. The report describes the detector performance required at CLIC, taking into account the interaction point environment and especially beaminduced backgrounds. Two detector concepts, designed around highly granular calorimeters and based on concepts studied for the International Linear Collider (ILC), are described and used to study the physics reach and potential of such a collider. Detector subsystems and the principal engineering challenges are illustrated. The overall performance of these CLIC detector concepts is demonstrated by studies of the performance of individual subdetector systems as well as complete simulation studies of six benchmark physics processes. These full detector simulation and reconstruction studies include beaminduced backgrounds and physics background processes. After optimisation of the detector concepts and adopting the reconstruction algorithms the results show very efficient background rejection and clearly demonstrate the physics potential at CLIC in terms of precision mass and cross section measurements. Finally, an overview of future plans of the CLIC detector and physics study is given and a list of key detector R&D topics needed for detectors at CLIC is presented.

Figures (336)

• Figure 1: Production mechanisms of the SM Higgs boson at CLIC (top); the total cross sections as a function of$M_{\mathrm{H}}$ for $\sqrt{s}=0.5 \mathrm{TeV}$ (middle-left), and 3 TeV (middle-right), and cross sections as a function of $\sqrt{s}$ for $M_{\mathrm{H}}=120 \mathrm{GeV}$ (bottom).
• Figure 2: Relative error in the Higgs boson coupling determination to different particle species. The top diagram is for a Higgs mass of 120 GeV at$\sqrt{s}=500 \mathrm{GeV}$ and with $500 \mathrm{fb}^{-1}$ of integrated luminosity, except $g_{\mathrm{Ht} \mathfrak{t}}$, which is obtained at $\sqrt{s}=800 \mathrm{GeV}$ with $1 \mathrm{ab}^{-1}$. The bottom table gives coupling constant determination and sensitivity to deviations from the SM obtained at CLIC 3 TeV with $2 \mathrm{ab}^{-1}$ for 120 GeV Higgs boson mass (see text for further explanation).
• Figure 3: Reconstructed sample for two Higgs channels with$M_{\mathrm{H}}=120 \mathrm{GeV}$ at CLIC with $\sqrt{s}=3 \mathrm{TeV}$ with $2 \mathrm{ab}^{-1}$. The histograms are stacked distributions of signal and background reconstructed using the CLIC_SiD detector (see Chapter 12).
• Figure 4: Masses and total decay widths of the MSSM Higgs bosons for$\tan \beta=30$ and production cross sections in $\mathrm{e}^{+} \mathrm{e}^{-}$collisions as functions of the masses in $\mathrm{e}^{+} \mathrm{e}^{-}$collisions at $\sqrt{s}=3 \mathrm{TeV}$; from [8].
• Figure 5: Higgs mass peak reconstruction in the processes$\mathrm{e}^{+} \mathrm{e}^{-} \rightarrow \mathrm{HA}$ (left), and in $\mathrm{e}^{+} \mathrm{e}^{-} \rightarrow \mathrm{H}^{+} \mathrm{H}^{-}$ (right), at a CLIC detector using model II, see Section 12.4.3. The corresponding background channels are shown as well. The finite Higgs widths are taken into account.