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Physics at the CLIC Multi-TeV Linear Collider

CLIC Physics Working Group, E. Accomando, A. Aranda, E. Ateser, C. Balazs, D. Bardin, T. Barklow, M. Battaglia, W. Beenakker, S. Berge, G. Blair, E. Boos, F. Boudjema, H. Braun, P. Burikham, H. Burkhardt, M. Cacciari, O. Cakir, A. Ciftci, R. Ciftci, B. Cox, C. Da Via, A. Datta, S. De Curtis, A. De Roeck, M. Diehl, A. Djouadi, D. Dominici, J. Ellis, A. Ferrari, J. Forshaw, A. Frey, G. Giudice, R. Godbole, M. Gruwe, G. Guignard, T. Han, S. Heinemeyer, C. Heusch, J. Hewett, S. Jadach, P. Jarron, C. Kenney, Z. Kirca, M. Klasen, K. Kong, M. Kramer, S. Kraml, G. Landsberg, J. Lorenzo Diaz-Cruz, K. Matchev, G. Moortgat-Pick, M. Muhlleitner, O. Nachtmann, F. Nagel, K. Olive, G. Pancheri, L. Pape, S. Parker, M. Piccolo, W. Porod, E. Recepoglu, P. Richardson, T. Riemann, T. Rizzo, M. Ronan, C. Royon, L. Salmi, D. Schulte, R. Settles, T. Sjostrand, M. Spira, S. Sultansoy, V. Telnov, D. Treille, M. Velasco, C. Verzegnassi, G. Weiglein, J. Weng, T. Wengler, A. Werthenbach, G. Wilson, I. Wilson, F. Zimmermann

TL;DR

The paper assesses the physics potential of a multi-TeV $e^+e^-$ linear collider (CLIC) operating from $1$ to $5$ TeV with a luminosity around $10^{35}$ cm$^{-2}$ s$^{-1}$, examining how its unique combination of energy and precision can extend beyond the LHC and lower-energy linear colliders. It presents a comprehensive study of the accelerator complex, including the two-beam drive scheme, high-frequency $30$ GHz cavities, staging to higher energies, and the corresponding detector and background considerations. Its physics program covers Higgs physics (including rare decays, Higgs self-coupling, and CP violation), a complete or expanded SUSY sparticle spectrum accessible to CLIC, and explorations of extra dimensions, new vector resonances, and strong WW scattering, with $ ext{γγ}$ and polarization modes providing additional handles. The study argues that CLIC’s high energy and precision enable detailed, beyond-LHC measurements—such as heavy Higgs properties, precise sparticle mass and coupling determinations, and sensitivity to new dynamics—thereby offering significant advances in our understanding of electroweak symmetry breaking and TeV-scale physics.

Abstract

This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, γγand e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: γγcollisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model, such as theories with extra dimensions or new vector resonances, new contact interactions and models with strong WW scattering at high energies. In all the scenarios we have studied, CLIC would provide significant fundamental physics information beyond that available from the LHC and a lower-energy linear e+e- collider, as a result of its unique combination of high energy and experimental precision.

Physics at the CLIC Multi-TeV Linear Collider

TL;DR

The paper assesses the physics potential of a multi-TeV linear collider (CLIC) operating from to TeV with a luminosity around cm s, examining how its unique combination of energy and precision can extend beyond the LHC and lower-energy linear colliders. It presents a comprehensive study of the accelerator complex, including the two-beam drive scheme, high-frequency GHz cavities, staging to higher energies, and the corresponding detector and background considerations. Its physics program covers Higgs physics (including rare decays, Higgs self-coupling, and CP violation), a complete or expanded SUSY sparticle spectrum accessible to CLIC, and explorations of extra dimensions, new vector resonances, and strong WW scattering, with and polarization modes providing additional handles. The study argues that CLIC’s high energy and precision enable detailed, beyond-LHC measurements—such as heavy Higgs properties, precise sparticle mass and coupling determinations, and sensitivity to new dynamics—thereby offering significant advances in our understanding of electroweak symmetry breaking and TeV-scale physics.

Abstract

This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, γγand e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: γγcollisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model, such as theories with extra dimensions or new vector resonances, new contact interactions and models with strong WW scattering at high energies. In all the scenarios we have studied, CLIC would provide significant fundamental physics information beyond that available from the LHC and a lower-energy linear e+e- collider, as a result of its unique combination of high energy and experimental precision.

Paper Structure

This paper contains 5 sections, 2 equations, 5 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. ACCELERATOR ISSUES AND PARAMETERS
  3. Overview of the CLIC Complex
  4. CLIC Energy and RF Technology Choice
  5. CLIC Luminosity

Figures (5)

  • Figure 1: Bar charts of the numbers of different sparticle species observable in a number of benchmark supersymmetric scenarios at different colliders, including the LHC and linear $e^+ e^-$ colliders with various centre-of-mass energies. The benchmark scenarios are ordered by their consistency with the most recent BNL measurement of $g_\mu - 2$ and are compatible with the WMAP data on cold dark matter density. We see that there are some scenarios where the LHC discovers only the lightest neutral supersymmetric Higgs boson. Lower-energy linear $e^+ e^-$ colliders largely complement the LHC by discovering or measuring better the lighter electroweakly-interacting sparticles. Detailed measurements of the squarks would, in many cases, be possible only at CLIC.
  • Figure 2: An example of the dilepton spectrum that might be observed at the LHC in some scenario for extra dimensions, including Kaluza--Klein excitations of the photon and $Z$ and their interferences.
  • Figure 3: The schematics of the overall layout of the CLIC complex
  • Figure 4: Macro-photographs of the input coupler of a 30 GHz RF copper structure, showing the erosion damage subsequent to breakdown in RF tests
  • Figure 5: Accelerating gradients obtained with 30 GHz structures of different designs. The gradient measured in the first cell of the structure is shown as a function of the number of applied RF pulses.