From precision physics to the energy frontier with the Compact Linear Collider

Abstract

The Compact Linear Collider (CLIC) is a proposed high-luminosity collider that would collide electrons with their antiparticles, positrons, at energies ranging from a few hundred Giga-electronvolts (GeV) to a few Tera-electronvolts (TeV). By covering a large energy range and by ultimately reaching multi-TeV e + e − collisions, scientists at CLIC aim to improve the understanding of nature's fundamental building blocks and to discover new particles or other physics phenomena. CLIC is an international project with institutes worldwide participating in the accelerator, detector and physics studies. First e + e − collisions at CLIC are expected around 2035, following the High-Luminosity phase of the Large Hadron Collider at CERN. The article presents an up-to-date overview of the CLIC project for a general audience as presented to the 2020 update of the European Strategy for Particle Physics. * Corresponding author: eva.sicking@cern.ch arXiv:2001.05224v1 [physics.acc-ph] 15 Jan 2020 1 CLIC as the next high-energy collider CLIC as the next high-energy colliderThe discovery of the Higgs boson at the Large Hadron Collider (LHC) in 2012 [1,2] was an important milestone in high-energy physics. It completes a puzzle that scientists have been working on for decades: the Standard Model (SM) of Particle Physics. However it is known that there must be physics Beyond the Standard Model (BSM), for example to account for dark matter and the matter-antimatter asymmetry in the Universe. In the absence of clear guidance towards the scale of BSM physics from the LHC and other experiments to date, plans are already underway to prepare for the next-generation project in high-energy physics.The Compact Linear Collider (CLIC) is a proposed high-luminosity e + e − collider [3][4][5][6]. It is currently the only mature lepton-collider project aiming for multi-TeV energies. CLIC is an international project hosted by CERN with 75 collaborating institutes involved in the accelerator, detector and physics studies. The advantage of CLIC as the next collider is that it gives access to two complementary search paths for new physics. The first path focuses on studying known SM processes with unprecedented precision, to search for deviations from the predicted behaviour. Such deviations would represent indirect evidence of BSM physics. The second path searches for direct production of new particles. The clean environment of e + e − collisions is favourable, both for the detection of even tiny deviations of the expected SM properties and for the detection of rare new signals [5]. Combined, these results from CLIC would provide important guidance for particle physics.The LHC accelerates and collides protons, composite particles made of quarks and gluons, which each carries a varying fraction of the proton's energy. The complex structure of the proton limits knowledge of the individual quarks or gluons de facto participating in the collisions, complicating interpretation of the data. In addition, proton-proton collisions produce vast rates of backgroun...

The Higgs boson implications and prospects for future discoveries

“…The recent European Particle Physics Strategy update 16,17 highlights precision studies of the Higgs boson and its interactions as the main priority for the next high-energy collider. Long-term options past the LHC luminosity upgrade include the Future Circular Collider 200,201 (FCC-ee) or the Compact Linear Collider (CLIC) 202,203 being considered in the context of the future of CERN, with additional electron− positron (e + e − ) collider options being discussed such as the International Linear Collider (ILC) in Japan 204 and the Circular Electron Positron Collider (CEPC) in China 205 . The circular collider projects also include a proton−proton (FCC-hh) and proton−lepton (FCC-eh) option, typically planned as a next stage following the e + e − option.…”

Tau $$g{-}2$$ at $$e^-e^+$$ colliders with momentum-dependent form factor

“…( 17), ( 18) and ( 15), we see that the expected allowed region obtained by the ILC-250 experiment is Fig. 6 The 95% CL upper bounds of a NP τ as functions of the systematic error at the ILC-250, the FCCee-H , and CEPC-H experiments with the designed integrated luminosities of 2.0, 5.0, and 5.6 ab −1 , respectively Table 2 Luminosity sharing between different polarization configurations [64,65] for the CLIC at approximately four times smaller than that obtained from the LEP experiment. After the first stage, the ILC will be operated at √ s = 350 GeV with a smaller integrated luminosity of 0.2 ab −1 .…”

Positron sources: from conventional to advanced accelerator concepts-based colliders

“…In this context, of great importance are also the ongoing feasibility studies on the future multi-TeV 𝜇 + 𝜇 − Muon Collider, which can serve for both precision measurements and discovery physics [3]. These are the future pioneering accelerators of the post-LHC era and the related physics program is extremely ambitious [4][5][6].…”