Measurement of the Higgs Branching Ration BR(H→γγH\rightarrow\gamma\gamma) at 3 TeV CLIC

In this paper we address the potential of a 3 TeV center-of-mass energy Compact Linear Collider (CLIC) to measure the Standard Model (SM) Higgs boson decay to two photons. Since photons are massless, they are not coupled to the Higgs boson at the tree level, but they are created in a loop exchange of heavy particles either from the Standard Model or beyond. Any deviation of the effective $H\rightarrow\gamma\gamma$ branching ratio and consequently of the Higgs to photon coupling may indicate New Physics. The Higgs decay to two photons is thus an interesting probe of the Higgs sector, both at the running and future experiments. A similar study has been performed by C. Grefe at 1.4 TeV CLIC, where the statistical uncertainty is determined to be 15\% for an integrated luminosity of 1.5 $ab^{-1}$ with unpolarized beams. \noindent This study is performed using a full simulation of the detector for CLIC and by considering all relevant physics and beam-induced processes in a full reconstruction chain. The measurement is simulated on 5000 samples of pseudo-experiments and the relative statistical uncertainty is extracted from the pull distribution. It is shown that the Higgs production cross-section in $W^+W^-$ fusion times the branching ratio BR($H\rightarrow\gamma\gamma$) can be measured with a relative statistical accuracy of 8.2\%, assuming an integrated luminosity of 5 $ab^{-1}$ with unpolarized beams

Top-quark physics at the CLIC electron-positron linear collider

Abstract The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies $$\sqrt{s}$$ s = 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of t̄tH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.</jats:p

The Compact Linear Collider (CLIC) - 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years

Measurement of the H to ZZ branching fraction at a 350 GeV and 3 TeV CLIC

In this paper we investigate the prospects for measuring the branching fraction of the Standard Model Higgs boson decay into a pair of Z bosons at the future Compact Linear Collider (CLIC) at 350 GeV and 3 TeV center-of-mass energies. Studies are performed using a detailed simulation of the detector for CLIC, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the Higgs production cross section and the branching fraction BR(H→ZZ*) can be measured with a relative statistical uncertainty of 20% (3.0%) at a center-of-mass energy of 350 GeV (3 TeV) using semileptonic final states, assuming an integrated luminosity of 1  ab-1 (5  ab-1).In this paper we investigate the prospects for measuring the branching fraction of the Standard Model Higgs boson decay into a pair of $Z$ bosons at the future Compact Linear Collider (CLIC) at 350 GeV and 3 TeV centre-of-mass energies. Studies are performed using a detailed simulation of the detector for CLIC, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the Higgs production cross-section and the branching fraction BR(${H\rightarrow\thinspace ZZ^\ast}$) can be measured with a relative statistical uncertainty of 20% (3.0%) at a centre-of-mass energy of 350 GeV (3 TeV) using semileptonic final states, assuming an integrated luminosity of 1 ab$^{-1}$ (5 ab$^{-1}$)

Higgs physics at the CLIC electron-positron linear collider

The Compact Linear Collider (CLIC) is an option for a future e+e− collider operating at centre-of-mass energies up to 3 TeV, providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: √s = 350 GeV, 1.4 and 3 TeV. The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung (e+e− → ZH) and WW-fusion (e+e− → Hνeν¯e), resulting in precise measurements of the production cross sections, the Higgs total decay width ΓH, and model-independent determinations of the Higgs couplings. Operation at √s &gt; 1 TeV provides high-statistics samples of Higgs bosons produced through WW-fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e+e− → t¯tH and e+e− → HHνeν¯e allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit