Beam-spread determination for luminosity measurement at CEPC

Any asymmetry in energy of the colliding beams will lead to a longitudinal boost of the center-of-mass frame of colliding particles w.r.t. the laboratory frame and consequently to the counting loss in luminometer due to the loss of colinearity of Bhabha final states. At CEPC running at the Z0 pole, asymmetry in energy of the colliding beams should be known as well as 12.5% of the beam-spread, in order to control the uncertainty of Bhabha count at the level of 0.01%. Here we discuss the method, initially proposed for FCCee, to determine variation of the beam-spread from the measurement of the effective center-of-mass energy in $e^+e^- \to \mu^+\mu^-$ collisions.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-2

Метод мерења односа гранања Хигсовог бозона BR(H→γγ) на 3 ТеV CLIC

In this thesis is addressed the potential of the Compact Linear Collider (CLIC) operating at 3 TeV center-of-mass energy to measure branching fraction of Higgs boson decay to two photons BR(H→γγ), with 5 ab-1 of integrated luminosity. Since photons are massless, Higgs boson coupling to photons is realized through higher order processes involving the heavy particles either from the Standard Model or beyond. Any deviation of the measured BR(H→γγ) and consequently of the Higgs coupling Hγγ from the predictions of the Standard Model, may indicate New Physics. The Higgs decay to two photons is thus an interesting probe of the Higgs sector at future Higgs factories. The study is performed using the full simulation of а detector for CLIC and by considering relevant physics and beam-induced processes in a full reconstruction chain. Multivariate analysis is employed to separate signal from background, while the shape of the reconstructed di-photon invariant mass distribution is described with the probability density functions (PDFs) for signal and background. Pseudo-data are fitted with PDFs to extract the number of signal events. It is found that, once the Higgs production cross section in WW-fusion is known, BR(H → γγ) can be measured with a relative statistical uncertainty of 5.5% at the confidence level of 68%

Physics potential for the measurement of sigma(H nu antinu ̄) x BR(H -->μ+μ-) at a 1.4 TeV CLIC collider

Measurements of Higgs couplings at CLIC will offer the potential for a rich precision phys- ics programme and for the search for physics beyond the Standard Model(SM). The poten- tial for measuring the SM Higgs boson decay into two muons at a 1.4 TeV CLIC collider is addressed in this paper. The study is performed using a full Geant4 detector simulation of the CLIC_ILD detector model, taking into consideration all the relevant physics and beam-induced background processes, as well as the instrumentation of the very forward region to identify high-energy electrons. In this analysis, we show that the branching ratio BR(H-->μ+μ-) times the Higgs production cross-section in W+W- fusion can be measured with 38% statistical accuracy at sqrt(s) = 1.4 TeV assuming an integrated luminosity of 1.5 ab-1 with unpolarised beams. If 80% electron beam polarisation is considered, as planned for CLIC, the statistical uncertainty of the measurement is 27%. Systematic uncertainties are negligible

International Large Detector: Interim Design Report

The ILD detector is proposed for an electron-positron collider with collision centre-of-mass energies from 90~\GeV~to about 1~\TeV. It has been developed over the last 10 years by an international team of scientists with the goal to design and eventually propose a fully integrated detector, primarily for the International Linear Collider, ILC. In this report the fundamental ideas and concepts behind the ILD detector are discussed and the technologies needed for the realisation of the detector are reviewed. The document starts with a short review of the science goals of the ILC, and how the goals can be achieved today with the detector technologies at hand. After a discussion of the ILC and the environment in which the experiment will take place, the detector is described in more detail, including the status of the development of the technologies foreseen for each subdetector. The integration of the different sub-systems into an integrated detector is discussed, as is the interface between the detector and the collider. This is followed by a concise summary of the benchmarking which has been performed in order to find an optimal balance between performance and cost. To the end the costing methodology used by ILD is presented, and an updated cost estimate for the detector is presented. The report closes with a summary of the current status and of planned future actions

The ILD detector at the ILC

The International Large Detector, ILD, is a detector concept which has been developed for the electron-positron collider ILC. The detector has been optimized for precision physics in a range of energies between 90 GeV and 1 TeV. ILD features a high precision, large volume combined silicon and gaseous tracking system, together with a high granularity calorimeter, all inside a 3.5 T solenoidal magnetic field. The paradigm of particle flow has been the guiding principle of the design of ILD. In this document the required performance of the detector, the proposed implementation and the readiness of the different technologies needed for the implementation are discussed. This is done in the framework of the ILC collider proposal, now under consideration in Japan, and includes site specific aspects needed to build and operate the detector at the proposed ILC site in Japan

The International Linear Collider: Report to Snowmass 2021

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community

The International Linear Collider: Report to Snowmass 2021

International audienceThe International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community

The International Linear Collider: Report to Snowmass 2021

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community