Application of Multivariate Analysis in Separation of Higgs Boson Signal at future e+e- colliders

Even though the environment at future e+e- colliders is practically QCD background free, there is a large number of processes with high cross-sections and/or similar topology as the Higgs signal of interest. Maximization of the achievable precision of measurements in the Higgs sector and beyond calls for optimized event selection with respect to the statistical significance. This is where the Multivariate Analysis (MVA) is employed, separating the signal from numerous backgrounds on the basis of their kinematic and other properties. In this paper, we discuss the basics of MVA, its application and performance, in examples of several Higgs analyses done in our group using full simulation of the CLIC data.BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S05-HEP High Energy Physics (Particles and Fields

Determination of the CPV Higgs mixing angle in ZZ-fusion at 1.4 TeV CLIC

In this talk we discuss the CP violation in the Higgs sector under assumption that Higgs is a mixture of CP even and odd states. Study is done in ZZ-fusion, at the intermediate energy stage of CLIC, in full simulation of a detector and machine and physics related backgrounds. By measuring kinematic properties of electron and positron in the final state, in the Higgs exlusive decay to bb¯ to reduce backgrounds, we discuss the statistical precision of CP-violating mixing angle measurement with 2.5 ab−1 of data.BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S05-HEP High Energy Physics (Particles and Fields

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 10-4. 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-→μ+μ- collisions.Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-2

Probing CPV mixing in the Higgs sector in VBF at 1 TeV ILC

Although the studies of tensor structure of the Higgs boson interactions with vector bosons and fermions at CMS and ATLAS experiments have established that the JPCquantum numbers of the Higgs boson should be 0++, small CP violation in the Higgs sector (i.e. = 10% contribution of the CP-odd state) cannot be excluded with the current experimental precision. We review a possibility to measure the CP violating mixing angle between scalar and pseudoscalar states of the extended Higgs sector, at 1 TeV ILC with the ILD detector.The European Physical Society Conference on High Energy Physics (EPS-HEP2023) 21-25 August 2023 Hamburg, German

Measurement of the σ x BR(H→ZZ*) at 350 GeV and 3 TeV center-of-mass energies CLIC

In this paper we present results of the determination of the statistical precision of the branching fraction measurement, for Higgs decaying to ∗ pairs at 3 TeV and 350 GeV CLIC. Measurements are simulated with the CLIC_ILD detector model, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the branching fraction ( → ∗ ) and the Higgs production cross-section can be measured with a relative statistical uncertainty of 3% (20%) at 3 TeV (350 GeV) center-of-mass energy, using semileptonic final states and assuming an integrated luminosity of 5 (1) ab−1 .BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S05-HEP High Energy Physics (Particles and Fields

Integrated luminosity measurement at CEPC

The very forward region is one of the most challenging regions to instrument at a future $e^+e^-$ collider. At CEPC, machine-detector interface includes, among others, a calorimeter dedicated for precision measurement of the integrated luminosity at a permille level or better. Here we review a feasibility of such precision, from the point of view of luminometer mechanical precision and positioning, beam-related requirements and physics background.A method of the effective center-of-mass determination from $e^+e^- \to \mu^+\mu^-$, initially proposed for FCC, is also discussed for the CEPC beams.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS2021), 15-18 March 2021. C21-03-15.1. arXiv admin note: text overlap with arXiv:2010.15061, arXiv:2002.0366

Potential and challenges of the physics measurements with very forward detectors at linear colliders

The instrumentation of the very forward region of a detector at a future linear collider (ILC, CLIC) is briefly reviewed. The status of the FCAL R and D activity is given with emphasis on physics and technological challenges. The current status of studies on absolute luminosity measurement, luminosity spectrum reconstruction and high-energy electron identification with the forward calorimeters is given. The impact of FCAL measurements on physics studies is illustrated with an example of the sigma(HWW).BR(H - GT mu(+)mu(-)) measurement at 1.4 TeV CLIC.37th International Conference on High Energy Physics (ICHEP), Jul 02-09, 2014, Valencia, Spai

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.Available at arXiv.org: [https://arxiv.org/abs/2003.01116

Performance and Molière radius measurements using a compact prototype of LumiCal in an electron test beam

A new design of a detector plane of sub-millimetre thickness for an electromagnetic sampling calorimeter is presented. It is intended to be used in the luminometers LumiCal and BeamCal in future linear e+e- collider experiments. The detector planes were produced utilising novel connectivity scheme technologies. They were installed in a compact prototype of the calorimeter and tested at DESY with an electron beam of energy 1–5 GeV. The performance of a prototype of a compact LumiCal comprising eight detector planes was studied. The effective Molière radius at 5 GeV was determined to be (8.1 ± 0.1 (stat) ± 0.3 (syst)) mm, a value well reproduced by the Monte Carlo (MC) simulation (8.4 ± 0.1) mm. The dependence of the effective Molière radius on the electron energy in the range 1–5 GeV was also studied. Good agreement was obtained between data and MC simulation. © 2019, The Author(s)

Measurement of the CPV Higgs mixing angle in ZZ-fusion at 1 TeV ILC

Although the studies of tensor structure of the Higgs boson interactions with vector bosons and fermions at CMS and ATLAS experiments have established that the JPC quantum numbers of the Higgs boson should be 0++, small CP violation in the Higgs sector (up to 10% contribution of the CP-odd state) cannot be excluded with the current experimental precision. We review possibilities to measure CP violating mixing angle ΨCP between scalar and pseudoscalar states, at a linear electron-positron collider, at center-of-mass energy of 1 TeV.2023 International Workshop on Future Linear Colliders, LCWS 2023, May 15-19, Menlo Par