Forward calorimetry at ILC

The very forward region of a detector at the International Linear Collider (ILC) is particularly challenging area for instrumentation. Forward calorimeters should provide luminosity measurement with the high precision, tuning of the beam parameters, detector hermeticity at lowest polar angles and shielding of the central detectors from backscattered particles. High-energy electron identification is particularly important to veto Standard Model background to new particle searches. In addition, extreme radiation hardness in required for the innermost calorimeter due to several tens of TeV depositions of beamstrahlung remnants per bunch crossing

Systematic effects in luminosity measurement at ILC

In order to achieve required precision of luminosity measurement at the International Linear Collider (ILC), that is of order of 10-4, systematic effects have to be understood at the level of this precision. Apart from systematic effects originating from hardware design and precision of the detector alignment, physics processes also contribute either as a background or additional interaction effects. Properties of physics background, its separation from the Bhabha signal, as well as the influence of selection criteria on the overall systematics of the measurement have been studied

A compact fine-grained calorimeter for luminosity measurement at a linear collider

Based on a paper published in 2019 by the FCAL Collaboration, this talk is giving an update of the Collaboration's effort to design prototype of highly compact calorimeter to instrument the very forward region of a detector at future e+e- colliders. A luminometer prototype, based on sub-millimeter thick detector planes, is tested with an electron-beam of energy 1-5 GeV. The effective Molière radius of the prototype comprising eight detector planes was measured to be (8.1 ± 0.1 (stat) ± 0.3 (syst)) mm, and the result is well reproduced by the Monte Carlo simulation.Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-2

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

CLIC is a mature project for a future staged e-e+ linear collider at CERN. It is designed to run at three different energy stages currently assumed to be 380 GeV, 1.5 TeV and 3 TeV. Staged energy approach enables exploring precision Higgs and top physics as well as the possibility for direct and indirect BSM searches. In this paper we present an overview of the Higgs physics together with preliminary results of the CPV study in ZZ-fusion at the intermediate energy stage.On behalf of the CLICdp Collaboration41st International Conference on High Energy physics - ICHEP2022; 6-13 July, 2022; Bologna, Ital

Measurement of the Higgs decay to electroweak bosons at low and intermediate CLIC energies

In this paper a simulation of measurements of the Higgs boson decay to electroweak bosons in $e^+e^-$ collisions at CLIC is presented. Higgs boson production and subsequent $H\rightarrow ZZ^\ast$ and $H\rightarrow WW^\ast$ decay processes were simulated alongside the relevant background processes at 350 GeV and 1.4 TeV center-of-mass energy. Full detector simulation and event reconstruction were used under realistic beam conditions. The achievable statistical precision of the measured product of the Higgs production cross section and the branching ratio for the analysed decays has been determined.Comment: Talk presented at International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 2015, CLICdp-Conf-2016-00

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

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

Measurement of σ(HVeVe) x BR(H→ ZZ*) and Higgs production in ZZ fusion at a 1.4 TeV CLIC collider

This paper presents the potential measurement at 1.4 TeV CLIC of the cross-section (times branching ratio) of the Higgs production via WW fusion with the Higgs subsequently decaying in ZZ⇤, s(Hnen¯e)⇥BR(H ! ZZ⇤), and of the Higgs production via ZZ fusion with the Higgs subsequently decaying in bb¯, s(He+e)⇥BR(H ! bb¯). For the H ! ZZ⇤ decay the hadronic final state, ZZ⇤ ! qqq¯ q¯, and the semi-leptonic final state, ZZ⇤ ! qql¯ +l , are considered. The results show that s(Hnen¯e)⇥BR(H ! ZZ⇤) can be measured with a precision of 18.3% and 6% for the hadronic and semi-leptonic channel, respectively. s(He+e)⇥BR(H ! bb¯) can be measured with a precision of 1.7%. This measurement also contributes to the determination of the Higgs coupling to the Z boson, gHZZInternational Workshop on Future Linear Colliders (LCWS14) : October 6-10, Belgrade, 2014