Accurately measuring the properties of the Higgs boson is one of the core physics objectives of the Circular Electron Positron Collider (CEPC). As a Higgs factory, the CEPC is expected to operate at a centre-of-mass energy of $240\,GeV$, deliver an integrated luminosity of $5.6\,ab^{-1}$, and produce one million Higgs bosons according to the CEPC Conceptual Design Report (CDR). Combining measurements of the $\ell^+\ell^-H$, $ν\barν H$, and $q\bar{q}H$ channels, we conclude that the signal strength of $H\to b\bar{b}/c\bar{c}/gg$ can be measured with a relative accuracy (statistic uncertainty only) of 0.27\%/4.03\%/1.56\%. Extrapolating to the recently released TDR operating parameters corresponding to the integrated luminosity of $20\,ab^{-1}$, the relative accuracy of $H\to b\bar{b}/c\bar{c}/gg$ signal strength is 0.14\%/2.13\%/0.82\%. We analyze the dependence of the expected accuracies on the critical detector performances: Color Singlet Identification (CSI) for the $q\bar{q}H$ channel and flavor tagging for both $ν\barν H$ and $q\bar{q}H$ channels. We observe that compared to the baseline CEPC detector performance, ideal flavor tagging increases the $H\to b\bar{b}/c\bar{c}/gg$ signal strength accuracy by 2\%/63\%/13\% in the $ν\barν H$ channel and 35\%/122\%/181\% in the $q\bar{q}H$ channel. In addition, better performance of CSI can significantly improve the anticipated accuracy of signal strength. The relevant systematics are also discussed in this paper.
In November 2018, the CEPC released the Conceptual Design Report (CDR) with the physics potential investigation and the analysis about different detector concepts. Since then, intensive researches on the Higgs Physics at the CEPC have been progressed. The run at top thresholds are also taken into consideration and the physics potential around the center-of-mass energy of 360GeV is studied. The $ttH$ channel information boost the precision of Higgs width measurement by a factor of 2 with respect to 240 GeV Higgs Runs. Different Higgs decay modes are analyzed in the CEPC Higgs factory at the cen…
The Circular Electron Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240-250 GeV. The CEPC will accumulate an integrated luminosity of 5 ab$^{\rm{-1}}$ in ten years' operation, producing one million Higgs bosons via the Higgsstrahlung and vector boson fusion processes. This sample allows a percent or even sub-percent level determination of the Higgs boson couplings. With GEANT4-based full simulation and dedicated fast simulation tool, we evaluated the statistical precisions of the Higgstrah…
In the Circular Electron Positron Collider (CEPC), a measurement of the Higgs CP mixing through $e^{+} e^{-} \rightarrow Z H \rightarrow l^{+} l^{-}(e^{+} e^{-} /μ^{+} μ^{-}) H(\rightarrow b \bar{b} / c \bar{c} / g g)$ process is presented, with $5.6\ \mbox{ab}^{-1}$ $e^{+} e^{-}$ collision data at the center-of-mass energy of $240\ \mathrm{GeV}$. In this study, the CP-violating parameter $\tilde{c}_{Z γ}$ is constrained between the region of $ -0.30$ and $0.27$ and $\tilde{c}_{Z Z}$ between $-0.06$ and $0.06$ at $68\%$ confidence level. This study demonstrates the great potential of probing H…
The Circular Electron-Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240-250 GeV and is expected to accumulate an integrated luminosity of 5 ab$^{\rm{-1}}$ with ten years of operation. At CEPC, Higgs bosons are dominantly produced from $ZH$ associated process. Vast amount of Higgs events collected will enable precise studies of its properties including Yukawa couplings to massive particles. With {\sc GEANT4}-based simulation of detector effects, we study CEPC feasibility on measuring Higgs …
The Circular Electron Positron Collider (CEPC) is a large-scale future collider facility that can serve as a factory of the Higgs boson, the W boson and the Z boson. This document provides a brief summary of the CEPC physics potential and the detector design concepts, both of which are laid out in detail in the Conceptual Design Report (CDR) released in November 2018. We also outline future directions and challenges. In the Addendum, we briefly describe the planning and the international organization of the CEPC. The next step for the CEPC team is to perform detailed technical design studies. …
A strong first-order electroweak phase transition (EWPT) can be induced by light new physics weakly coupled to the Higgs. This study focuses on a scenario in which the first-order EWPT is driven by a light scalar $s$ with a mass between 15-60 GeV. A search for exotic decays of the Higgs boson into a pair of spin-zero particles, $h \to ss$, where the $s$-boson decays into $b$-quarks promptly is presented. The search is performed in events where the Higgs boson is produced in association with a $Z$ boson, giving rise to a signature of two charged leptons (electrons or muons) and multiple jets fr…
In this study, Higgs and Z boson associated production with subsequent decay is attempted in the framework of alternative left-right model, which is motivated by superstring-inspired $E_6$ model at CEPC and future linear colliders. We systematically analyze each decay channel of Higgs with theoretical constraints and latest experimental methods. Due to the mixing of scalars in the Higgs sector, charged Higgs bosons can play an essential role in the phenomenological analysis of this process. Even though the predictions of this model for the signal strengths of this process are close to the stan…
The Circular Electron Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240-250 GeV. The CEPC will accumulate an integrated luminosity of 5 ab$^{\rm{-1}}$ in ten years' operation. With GEANT4-based full simulation samples for CEPC, Higgs boson decaying into electron pair is studied at the CEPC. The upper limit of ${\cal B}(H \rightarrow e^+ e^-)$ could reach 0.024\% at 95\% confidence level. The signal process is generated by MadGraph, with Initial State Radiation (ISR) implemented, as a first…
The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider~(CEPC) is one of such proposed Higgs factories. The CEPC is an $e…
Fast simulation tools are highly appreciated in particle physics phenomenology studies, especially in the exploration of the physics potential of future experimental facilities. The Circular Electron Positron Collider is a proposed Higgs and Z factory that can precisely measure the Higgs boson properties and the electroweak precision observables. A fast-simulation toolkit dedicated to the CEPC detector has been developed using Delphes. The comparison shows that this fast simulation tool is highly consistent with the full simulation, on a set of benchmark distributions. Therefore, we recommend …
The existence of dark matter has been established in astrophysics. However, there is no candidate for DM in the Stand Model (SM). In SM, the Higgs boson can only decay invisibly via $H\rightarrow ZZ^\ast \rightarrow ν\barνν\barν$ or DM, so any evidence of invisible Higgs decay that exceeds BR (H$\rightarrow$inv.) will immediately point to a phenomenon that is beyond the standard model (BSM). In this paper, we report on the upper limit of BR (H$\rightarrow$invisible) estimated for three channels, including two leptonic channels and one hadronic channel, under the assumption predicted by SM. Wit…
As a Higgs factory, The CEPC (Circular Electron-Positron Collider) project aims at the precise measurement of the Higgs boson properties. A baseline detector concept, APODIS (A PFA Oriented Detector for the HIggS factory), has been proposed for the CEPC CDR (Conceptual Design Report) study. We explore the Higgs signatures at this baseline setup with nunuHiggs events. The detector performance of the charged particles, the photons, and the jets are quantified with Higgs -> mumu, gammagamma, and jet final states respectively. The accuracy of reconstructed Higgs boson mass is comparable at differe…
The cross sections of the Higgs production and the corresponding backgrounds of $e^+e^-$ annihilations at the CEPC (Circular Electron and Positron Collider) are calculated by a Monte-Carlo method, and the beamstruhlung effect at the CEPC is carefully investigated. The potential for new physics beyond the Standard Model at the CEPC is discussed.
The Circular Electron Positron Collider (CEPC) is a large international scientific facility proposed by the Chinese particle physics community to explore the Higgs boson and provide critical tests of the underlying fundamental physics principles of the Standard Model that might reveal new physics. The CEPC, to be hosted in China in a circular underground tunnel of approximately 100 km in circumference, is designed to operate as a Higgs factory producing electron-positron collisions with a center-of-mass energy of 240 GeV. The collider will also operate at around 91.2 GeV, as a Z factory, and a…
The associated production of Higgs boson with a muon pair, $e^+e^-\to μ^+μ^- H$, is one of the golden channels to pin down the properties of the Higgs boson in the prospective Higgs factories exemplified by \textsf{CEPC}. The projected accuracy of the corresponding cross section measurement is about per cent level at CEPC. In this work, we investigate both ${\mathcal O}(α)$ weak correction and the ${\mathcal O}(αα_s)$ mixed electroweak-QCD corrections for this channel, appropriately taking into account the effect of finite $Z^0$ width. The $μ^+μ^-$ invariant mass spectrum is also predicted. Th…
The Circular Electron Positron Collider and International Linear Collider are two electron positron Higgs factories. They are designed to operate at center-of-mass energy of 240 and 250 GeV and accumulate 5.6 and 2 $ab^{-1}$ of integrated luminosity. Using CEPC official samples, the signal strength for Higgs to $ττ$ events are analyzed. The combined accuracy of the signal strength for $H\rightarrow ττ$ at CEPC achieves 0.8\%. Extrapolating this analysis to the ILC setup, we conclude the ILC can reach a relative accuracy of 1.1\% or 1.2\%, corresponding to two benchmark settings of the beam pol…
The precision of the yield measurement of the Higgs boson decaying into a pair of $Z$ bosons process at the Circular Electron Positron Collider (CEPC) is evaluated. Including the recoil $Z$ boson associated with the Higgs production (Higgsstrahlung) total three $Z$ bosons are involved for this channel, from which final states characterized by the presence of a pair of leptons, quarks, and neutrinos are chosen for the signal. Two analysis approaches are compared and the final precision of $σ_{\mathrm{ZH}}{\cdot}$BR($H \rightarrow ZZ^{*}$) is estimated to be 7.9% using a multivariate analysis te…
The next-generation lepton colliders, such as CEPC, FCC-ee, and ILC will make precision measurement of the Higgs boson properties. We first extract the Higgs coupling precision from Higgs observables at CEPC to illustrate the potential of future lepton colliders. Depending on the related event rates, the precision can reach percentage level for most couplings. Then, we try to estimate the new physics scales that can be indirectly probed with Higgs and electroweak precision observables. The Higgs observables, together with the existing electroweak precision observables, can probe new physics up…
The rare $b\to sν\barν$ decays are sensitive to contributions of new physics (NP) and helpful to resolve the puzzle of multiple $B$ flavor anomalies. In this work, we propose to study the $b\to sν\barν$ transition at a future lepton collider operating at the $Z$ pole through the $B_s \to ϕν\barν$ decay. Using the $B_s\toϕ$ decay form factors from lattice simulations, we first update the SM prediction of BR($B_s \to ϕν\barν)_{\mathrm{SM}}=(9.93\pm 0.72)\times 10^{-6}$ and the corresponding $ϕ$ longitudinal polarization fraction $F_{L,{\mathrm{SM}}}=0.53\pm 0.04$. Our analysis uses the full CEPC…
This paper presents the prospects of measuring $σ(e^{+}e^{-}\to ZH)\times Br(H \to γγ)$ in 3 $Z$ decay channels $Z \to q\bar{q} / μ^{+} μ^{-} / ν\barν$ using the baseline detector with $\sqrt{s} = 240 GeV$ at the Circular Electron Positron Collider (CEPC) . The simulated Monte Carlo events are generated and scaled to an integrated luminosity of 5.6 $ab^{-1}$ to mimic the data. Extrapolated results to 20 $ab^{-1}$ are also shown. The expected statistical precision of this measurement after combining 3 channels of $Z$ boson decay is 7.7\%. With some preliminary estimation on the systematical unc…
Search potential for direct slepton pair production at the CEPC with $\sqrt{s}$ = 360 GeV
University of the Chinese Academy of Sciences（中国科学院大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；Institute of Physics, Henan Academy of Sciences（河南省科学院物理研究所）；Department of Basic Courses, Naval University of Engineering（海军工程大学基础部）
The Circular Electron Positron Collider (CEPC) with a center-of-mass energy $\sqrt{s}$ = 240 GeV is proposed to serve as a Higgs factory, while it can also provide good opportunity for new physics searches at lower energy, which are difficult in hadron colliders but well-motivated by some theory models such as dark matter. This paper presents the sensitivity study of direct stau / smuon production at CEPC using full Monte Carlo (MC) simulation. With the assumption of flat 5% systematic uncertainty, the CEPC has the potential to discover the production of combined left-handed and right-handed s…
The high-precision measurement of Higgs boson properties is one of the primary goals of the Circular Electron Positron Collider (CEPC). The measurements of $H\to b\bar{b}/c\bar{c}/gg$ decay branching fraction in the CEPC experiment is presented, considering a scenario of analysing 5000 $\mathrm{fb}^{-1}$ $e^{+}e^{-}$ collision data with the center-of-mass energy of 250 GeV. In this study the Higgs bosons are produced in association with a pair of leptons, dominantly mediated by the $ZH$ production process. The statistical uncertainty of the signal cross section is estimated to be about 1 % in …
Now that the mass of the Higgs boson is known, circular electron positron colliders, able to measure the properties of these particles with high accuracy, are receiving considerable attention. Design studies have been launched (i) at CERN with the Future Circular Colliders (FCC), of which an e+e- collider is a potential first step (FCC-ee, formerly caller TLEP) and (ii) in China with the Circular Electron Positron Collider (CEPC). Hosted in a tunnel of at least 50 km (CEPC) or 80-100 km (FCC), both projects can deliver very high luminosity from the Z peak to HZ threshold (CEPC) and even to the…
We study angular observables in the $e^+e^-\to Z H\to \ell^+ \ell^-\,b\bar{b}$ channel at future circular $e^+ e^-$ colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy $\sqrt{s} =$ 240 GeV and 5 (30) ${\rm ab}^{-1}$ integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgs-strahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementa…
We look at the prospects for detecting light bosons, $X$, at proposed Z factories assuming a production of $10^{12}$ Z bosons. Such a large yield is within the design goals of future FCC-ee and CEPC colliders. Specifically we look at the cases where $X$ is either a singlet scalar which mixes with the standard model Higgs or a vector boson with mass $1\lesssim M_X \lesssim 80$ GeV. We find that several channels are particularly promising for discovery prospects. In particular $Z\rightarrow f \bar{f} X$ and $Z \rightarrow V_Q X$ gives a promising signal above a very clean standard model backgrou…
The discovery of a 125 GeV Higgs boson at the LHC marked a breakthrough in particle physics. The relative lightness of the new particle inspires the consideration of a high luminosity Circular Electron Positron Collider (CEPC) as a Higgs Factory to study the Higgs boson in a clean environment. At the CEPC, the beamstrahlung might represent one of the most important sources of beam-induced backgrounds that will impact the detector. It will introduce additional backgrounds to the CEPC detector through the subsequent electron-positron pair production and the hadronic process. Therefore its impact…
The Circular Electron Positron Collider (CEPC) is a proposed Higgs/Z factory. The photon reconstruction is critical to its physics program. We study the photon reconstruction at the CEPC baseline detector, a Particle Flow oriented detector. We characterized the objective performance at both single-photon and di-photon samples. At the single-photon sample, we quantify the photon conversion rate, the differential reconstruction efficiency and energy resolution, and the identification performance. Using di-photon samples, our analysis shows that the CEPC baseline detector reaches a relative mass …
Optimisation of the vertex detector and measurement of Higgs decays to second-generation quarks at the CEPC
National Key Laboratory of Dark Matter Physics, School of Physics and Astronomy, Shanghai Jiao Tong University（暗物质物理全国重点实验室，上海交通大学物理与天文学院）；Key Laboratory for Particle Astrophysics and Cosmology (KLPPAC-MoE), Shanghai Key Laboratory for Particle Physics and Cosmology (SKLPPC)（粒子天体物理与宇宙学教育部重点实验室，上海粒子物理与宇宙学重点实验室）；Laboratoire Leprince-Ringuet, CNRS, Ecole polytechnique, Institut Polytechnique de Paris（勒普林斯-雷格实验室，法国国家科学研究中心，巴黎综合理工学院，巴黎理工学院）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences (UCAS)（中国科学院大学物理科学学院）；National Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University（暗物质物理全国重点实验室，李政道理论与计算科学中心，上海交通大学物理与天文学院）；China Spallation Neutron Source Science Center（中国散裂中子源科学中心）
The design and optimization of the Electromagnetic Calorimeter (ECAL) are crucial for the Circular Electron Positron Collider (CEPC) project, a proposed future Higgs/Z factory. Following the reference design of the International Large Detector (ILD), a set of silicon-tungsten sampling ECAL geometries are implemented into the Geant4 simulation, whose performance is then scanned using Arbor algorithm. At single particle level, the photon energy response at different ECAL longitudinal structures is analyzed. At bi-particle sample, the separation performance with different ECAL transverse cell siz…
After the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider(CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.
Identifying the leptons inside jets is critical for the measurements of Higgs boson and the flavor physics program at the CEPC, a proposed Higgs/Z factory with the main ring circumference of 100 km. Using the CEPC baseline software, we analyze the identification performance of leptons generated inside a jet. The jet leptons are identified with typical efficiency and mis-identification rate of 98% and 1% for energy higher than 2 GeV, with the $Z\to bb$ process at 91.2 GeV center-of mass energy. At the benchmark channel of the CEPC flavor program of $B_{c}\to τν$ with $τ\to eνν$, the electrons a…
The discovery of a SM Higgs boson at the LHC brought about great opportunity to investigate the feasibility of a Circular Electron Positron Collider (CEPC) operating at center-of-mass energy of $\sim 240$ GeV, as a Higgs factory, with designed luminosity of about $2\times 10^{34}cm^{-2}s^{-1}$. The CEPC provides a much cleaner collision environment than the LHC, it is ideally suited for studying the properties of Higgs boson with greater precision. Another advantage of the CEPC over the LHC is that the Higgs boson can be detected through the recoil mass method by only reconstructing Z boson de…
A search for the dimuon decay of the Standard Model Higgs boson is performed using the Monte Carlo simulated events to mimic data corresponding to an integrated luminosity of 5.6 ab$^{-1}$ collected with the Circular Electron-Positron Collider detector in $e^{+}e^{-}$ collisions at $\sqrt{s}=240$ GeV. The paper studies $e^{+}e^{-}\to ZH,\,Z\to q\bar{q},\,H\toμ^{+}μ^{-}$ process, and the expected significance considering only the data statistical uncertainty over the background-only hypothesis for a Higgs boson with a mass of 125 GeV is found to be 6.1$σ$, corresponding to the precision of 19%.…
We investigate the tracker configuration optimization for the Circular Electron Position Collider (CEPC), a proposed Higgs and $Z$ factory. Fixing the construction cost comparable to that of the baseline detector design and considering the benchmark channels ($Z\rightarrow f\bar{f}$, $WW$ fusion with $H\rightarrow f\bar{f}$, $ZH\rightarrowν\barνf\bar{f}$, and $t\bar{t}\rightarrow b\bar{b}μν_μud$) of various operating modes of the CEPC, we obtain the optimal tracker radius that provides the best average resolution of the track momentum or jet energy. The optimal tracker radii for track momentum…
The Circular Electron-Positron Collider (CEPC) can be operated not only as a Higgs factory but also as a Z-boson factory, offering great opportunities for flavor physics studies where Particle Identification (PID) is critical. The baseline detector of the CEPC could record TOF and dE/dx information that can be used to distinguish particles of different species. We quantify the physics requirements and detector performance using physics benchmark analyzes with full simulation. We conclude that at the benchmark TOF performance of $50\,$ps, the dE/dx resolution should be better than 3% for incide…
The scenario of two mass-degenerate Higgs bosons within the general two-Higgs-doublet model (2HDM) is revisited. We focus on the global picture when two $CP$-even Higgs bosons of $h$ and $H$ are nearly mass-degenerate. A global fit to the signal strength of the 125 GeV Higgs measured at the LHC is performed. Based on the best-fit result of the 2HDM mixing angles $(α,β)$, theoretical constraints, charged and $CP$-odd Higgs boson direct search constraints and the electroweak precision constraints are imposed to the 2HDM parameter space. We present the signal predictions of the $(4b\,, 2b\,2γ)$ c…
Due to the high anticipated experimental precision at the Future Circular Collider FCC-ee (or other proposed $e^+e^-$ colliders, such as ILC, CLIC, or CEPC) for electroweak and Higgs-boson precision measurements, theoretical uncertainties may have, if unattended, an important impact on the interpretation of these measurements within the Standard Model (SM), and thus on constraints on new physics. Current theory uncertainties, which would dominate the total uncertainty, need to be strongly reduced through future advances in the calculation of multi-loop radiative corrections together with impro…
LEP precision on electroweak measurements was sufficient not to hamper the extraction of Higgs couplings at the LHC. But the foreseen permille-level Higgs measurements at future lepton colliders might suffer from parametric electroweak uncertainties in the absence of a dedicated electroweak program. We perform a joint, complete and consistent effective-field-theory analysis of Higgs and electroweak processes. The full electroweak-sector dependence of the $e^+e^- \to WW$ production process is notably accounted for, using statistically optimal observables. Up-to-date HL-LHC projections are combi…
Precision study of electroweak symmetry breaking strongly motivates the construction of a lepton collider with center-of-mass energy of at least 240 GeV. Besides Higgsstrahlung ($e^+e^- \to hZ$), such a collider would measure weak boson pair production ($e^+e^- \to WW$) with an astonishing precision. The weak-boson-fusion production process ($e^+e^- \to ν\barν h$) provides an increasingly powerful handle at higher center-of-mass energies. High energies also benefit the associated top-Higgs production ($e^+e^-\to t\bar th$) that is crucial to constrain directly the top Yukawa coupling. The impa…
Following the discovery of the Higgs boson at LHC, new large colliders are being studied by the international high-energy community to explore Higgs physics in detail and new physics beyond the Standard Model. In China, a two-stage circular collider project CEPC-SPPC is proposed, with the first stage CEPC (Circular Electron Positron Collier, a so-called Higgs factory) focused on Higgs physics, and the second stage SPPC (Super Proton-Proton Collider) focused on new physics beyond the Standard Model. This paper discusses this second stage.
Deep-learning jet flavor tagging for precision hadronic Higgs measurements at future $e^+e^-$ Higgs factories
Shanghai Jiao Tong University（上海交通大学）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
A novel perspective on crystal electromagnetic calorimeter design for the CEPC
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；High Energy Research Center, Henan Academy of Sciences（河南省科学院高能研究中心）；Luoyang Mining Machinery Engineering Design Institute CO.,LTD（洛阳矿山机械工程设计研究院有限责任公司）；China Center of Advanced Science and Technology（中国高等科学技术中心）
After the discovery of the Higgs boson, several future experiments have been proposed to study the Higgs boson properties, including two circular lepton colliders, the CEPC and the FCC-ee, and one linear lepton collider, the ILC. We evaluate the precision reach of these colliders in measuring the branching ratios of the charged lepton flavor violating Higgs decays $H\to e^\pmμ^\mp$, $e^\pmτ^\mp$ and $μ^\pmτ^\mp$. The expected upper bounds on the branching ratios given by the circular (linear) colliders are found to be $\mathcal{B}(H\to e^\pmμ^\mp) < 1.2\ (2.1) \times 10^{-5}$, $\mathcal{B}(H\t…
Jet reconstruction is critical for the precision measurement of Higgs boson properties and the electroweak observables at the CEPC. We analyze the jet energy and angular responses of benchmark 2- and 4-jet processes with fully simulated samples with the CEPC baseline detector geometry. We observe a relative resolution of 3.5$\%$ and 1$\%$ on the jet energy and angular measurement for jets in the detector barrel region ($|cosθ| < 0.6$) with energy greater than 60 GeV. Meanwhile, the jet energy/angular scale can be controlled within 0.5/0.01$\%$. The differential dependences of the jet response …
