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Measurements of decay branching fractions of H→b■/c■/gg in associated (e^+e^-/μ^+μ^-)H production at the cepc

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Chinese Physics C 2020年第1期44卷 1-10页

作者：白羽陈春晖方亚泉李刚阮曼奇史静远王博孔攀宇兰博扬刘站峰 School of Physics Southeast UniversityNanjing 210096China Department of Physics and Astronomy Iowa State UniversityAmes 50011-3160USA Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China School of physics and astronomy the University of ManchesterOxford RdM139PLUK Department of Physics College of SciencesNortheastern UniversityShenyang 110004China School of Cyber Science and Engineering Southeast UniversityNanjing 210096China

The high-precision measurement of Higgs boson properties is one of the primary goals of the Circular Electron Positron Collider(cepc).The measurements ofH→bb/cc/gg decay branching fraction in the cepc experiment is presented,considering a scenario of analysing 5000 fb-1 e^+e^-collision data with the center-of-mass energy of 250 Ge V.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 theH→bb final state,and approximately 5%-10%in theH→cc/gg final states.In addition,the main sources of the systematic uncertainties and their impacts to the measurements of branching fractions are discussed.This study demonstrates the potential of precise measurement of the hadronic final states of the Higgs boson decay at the cepc,and will provide key information to understand the Yukawa couplings between the Higgs boson and quarks,which are predicted to be the origin of quarks’masses in the standard model.

关键词： the Higgs boson cepc branching fraction flavor tagging

An optimal scheme for top quark mass measurement near the t threshold at future e^+e^- colliders

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Chinese Physics C 2018年第5期42卷 16-24页

作者：陈卫国万霞王由凯 School of Physics&Information Technology Shaanxi Normal UniversityXi'an 710119China

A top quark mass measurement scheme near the t production threshold in future e~+e~- colliders, e.g. the Circular Electron Positron Collider(cepc), is simulated. A χ~2 fitting method is adopted to determine the number of energy points to be taken and their locations. Our results show that the optimal energy point is located near the largest slope of the cross section v. beam energy plot, and the most efficient scheme is to concentrate all luminosity on this single energy point in the case of one-parameter top mass fitting. This suggests that the so-called data-driven method could be the best choice for future real experimental measurements. Conveniently, the top mass statistical uncertainty can also be calculated directly by the error matrix even without any sampling and fitting. The agreement of the above two optimization methods has been checked. Our conclusion is that by taking 50 fb-1total effective integrated luminosity data, the statistical uncertainty of the top potential subtracted mass can be suppressed to about 7 Me V and the total uncertainty is about 30 Me V. This precision will help to identify the stability of the electroweak vacuum at the Planck scale.

关键词： cepc top mass threshold scan

Precision Higgs physics at the cepc

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Chinese Physics C 2019年第4期43卷 5-44页

作者：安芬芬白羽陈春晖陈新陈振兴 Joao Guimaraes da Costa 崔振崴方亚泉付成栋高俊高艳彦高原宁葛韶锋顾嘉荫郭方毅郭军韩涛韩爽何红建何显柯何小刚胡继峰徐士杰金山荆茂强 Susmita Jyotishmati Ryuta Kiuchi 郭家铭赖培筑李博扬李聪乔李刚李海峰李亮李数李通李强梁浩梁志均廖立波刘波刘建北刘涛刘真娄辛丑马连良 Bruce Mellado 莫欣 Mila Pandurovic 钱剑明钱卓妮 Nikolaos Rompotis 阮曼奇 Alex Schuy 单连友史静远史欣苏淑芳王大勇王锦王连涛王贻芳魏彧骞许悦杨海军杨迎姚为民于丹张凯栗张照茹赵明锐赵祥虎周宁 Institute of High Energy Physics Department of Physics and Astronomy Iowa State University Department of Physics Southeast University Department of Engineering Physics Physics Department Tsinghua University School of Physics Peking University University of Chinese Academy of Science (UCAS) Physical Science Laboratory Huairou National Comprehensive Science Center School of Physics and Astronomy Shanghai Jiao Tong University KLPPAC-MoE SKLPPC Department of Physics University of Liverpool Kavli IPMU (WPI) UTIAS The University of Tokyo Department of Physics University of California PRISMA Cluster of Excellence & Mainz Institute of Theoretical Physics Johannes Gutenberg-Universit?t Mainz Department of Modern Physics University of Science and Technology of China Department of Physics & Astronomy University of Pittsburgh Tsung-Dao Lee Institute Department of Physics National Taiwan University Department of Physics University of Washington Department of Physics Nanjing University School of Nuclear Science and Technology University of South China Department of Physics University of Texas at Dallas Department of Physics and Center for High Energy and High Field Physics National Central University Institute of Frontier and Interdisciplinary Science and Key Laboratory of Particle Physics and Particle Irradiation (MOE) Shandong University Department of Physics Hong Kong University of Science and Technology Theoretical Physics Department Fermi National Accelerator Laboratory Maryland Center for Fundamental Physics Department of Physics University of Maryland School of Physics and Institute for Collider Particle Physics University of the Witwatersrand iThemba LABS National Research Foundation Vinca Institute of Nuclear Sciences University of Belgrade Department of Physics University of Michigan Center for Theoretical Physics of the Universe Institute of Basic Science Department of Physics University of Arizona Department of Physics University of Chicago Lawrence Berkeley National Laboratory Chi

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^+e^- circular collider proposed by and to be hosted in China.Located in a tunnel of approximately 100 km in circumference,it will operate at a center-of-mass energy of 240 GeV as the Higgs factory.In this paper,we present the first estimates on the precision of the Higgs boson property measurements achievable at the cepc and discuss implications of these measurements.

关键词： cepc Higgs bos on Higgs boson properties Higgs boson couplings Higgs factory effective field theory,EFT

Mixed electroweak-QCD corrections to e^+e^-→μ^+μ^-H at cepc with finite-width effect

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Chinese Physics C 2019年第1期43卷 75-83页

作者：陈文冯锋贾宇桑文龙 Institute of High Energy Physics Chinese Academy of Science School of Physics University of Chinese Academy of Sciences Department of Physics University of Alberta China University of Mining and Technology School of Physical Science and Technology Southwest University

The associated production of Higgs boson with a muon pair, e^+e^-→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 cepc.The projected accuracy of the corresponding cross section measurement is about per cent level at cepc. In this work, we investigate both O(α) weak correction and the O(ααs) 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.The mixed electroweak-QCD correction turns out to reach 1.5% of the Born-order result, and thereby must be included in future confrontation with the data. We also observe that, after including higher-order corrections, the simplified prediction for the integrated cross section employing the narrow-width-approximation may deviate from our full result by a few per cents.

关键词： cepc Higgs boson QCD corrections electroweak

环形正负电子对撞机注入引出分布参数型冲击磁铁设计

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强激光与粒子束 2023年第5期35卷 82-89页

作者：吴官健王磊王冠文史晓蕾翟心哲陈锦晖中国科学院大学核科学与技术学院北京100049 中国科学院高能物理研究所加速器中心北京100049

环形正负电子对撞机(cepc)是一台周长100 km,最高能量为120 GeV的双环对撞机。为了满足不同能量粒子从增强器注入到对撞环,针对W和Z能量模式设计了对撞环离轴注入系统,用于实现束流的累积。为了提高注入效率,兼容不同注入能量,不同束流... 详细信息

环形正负电子对撞机(cepc)是一台周长100 km,最高能量为120 GeV的双环对撞机。为了满足不同能量粒子从增强器注入到对撞环,针对W和Z能量模式设计了对撞环离轴注入系统,用于实现束流的累积。为了提高注入效率,兼容不同注入能量,不同束流填充模式,同时尽可能减少注入过程中冲击磁铁对其它束团的扰动,要求对撞环离轴注入冲击磁铁系统是一个上升时间和下降时间小于200 ns,脉冲底宽调节范围为440~2420 ns的梯形波脉冲放电系统。和常见的集中参数型冲击磁铁相比,分布参数型冲击磁铁具有更优越的动态响应特性,适合产生一个前沿更加陡峭、波形更为理想的梯形波脉冲。根据cepc的束流注入物理需求,完成了一台分布参数型冲击磁铁的物理设计和结构设计,并采用了PSpice和Opera程序进行模拟仿真。设计结果表明:冲击磁铁由26级LC单元结构叠装而成,磁铁总长为1018 mm,磁有效长度为942 mm;在[−20,20]mm磁铁孔径内,磁场强度为0.0421 T,磁场均匀性优于±0.2%;冲击磁铁系统总上升时间(10%~90%)为193 ns,下降时间(90%~10%)为191 ns。理论分析、PSpice程序和Opera程序模拟均验证了磁铁设计方案的可行性。

关键词： cepc 注入引出离轴注入快脉冲冲击磁铁分布参数型冲击磁铁

Sensitivity study of anomalous HZZ couplings at a future Higgs factory

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Chinese Physics C 2019年第10期43卷 1-6页

作者：李华东吕才典单连友 Institute of High Energy Physics CASBeijing 100049China School of Physics University of Chinese Academy of SciencesBeijing 100049China

We study the sensitivity of constraining the model independent HZZ coupling based on the effective theory up to dimension-6 operators at a future Higgs factory. Using the current conceptual design parameters of the Circular Electron Positron Collider, we give the experimental limits for the model independent operators given by the total Higgsstrahlung cross-section and the angular distribution of Z boson decays. In particular, we give the very small sensitivity limit for the CP violation parameter g, which will be a clear window to test the Standard Model and look for new physics signals.

关键词： Higgs new physics effective field theory cepc

Angular distribution coefficients of Z(W) boson produced in e^+e^- collisions at s^(1/2) = 240 GeV

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Chinese Physics C 2019年第4期43卷 54-62页

作者：王玉东王建雄 Institute of High Energy Physics Chinese Academy of Sciences School of Physics University of Chinese Academy of Sciences

At the designed circular electron-positron collider(cepc), similar to the hadron collider, the angular distribution coefficients of the decay lepton pair from the produced Z(W) boson in e^+e^- collisions are predicted. Their dependence on cosθZ(cosθW) are presented in four different polarization frames. Furthermore, the value of the angular distribution coefficients in different bins of cosθZ are presented in the C-S frame. In comparison with the case at the hadron collider, better accurate measurement for Z(W) is expected because there is less background, and W could be reconstructed from its leptonic decay channel. This works provides a method to precisely test the electroweak production mechanism or some effect induced from new physics in the future measurements at the cepc.

关键词： Drell-Yan process Z boson cepc angular distribution coefficients

Production and constraints for a massive dark photon at electron-positron colliders

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Chinese Physics C 2020年第2期44卷 62-71页

作者：蒋军李春园李世渊 Shankar Dayal Pathak 司宗国杨兴华 School of Physics Shandong UniversityJinanShandong 250100China Department of Physics Lovely Professional UniversityPhagwaraPunjab144411India

Dark sector may couple to the Standard Model via one or more mediator particles.We discuss two types of mediators:the dark photon A’and the dark scalar mediatorΦ.The total cross-sections and various differential distributions of the processes e+e-→qqA’and e+e→qqφ(q=u,d,c,s and b quarks)are discussed.We focus on the study of the invisible due to the cleaner background at future e+e-colliders.It is found that the kinematic distributions of the two-jet system could be used to identify(or exclude)the dark photon and the dark scalar mediator,as well as to distinguish between them.We further study the possibility of a search for dark photons at a future cepc experiment with s1/2=91.2 GeV and 240 GeV.With cepc running at s1/2=91.2 GeV,it would be possible to perform a decisive measurement of the dark photon(20 GeV

关键词： dark photon dark scalar mediator cepc

用于cepc探测器超导磁体的液氮虹吸实验研究

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低温与超导 2016年第9期44卷 13-17,38页

作者：李文双王美芬岳献芳尹少武王立朱自安张恺戴忠北京科技大学机械工程学院北京100083 中国科学院高能物理研究所北京100049

概括了环形正负电子对撞机(cepc)探测器超导磁体拟采用的虹吸冷却低温系统的研制背景,重点介绍了液氮虹吸实验平台的设计、组装及检漏。分别以氮气液化后的液氮填充相分离器的1/5和1/3体积的要求进行了两次实验,其常温常压下的体积分别... 详细信息

概括了环形正负电子对撞机(cepc)探测器超导磁体拟采用的虹吸冷却低温系统的研制背景,重点介绍了液氮虹吸实验平台的设计、组装及检漏。分别以氮气液化后的液氮填充相分离器的1/5和1/3体积的要求进行了两次实验,其常温常压下的体积分别为0.32m^3和0.47m^3。实验发现当充装量为0.32m^3时,蒸发侧加热功率达到10W后发生了烧干现象;充装量为0.47m^3时,蒸发侧加热功率达到20W后液氮回路仍循环良好,管路最大温差不到1K,管路温度分布均匀,未发生烧干现象。实验结果表明,氮气的充装量以及蒸发侧的加热功率是影响虹吸冷却效果的两个重要因素。

关键词： cepc 超导磁体液氮充装量热虹吸管