The circular electron-positron collider(CEPC)is designed to precisely measure the properties of the Higgs boson,study electroweak interactions at the Z-boson peak,and search for new physics beyond the Standard Model.A...The circular electron-positron collider(CEPC)is designed to precisely measure the properties of the Higgs boson,study electroweak interactions at the Z-boson peak,and search for new physics beyond the Standard Model.As a component of the 4th conceptual CEPC detector,the drift chamber facilitates the measurement of charged particles.This study implemented a Geant4-based simulation and track reconstruction for the drift chamber.For the simulation,detector construction and response were implemented and added to the CEPC simulation chain.The development of track reconstruction involves track finding using the combinatorial Kalman filter method and track fitting using the tool of GenFit.Using the simulated data,the tracking performance was studied.The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.展开更多
To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k...To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k W continuous wave(CW) klystron operating at frequency of 650-MHz has been designed. The results of beam–wave interaction simulation with several different codes are presented. The efficiency is optimized to be 65% with a second harmonic cavity in three-dimensional(3D) particle-in-cell code CST. The effect of cavity frequency error and mismatch load on efficiency of klystron have been investigated. The design and cold test of reentrant cavities are described, which meet the requirements of RF section design. So far, the manufacturing and high-power test of the first klystron prototype have been completed.When the gun operated at DC voltage of 80 k V and current of 15.4 A, the klystron peak power reached 804 k W with output efficiency of about 65.3% at 40% duty cycle. The 1-d B bandwidth is ±0.8 MHZ. Due to the crack of ceramic window, the CW power achieved about 700 kW. The high-power test results are in good agreement with 3D simulation.展开更多
Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures pre...Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.展开更多
Positron sources are one of the most important components of the injector of a circular electron positron collector(CEPC).The CEPC is designed as an e^(+)e^(−)collider for a Higgs factory.Its accelerator system is com...Positron sources are one of the most important components of the injector of a circular electron positron collector(CEPC).The CEPC is designed as an e^(+)e^(−)collider for a Higgs factory.Its accelerator system is composed of 100-km-long storage rings and an injector.The design goal of the positron source is to obtain positron beams with a bunch charge of 3 nC.The flux concentrator(FC)is one of the cores of the positron source.This paper reports the design,development,and measurements of an FC prototype system.The prototype includes an FC and an all-solid-state high-current pulse modulator.Preliminary tests show that the peak current on the FC can reach 15.5 kA,and the peak magnetic field can reach 6.2 T.The test results are consistent with the theoretical simulation.The FC system fulfills the requirements of the CEPC positron source as well as provides a reference for the development of similar devices both domestically and abroad.展开更多
随着环形正负电子对撞机(Circular Electron Positron Collider,CEPC)方案的提出,由硅光电倍增管(Silicon Photomultiplier,SiPM)和塑料闪烁体组成的读出单元作为电磁量能器的预研方案之一,逐渐成为研究热点。在探测器预研阶段需要对读...随着环形正负电子对撞机(Circular Electron Positron Collider,CEPC)方案的提出,由硅光电倍增管(Silicon Photomultiplier,SiPM)和塑料闪烁体组成的读出单元作为电磁量能器的预研方案之一,逐渐成为研究热点。在探测器预研阶段需要对读出单元性能进行充分研究,因此我们设计了一套自动化测试系统用于对读出单元进行测试、分析并改善其性能。利用DT5751波形采样插件、SiPM驱动电路板、步进电机、低压电源、继电器等完成硬件搭建,以LabVIEW为开发平台完成了软件的串行协议接口之间的通信,实现了读出单元的自动化测试,编写了相应的数据处理程序。在此基础上进行了SiPM刻度、闪烁体发光均匀性以及反射材料对光输出影响的研究。测试结果表明,ESR反射膜包裹的塑闪条具有最高的光输出,塑闪条耦合10μm像素SiPM的光输出为耦合25μm像素SiPM的三分之一。展开更多
束流垃圾桶的材料、结构、尺寸的正确设计对于确保高能环形对撞机(Circular Electron Positron Collider,CEPC)直线加速器的安全运行有重要意义。采用蒙特卡罗程序FLUKA,研究了概念设计阶段的CEPC直线加速器束流垃圾桶的初步设计方案,...束流垃圾桶的材料、结构、尺寸的正确设计对于确保高能环形对撞机(Circular Electron Positron Collider,CEPC)直线加速器的安全运行有重要意义。采用蒙特卡罗程序FLUKA,研究了概念设计阶段的CEPC直线加速器束流垃圾桶的初步设计方案,给出了作为吸收体设计依据的射程的不同计算方法及验证过程,以及屏蔽体部分的材料选择与总体屏蔽厚度的关系;计算过程中引入减方差技巧提高了计算结果的精确程度。展开更多
Purpose The circular electron-positron collider(CEPC)is a large international scientific facility with the goal of studying the Higgs particle.In order to achieve this goal,many sophisticated detectors need to be inst...Purpose The circular electron-positron collider(CEPC)is a large international scientific facility with the goal of studying the Higgs particle.In order to achieve this goal,many sophisticated detectors need to be installed.As the basis for the installation of the internal sub-detector,the iron yoke needs to have sufficient strength and accuracy to ensure the accuracy of the internal sub-detector installation.Two different designs of CEPC detector barrel iron yoke structure are proposed.Simulation and structural optimization of these two designs are carried out,and valuable reference is provided for the subsequent design and optimization.Methods The selection of an appropriate design for the CEPC detector barrel iron yoke necessitates adherence to mechanical design requirements.In this paper,two mechanical design schemes of barrel iron yoke structure are presented,including structural design and analysis,mechanical properties analysis,dynamic properties analysis and structural optimization.Results Under the condition of 600 mm thickness,the symmetrical structure and the spiral structure are designed.The finite element analysis is used to simulate the mechanical analysis,modal analysis and seismic analysis of the two structures.Compared with the simulation results,the mechanical properties and dynamic properties of the spiral structure are better than those of the symmetrical structure under this condition.Conclusion Utilizing finite element analysis,the mechanical properties and dynamic properties of the two structures were determined.Following comparative analysis,it has been determined that the mechanical properties and dynamic properties exhibited by the spiral structure may be more in line with mechanical design requirements for the thin iron yoke structure.This study serves as a valuable reference for future design and optimization endeavors concerning the CEPC detector barrel iron yoke structure.展开更多
The Circular Electron Positron Collider(CEPC)is a large-scale particle accelerator designed to collide electrons and positrons at high energies.One of its primary goals is to achieve high-precision measurements of the...The Circular Electron Positron Collider(CEPC)is a large-scale particle accelerator designed to collide electrons and positrons at high energies.One of its primary goals is to achieve high-precision measurements of the properties of the Higgs boson and is facilitated by the large number of Higgs bosons that are produced with significantly low contamination.The measurements of Higgs boson branching fractions into bb/cc/gg andττ/WW*/ZZ*,where the W or Z bosons decay hadronically,are presented in the context of the CEPC experiment,assuming a scenario with 5600 fb^(-1)of collision data at a center-of-mass energy of 240 GeV.In this study the Higgs bosons are produced in association with a Z boson,with the Z boson decaying into a pair of muons(μ^(+)μ^(-)),which have high efficiency and resolution.To separate all decay channels simultaneously with high accuracy,the Particle Flow Network(PFN),a graph-based machine learning model,is considered.The precise classification provided by the PFN is employed in measuring the branching fractions using the migration matrix method,which accurately corrects for detector effects in each decay channel.The statistical uncertainty of the measured branching ratio is estimated to be 0.55%in the H→bb final state and approximately 1.5%-16%in the H→cc/gg/ττ/WW*/ZZ*final states.In addition,the main sources of systematic uncertainties in the measurement of the branching fractions are discussed.展开更多
Purpose Future large high-luminosity electron–positron colliders such as circular electron positron collider(CEPC)and future circular collider(FCC-ee)require nanometer-sized beams at the interaction point(IP).The lum...Purpose Future large high-luminosity electron–positron colliders such as circular electron positron collider(CEPC)and future circular collider(FCC-ee)require nanometer-sized beams at the interaction point(IP).The luminosity is very sensitive to the beam orbit drifts at the IP.It is essential to have a fast luminosity feedback system at the IP to maintain optimum beam collision conditions and prevent a luminosity degradation due to orbit drifts in the presence of mechanical vibrations and dynamical imperfections.Methods We considered two possible methods for this purpose for CEPC:one based on measurements of the luminosity and the other based on measurements of the beam orbits around the IP.Results In this paper,we present the preliminary design consideration for a fast luminosity feedback system at the IP of CEPC.展开更多
1背景和动机2019年5月召开的格兰纳达(Granada)论坛是针对“The European Strategy for Particle Physics”(ESPP)所组织的研讨会,会上就国际高能物理界在希格斯粒子发现后如何推动高能物理基础研究达成了一些重要共识,特别是会议聚焦...1背景和动机2019年5月召开的格兰纳达(Granada)论坛是针对“The European Strategy for Particle Physics”(ESPP)所组织的研讨会,会上就国际高能物理界在希格斯粒子发现后如何推动高能物理基础研究达成了一些重要共识,特别是会议聚焦在将希格斯工厂作为未来对撞机的选项,并明确希格斯粒子性质的研究将是揭示隐藏在目前粒子物理标准模型后面更深层次基本规律的关键.展开更多
The decay of Higgs boson into two spin-1/2 particles provides an ideal system to reveal quantum entanglement and Bell-nonlocality.Future e^(+)e^(-) colliders can improve the measurement accuracy of the spin correlatio...The decay of Higgs boson into two spin-1/2 particles provides an ideal system to reveal quantum entanglement and Bell-nonlocality.Future e^(+)e^(-) colliders can improve the measurement accuracy of the spin correlation of tau lepton pairs from Higgs boson decay.We show the testability of Bell inequality through h→ττ at Circular Electron Positron Collider(CEPC).Two realistic methods of testing Bell inequality are investigated,i.e.,Törnqvist's method and Clauser-Home-Shimony-Holt(CHSH)inequality.In the simulation,we consider the detector effects of CEPC including uncertainties for tracks and jets from Z boson in the production of e^(+)e^(-)→Zh.Necessary reconstruction approaches are described to measure quantum entanglement between τ^(+) and τ^(-).Finally,we show the sensitivity of CEPC to Bell inequality violation for the two methods.展开更多
As a Higgs factory, the CEPC(Circular Electron-Positron Collider) project aims at precision measurements of the Higgs boson properties. A baseline detector concept, APODIS(A PFA Oriented Detector for the HIggS factory...As a Higgs factory, the CEPC(Circular Electron-Positron Collider) project aims at precision measurements 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 for this baseline design with ■ Higgs events. The detector performance for reconstructing charged particles, photons and jets is quantified with H→μμ, γγ and jet final states, respectively. The resolutions of reconstructed Higgs boson mass are comparable for the different decay modes with jets in the final states. We also analyze the H→WW~* and ZZ* decay modes, where a clear separation between different decay cascades is observed.展开更多
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 Ge V. The CEPC will accumulate an...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 Ge V. The CEPC will accumulate an integrated luminosity of 5 ab-1over ten years of 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 a dedicated fast simulation tool, we have evaluated the statistical precisions of the Higgstrahlung cross section σZH and the Higgs mass m H measurement at the CEPC in the Z →μ~＋μ^-channel. The statistical precision of σZH（m_H） measurement could reach 0.97%（6.9 MeV） in the model-independent analysis which uses only the information from Z boson decays. For the standard model Higgs boson, the m H precision could be improved to 5.4 Me V by including the information from Higgs decays. The impact of the TPC size on these measurements is investigated. In addition, we studied the prospect of measuring the Higgs boson decaying into invisible final states at the CEPC. With the Standard Model ZH production rate, the upper limit of B（H → inv.） could reach 1.2% at 95% confidence level.展开更多
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 th...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.展开更多
Purpose CMOS pixel sensor has become extremely attractive for future high-performance tracking devices.It has been proposed for the vertex detector at the Circular Electron Positron Collider,which will allow precision...Purpose CMOS pixel sensor has become extremely attractive for future high-performance tracking devices.It has been proposed for the vertex detector at the Circular Electron Positron Collider,which will allow precision measurements of the properties of the Higgs boson.To meet the stringent requirements for low power consumption,it is necessary to optimize the pixel sensor diode geometry to reach a high charge-over-capacitance ratio that allows reduction in analog power consumption.Methods Collection electrode size and footprint are two critical elements in sensor diode geometry and have deciding impacts on the charge collection performance.A prototype CMOS pixel sensor,named JadePix-1,has been developed with pixel sectors implemented with different electrode sizes and footprints,and its charge collection performance has been characterized with radioactive sources.Results Charge-to-voltage conversion gains for pixel sectors under test have been calibrated with low-energy X-rays.Characterization results have been obtained for equivalent noise charge(below 10e−),charge collection efficiency(around 40%),charge-over-capacitance ratio(above 0.015 V)and signal-to-noise ratio(higher than 55).Conclusion Small collection electrode size and large footprint are preferred to achieve high charge-over-capacitance ratio that promises low analog power consumption.Ongoing studies on sensor performance before and after irradiation,combined with this work,will conclude the diode geometry optimization.展开更多
Background CEPC is a 100-kilometer-long electron-position collider,aiming to produce Higgs,W and Z-pole.Double ring(DR)is the baseline design of its main ring,and advanced partial double ring(APDR)is the alternative o...Background CEPC is a 100-kilometer-long electron-position collider,aiming to produce Higgs,W and Z-pole.Double ring(DR)is the baseline design of its main ring,and advanced partial double ring(APDR)is the alternative one.Purpose The purpose of this paper is to study the beam loading effects and the corresponding longitudinal beam dynamics of CEPC DR and APDR.Methods The phase shift of the bunches modulated by the bunch gap is calculated with the approximation formulas and simulated with the program.All these methods are compared,and the application conditions of them are also elaborated.In addition,the longitudinal coupled-bunch instability in CEPC main ring is calculated by analytical formulas.Results In CEPC DR high-lumi Z,the phase shift can be reduced to 0.51 deg(°).Besides,the total number of unstable longitudinal modes is 15 in CEPC DR high-lumi Z when no feedback system is added.Conclusion The phase shift of the bunches in CEPC can be reduced to an acceptable value if the optimal filling pattern is chosen.For CEPC APDR,the RF parameters are calculated and the beam loading effects are tolerable.展开更多
Background Circular electron positron collider(CEPC)is a 100-km electron positron collider proposed by IHEP.The longitudinal coupled-bunch instability(LCBI)of CEPC main ring operating to study the Z particle(Z machine...Background Circular electron positron collider(CEPC)is a 100-km electron positron collider proposed by IHEP.The longitudinal coupled-bunch instability(LCBI)of CEPC main ring operating to study the Z particle(Z machine)may be a limiting factor of CEPC and needs to be considered seriously.Purpose The purposes of this paper are to calculate the LCBI caused by the fundamental mode of superconducting RF cavities in CEPC main ring,which is the most critical impedance,and to complete the design of the RF feedback systems suitable for CEPC,whose specifications can suppress the LCBI to a manageable level.Methods The LCBI growth rate in the CEPC main ring is calculated in the frequency domain.Two kinds of RF feedback,i.e.,direct feedback and one-turn delay feedback,are simulated with the program to suppress the LCBI.And according to the suppression effect of LCBI growth rate after adding RF feedback,the required design parameters are given.Results Two operation conditions of Z machine have severe LCBI without suppression,and dozens of longitudinal modes are unstable.Only the direct RF feedback is needed to suppress LCBI in the case of Z-30 MW,while both the direct RF feedback with maximum gain and one-turn feedback are needed in the case of Z-50 MW.The LCBI growth rates can be reduced to the order of half frequency of the synchronous oscillation.Conclusion The LCBI of CEPC Z machine has been studied.Selecting appropriate feedback RF feedback can reduce the LCBI to an acceptable value that bunch by bunch feedback can suppress.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.12025502 and 12341504)。
文摘The circular electron-positron collider(CEPC)is designed to precisely measure the properties of the Higgs boson,study electroweak interactions at the Z-boson peak,and search for new physics beyond the Standard Model.As a component of the 4th conceptual CEPC detector,the drift chamber facilitates the measurement of charged particles.This study implemented a Geant4-based simulation and track reconstruction for the drift chamber.For the simulation,detector construction and response were implemented and added to the CEPC simulation chain.The development of track reconstruction involves track finding using the combinatorial Kalman filter method and track fitting using the tool of GenFit.Using the simulated data,the tracking performance was studied.The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.
基金Project supported by Yifang Wang’s Science Studio of the Ten Thousand Talents Project。
文摘To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k W continuous wave(CW) klystron operating at frequency of 650-MHz has been designed. The results of beam–wave interaction simulation with several different codes are presented. The efficiency is optimized to be 65% with a second harmonic cavity in three-dimensional(3D) particle-in-cell code CST. The effect of cavity frequency error and mismatch load on efficiency of klystron have been investigated. The design and cold test of reentrant cavities are described, which meet the requirements of RF section design. So far, the manufacturing and high-power test of the first klystron prototype have been completed.When the gun operated at DC voltage of 80 k V and current of 15.4 A, the klystron peak power reached 804 k W with output efficiency of about 65.3% at 40% duty cycle. The 1-d B bandwidth is ±0.8 MHZ. Due to the crack of ceramic window, the CW power achieved about 700 kW. The high-power test results are in good agreement with 3D simulation.
文摘Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.
基金This work was supported by the National Key Programme for S&T Research and Development(No.2016YFA0400400)the Youth Innovation Promotion Association CAS(2019016).
文摘Positron sources are one of the most important components of the injector of a circular electron positron collector(CEPC).The CEPC is designed as an e^(+)e^(−)collider for a Higgs factory.Its accelerator system is composed of 100-km-long storage rings and an injector.The design goal of the positron source is to obtain positron beams with a bunch charge of 3 nC.The flux concentrator(FC)is one of the cores of the positron source.This paper reports the design,development,and measurements of an FC prototype system.The prototype includes an FC and an all-solid-state high-current pulse modulator.Preliminary tests show that the peak current on the FC can reach 15.5 kA,and the peak magnetic field can reach 6.2 T.The test results are consistent with the theoretical simulation.The FC system fulfills the requirements of the CEPC positron source as well as provides a reference for the development of similar devices both domestically and abroad.
文摘随着环形正负电子对撞机(Circular Electron Positron Collider,CEPC)方案的提出,由硅光电倍增管(Silicon Photomultiplier,SiPM)和塑料闪烁体组成的读出单元作为电磁量能器的预研方案之一,逐渐成为研究热点。在探测器预研阶段需要对读出单元性能进行充分研究,因此我们设计了一套自动化测试系统用于对读出单元进行测试、分析并改善其性能。利用DT5751波形采样插件、SiPM驱动电路板、步进电机、低压电源、继电器等完成硬件搭建,以LabVIEW为开发平台完成了软件的串行协议接口之间的通信,实现了读出单元的自动化测试,编写了相应的数据处理程序。在此基础上进行了SiPM刻度、闪烁体发光均匀性以及反射材料对光输出影响的研究。测试结果表明,ESR反射膜包裹的塑闪条具有最高的光输出,塑闪条耦合10μm像素SiPM的光输出为耦合25μm像素SiPM的三分之一。
文摘束流垃圾桶的材料、结构、尺寸的正确设计对于确保高能环形对撞机(Circular Electron Positron Collider,CEPC)直线加速器的安全运行有重要意义。采用蒙特卡罗程序FLUKA,研究了概念设计阶段的CEPC直线加速器束流垃圾桶的初步设计方案,给出了作为吸收体设计依据的射程的不同计算方法及验证过程,以及屏蔽体部分的材料选择与总体屏蔽厚度的关系;计算过程中引入减方差技巧提高了计算结果的精确程度。
基金supported by Experimental Physics Center,Institute of High Energy Physics,Chinese Academy of Sciences[Y9291309U2].
文摘Purpose The circular electron-positron collider(CEPC)is a large international scientific facility with the goal of studying the Higgs particle.In order to achieve this goal,many sophisticated detectors need to be installed.As the basis for the installation of the internal sub-detector,the iron yoke needs to have sufficient strength and accuracy to ensure the accuracy of the internal sub-detector installation.Two different designs of CEPC detector barrel iron yoke structure are proposed.Simulation and structural optimization of these two designs are carried out,and valuable reference is provided for the subsequent design and optimization.Methods The selection of an appropriate design for the CEPC detector barrel iron yoke necessitates adherence to mechanical design requirements.In this paper,two mechanical design schemes of barrel iron yoke structure are presented,including structural design and analysis,mechanical properties analysis,dynamic properties analysis and structural optimization.Results Under the condition of 600 mm thickness,the symmetrical structure and the spiral structure are designed.The finite element analysis is used to simulate the mechanical analysis,modal analysis and seismic analysis of the two structures.Compared with the simulation results,the mechanical properties and dynamic properties of the spiral structure are better than those of the symmetrical structure under this condition.Conclusion Utilizing finite element analysis,the mechanical properties and dynamic properties of the two structures were determined.Following comparative analysis,it has been determined that the mechanical properties and dynamic properties exhibited by the spiral structure may be more in line with mechanical design requirements for the thin iron yoke structure.This study serves as a valuable reference for future design and optimization endeavors concerning the CEPC detector barrel iron yoke structure.
基金Supported in part by the National Key R&D Program of China(2022YFE0116900)the Basic Science Center Program(12188102)by National Natural Science Foundation of China。
文摘The Circular Electron Positron Collider(CEPC)is a large-scale particle accelerator designed to collide electrons and positrons at high energies.One of its primary goals is to achieve high-precision measurements of the properties of the Higgs boson and is facilitated by the large number of Higgs bosons that are produced with significantly low contamination.The measurements of Higgs boson branching fractions into bb/cc/gg andττ/WW*/ZZ*,where the W or Z bosons decay hadronically,are presented in the context of the CEPC experiment,assuming a scenario with 5600 fb^(-1)of collision data at a center-of-mass energy of 240 GeV.In this study the Higgs bosons are produced in association with a Z boson,with the Z boson decaying into a pair of muons(μ^(+)μ^(-)),which have high efficiency and resolution.To separate all decay channels simultaneously with high accuracy,the Particle Flow Network(PFN),a graph-based machine learning model,is considered.The precise classification provided by the PFN is employed in measuring the branching fractions using the migration matrix method,which accurately corrects for detector effects in each decay channel.The statistical uncertainty of the measured branching ratio is estimated to be 0.55%in the H→bb final state and approximately 1.5%-16%in the H→cc/gg/ττ/WW*/ZZ*final states.In addition,the main sources of systematic uncertainties in the measurement of the branching fractions are discussed.
基金Supported by the National Natural Science Foundation of China(Grant No.12175249).
文摘Purpose Future large high-luminosity electron–positron colliders such as circular electron positron collider(CEPC)and future circular collider(FCC-ee)require nanometer-sized beams at the interaction point(IP).The luminosity is very sensitive to the beam orbit drifts at the IP.It is essential to have a fast luminosity feedback system at the IP to maintain optimum beam collision conditions and prevent a luminosity degradation due to orbit drifts in the presence of mechanical vibrations and dynamical imperfections.Methods We considered two possible methods for this purpose for CEPC:one based on measurements of the luminosity and the other based on measurements of the beam orbits around the IP.Results In this paper,we present the preliminary design consideration for a fast luminosity feedback system at the IP of CEPC.
文摘1背景和动机2019年5月召开的格兰纳达(Granada)论坛是针对“The European Strategy for Particle Physics”(ESPP)所组织的研讨会,会上就国际高能物理界在希格斯粒子发现后如何推动高能物理基础研究达成了一些重要共识,特别是会议聚焦在将希格斯工厂作为未来对撞机的选项,并明确希格斯粒子性质的研究将是揭示隐藏在目前粒子物理标准模型后面更深层次基本规律的关键.
基金Supported by the National Natural Science Foundation of China(12375096,12035008,11975129)"the Fundamental Research Funds for the Central Universities",Nankai University(63196013)+1 种基金Kai Ma was supported by the Natural Science Basic Research Program of Shaanxi Province,China(2023-JC-YB-041)the Innovation Capability Support Program of Shaanxi Province,China(2021KJXX-47)。
文摘The decay of Higgs boson into two spin-1/2 particles provides an ideal system to reveal quantum entanglement and Bell-nonlocality.Future e^(+)e^(-) colliders can improve the measurement accuracy of the spin correlation of tau lepton pairs from Higgs boson decay.We show the testability of Bell inequality through h→ττ at Circular Electron Positron Collider(CEPC).Two realistic methods of testing Bell inequality are investigated,i.e.,Törnqvist's method and Clauser-Home-Shimony-Holt(CHSH)inequality.In the simulation,we consider the detector effects of CEPC including uncertainties for tracks and jets from Z boson in the production of e^(+)e^(-)→Zh.Necessary reconstruction approaches are described to measure quantum entanglement between τ^(+) and τ^(-).Finally,we show the sensitivity of CEPC to Bell inequality violation for the two methods.
基金Supported by National Key Program for S&T Research and Development(2016YFA0400400)the National Natural Science Foundation of China(11675202)the Hundred Talent programs of Chinese Academy of Science(Y3515540U1)
文摘As a Higgs factory, the CEPC(Circular Electron-Positron Collider) project aims at precision measurements 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 for this baseline design with ■ Higgs events. The detector performance for reconstructing charged particles, photons and jets is quantified with H→μμ, γγ and jet final states, respectively. The resolutions of reconstructed Higgs boson mass are comparable for the different decay modes with jets in the final states. We also analyze the H→WW~* and ZZ* decay modes, where a clear separation between different decay cascades is observed.
基金Supported by the Joint Funds of the NSFC(U1232105)CAS Hundred Talent Program(Y3515540U1)
文摘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 Ge V. The CEPC will accumulate an integrated luminosity of 5 ab-1over ten years of 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 a dedicated fast simulation tool, we have evaluated the statistical precisions of the Higgstrahlung cross section σZH and the Higgs mass m H measurement at the CEPC in the Z →μ~＋μ^-channel. The statistical precision of σZH（m_H） measurement could reach 0.97%（6.9 MeV） in the model-independent analysis which uses only the information from Z boson decays. For the standard model Higgs boson, the m H precision could be improved to 5.4 Me V by including the information from Higgs decays. The impact of the TPC size on these measurements is investigated. In addition, we studied the prospect of measuring the Higgs boson decaying into invisible final states at the CEPC. With the Standard Model ZH production rate, the upper limit of B（H → inv.） could reach 1.2% at 95% confidence level.
基金Supported by the National Key Program for S&T Researh and Development(2016YFA0400400)CAS Center for Excellence in Particle Physics+12 种基金Yifang Wang’s Science Studio of the Ten Thousand Talents Projectthe CAS/SAFEA International Partnership Program for Creative Research Teams(H751S018S5)IHEP Innovation Grant(Y4545170Y2)Key Research Program of Frontier Sciences,CAS(XQYZDY-SSW-SLH002)Chinese Academy of Science Special Grant for Large Scientific Project(113111KYSB20170005)the National Natural Science Foundation of China(11675202)the Hundred Talent Programs of Chinese Academy of Science(Y3515540U1)the National 1000 Talents Program of ChinaFermi Research Alliance,LLC(DE-AC02-07CH11359)the NSF(PHY1620074)by the Maryland Center for Fundamental Physics(MCFP)Tsinghua University Initiative Scientific Research Programthe Beijing Municipal Science and Technology Commission project(Z181100004218003)
文摘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.
基金the National Natural Science Foundation of China(Nos.11505207,11573028)the State Key Laboratory of Particle Detection and Electronics,the CAS Center for Excellence in Particle Physics(CCEPP)and the IHEP Innovation Fund and the International Partnership Program of Chinese Academy of Sciences.
文摘Purpose CMOS pixel sensor has become extremely attractive for future high-performance tracking devices.It has been proposed for the vertex detector at the Circular Electron Positron Collider,which will allow precision measurements of the properties of the Higgs boson.To meet the stringent requirements for low power consumption,it is necessary to optimize the pixel sensor diode geometry to reach a high charge-over-capacitance ratio that allows reduction in analog power consumption.Methods Collection electrode size and footprint are two critical elements in sensor diode geometry and have deciding impacts on the charge collection performance.A prototype CMOS pixel sensor,named JadePix-1,has been developed with pixel sectors implemented with different electrode sizes and footprints,and its charge collection performance has been characterized with radioactive sources.Results Charge-to-voltage conversion gains for pixel sectors under test have been calibrated with low-energy X-rays.Characterization results have been obtained for equivalent noise charge(below 10e−),charge collection efficiency(around 40%),charge-over-capacitance ratio(above 0.015 V)and signal-to-noise ratio(higher than 55).Conclusion Small collection electrode size and large footprint are preferred to achieve high charge-over-capacitance ratio that promises low analog power consumption.Ongoing studies on sensor performance before and after irradiation,combined with this work,will conclude the diode geometry optimization.
基金This study was supported by National Key Programme for S&T Research and Development(Grant No.:2016YFA0400400)National Natural Science Foundation of China(No.11575218)Key research Program of Frontier Science,CAS(Grant No.:QYZDJ-SSW-SLH004).
文摘Background CEPC is a 100-kilometer-long electron-position collider,aiming to produce Higgs,W and Z-pole.Double ring(DR)is the baseline design of its main ring,and advanced partial double ring(APDR)is the alternative one.Purpose The purpose of this paper is to study the beam loading effects and the corresponding longitudinal beam dynamics of CEPC DR and APDR.Methods The phase shift of the bunches modulated by the bunch gap is calculated with the approximation formulas and simulated with the program.All these methods are compared,and the application conditions of them are also elaborated.In addition,the longitudinal coupled-bunch instability in CEPC main ring is calculated by analytical formulas.Results In CEPC DR high-lumi Z,the phase shift can be reduced to 0.51 deg(°).Besides,the total number of unstable longitudinal modes is 15 in CEPC DR high-lumi Z when no feedback system is added.Conclusion The phase shift of the bunches in CEPC can be reduced to an acceptable value if the optimal filling pattern is chosen.For CEPC APDR,the RF parameters are calculated and the beam loading effects are tolerable.
文摘Background Circular electron positron collider(CEPC)is a 100-km electron positron collider proposed by IHEP.The longitudinal coupled-bunch instability(LCBI)of CEPC main ring operating to study the Z particle(Z machine)may be a limiting factor of CEPC and needs to be considered seriously.Purpose The purposes of this paper are to calculate the LCBI caused by the fundamental mode of superconducting RF cavities in CEPC main ring,which is the most critical impedance,and to complete the design of the RF feedback systems suitable for CEPC,whose specifications can suppress the LCBI to a manageable level.Methods The LCBI growth rate in the CEPC main ring is calculated in the frequency domain.Two kinds of RF feedback,i.e.,direct feedback and one-turn delay feedback,are simulated with the program to suppress the LCBI.And according to the suppression effect of LCBI growth rate after adding RF feedback,the required design parameters are given.Results Two operation conditions of Z machine have severe LCBI without suppression,and dozens of longitudinal modes are unstable.Only the direct RF feedback is needed to suppress LCBI in the case of Z-30 MW,while both the direct RF feedback with maximum gain and one-turn feedback are needed in the case of Z-50 MW.The LCBI growth rates can be reduced to the order of half frequency of the synchronous oscillation.Conclusion The LCBI of CEPC Z machine has been studied.Selecting appropriate feedback RF feedback can reduce the LCBI to an acceptable value that bunch by bunch feedback can suppress.
