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
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
In this study,we systematically investigate collider constraints on effective interactions between Dark Matter(DM)particles and electroweak gauge bosons.We consider the simplified models in which scalar or Dirac fermi...In this study,we systematically investigate collider constraints on effective interactions between Dark Matter(DM)particles and electroweak gauge bosons.We consider the simplified models in which scalar or Dirac fermion DM candidates couple only to electro weak gauge bosons through high dimensional effective operators.Considering the induced DM-quarks and DM-gluons operators from the Renormalization Group Evolution(RGE)running effect,we present comprehensive constraints on the effective energy scaleΛand Wilson coefficients CB(Λ),CW(Λ)from direct detection,indirect detection,and collider searches.In particular,we present the corresponding sensitivity from the Large Hadron Electron Collider(LHeC)and Future Circular Collider in the electronproton mode(FCC-ep)for the first time,update the mono-j and mono-γsearch limits at the Large Hadron Collider(LHC),and derive the new limits at the Circular Electron Positron Collider(CEPC).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
At the CEPC （Circular Electron Positron Collider）, which is proposed by the Chinese high energy physics community, the dominant background comes from radiative Bhabha scattering and the beamstrahlung effect accordin...At the CEPC （Circular Electron Positron Collider）, which is proposed by the Chinese high energy physics community, the dominant background comes from radiative Bhabha scattering and the beamstrahlung effect according to preliminary research. Therefore, it is necessary to incorporate a collimator system to intercept particles that may be lost near the interaction region （IR）. In this paper, we introduce some limitations in choosing the position and width of the collimators. A certain parameter range is determined which is confined by the β function and the width of the collimators. A suitable choice of the half width is made by exploring this parameter range. A simulation of the particle loss rate in the IR and the hit density in the vertex detector with and without the collimators shows that the set of parameters of the collimators we designed is appropriate and effective.展开更多
Purpose A high-performance tracking system will be crucial for the realization of the full physics potential of the Circular Electron Positron Collider(CEPC)project.Abaseline tracker has been proposed in the Conceptua...Purpose A high-performance tracking system will be crucial for the realization of the full physics potential of the Circular Electron Positron Collider(CEPC)project.Abaseline tracker has been proposed in the Conceptual Design Report and requires detailed studies of the layout geometry and comprehensive understanding of its tracking performance.Methods A Common Tracking Software(ACTS)is an experiment-independent software package and introduced for the track reconstruction for particle and nuclear physics experiments.The CEPC baseline tracker geometry has been implemented in ACTS,and its tracking performance has been evaluated with the provided track finding and fitting algorithms based on the truth tracking method.Results and Conclusion The tracking geometry implemented in ACTS,including the sensitive elements and simplified material distribution,has been validated.The track parameter resolutions obtained with ACTS are consistent with the full simulation results over the momentum range under investigation.ACTS has proven to be an excellent platform for the tracking performance evaluation and the tracker layout optimization.展开更多
This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collide...This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collider(CEPC).Simulated Monte Carlo events were generated and scaled to an integrated luminosity of 5.6 ab^(-1) to mimic the data.Extrapolated results to 20 ab^(-1) are also reported.The expected statistical precision of these measurements after combining three channels of Z boson decay was 7.7%.With some preliminary estimation on the systematical uncertainties,the total precision is 7.9%.The performance of the CEPC electro-magnetic calorimeter(ECAL) was studied by smearing the photon energy resolution in simulated events in the e^(+)e^(-)→ZH→qqγγ channel.In the present ECAL design,the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in the H→γγ channel.The impact of the resolution on the measured precision of σ(ZH)×Br(ZH→qqγγ) as well as the optimization of the ECAL constant and stochastic terms were studied for further detector design.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
Background The circular electron–positron collider(CEPC)is a double-ring collider proposed by Chinese scientists.It will be operated at centre-of-mass energy of 240,90,160 GeV and maybe also 360 GeV.Purpose The total...Background The circular electron–positron collider(CEPC)is a double-ring collider proposed by Chinese scientists.It will be operated at centre-of-mass energy of 240,90,160 GeV and maybe also 360 GeV.Purpose The total energy stored in the collider is up to 20 MJ.It is important to extract beams safely and not to damage the dump.In this paper,a dumping system including dilution kickers and absorber core with iron shielding is discussed.Methods The Monte Carlo code FLUKA is used to obtain the deposited energy and dose-equivalent distributions.The temperature rises are calculated assuming no heat conduction.Results Compared with the melting point and upper limit of dose equivalent,the magnets parameters are determined and the dimensions of the core and shielding are optimized.Conclusion The design of the dumping system meets the requirement that the energy stored in the collider can be absorbed safely.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 Circular Electron-Positron CoUider （CEPC） is one of the largest projects planned for high energy physics in China. It would serve first as a Higgs factory and then upgrade to a hadron collider. In this paper we ...The Circular Electron-Positron CoUider （CEPC） is one of the largest projects planned for high energy physics in China. It would serve first as a Higgs factory and then upgrade to a hadron collider. In this paper we give the 50 km and 100 km design for both single ring and double ring schemes, including Z boson, W boson and Higgs boson, by using an optimized method. Also, we give the potential of CEPC running at the Z and W poles. We analyse the relationship of luminosity with circumference and filling factor, which gives a way to evaluate the choice of geometry, and compare the nominal performances of CEPC-SPPC, LHC and FCC.展开更多
In this paper we will show a cavity and higher order mode （HOM） coupler designing scheme for the Circular Electron-positron Collider （CEPC） main ring. The cavity radio frequency （RF） design parameters are shown ...In this paper we will show a cavity and higher order mode （HOM） coupler designing scheme for the Circular Electron-positron Collider （CEPC） main ring. The cavity radio frequency （RF） design parameters are shown in this paper. The HOM power is calculated based on the beam parameters in the Preliminary Conceptual Design Report （Pre-CDR）. The damping results of the higher order modes （HOMs） and same order modes （SOMs） show that they reach the damping requirements for beam stability.展开更多
It is difficult to measure the WW-fusion Higgs production process （e＋e-→vvh） at a lepton collider with a center of mass energy of 240-250 GeV due to its small rate and tile large background from the Higgsstrahlung...It is difficult to measure the WW-fusion Higgs production process （e＋e-→vvh） at a lepton collider with a center of mass energy of 240-250 GeV due to its small rate and tile large background from the Higgsstrahlung proeess with an invisible Z （e＋e- → hZ,Z-4→vv）. We construct a modified recoil mass variable, mprecoil, defined using only the 3-momentum of the reconstructed Higgs particle, and show that it can separate the WW-fusion and Higgsstrahhlng events bettcr than the original recoil mass variable m recoil. Consequently, the variable can be used to improve the overall precisions of the extracted Higgs couplings, in both the conventional framework and the effective-field-theory framework. We also explorc the application of the mprecoil variable in the inclusive cross section mcasurements of the Higgsstrahlung process, while a quantitive analysis is left for future studies.展开更多
In this work, we study the response of a single layer Thick Gaseous Electron Multiplier （THGEM） detector to p/π＋ at the E3 line of the Beijing Test Beam Facility. The THGEM detector drift gap used in this study is...In this work, we study the response of a single layer Thick Gaseous Electron Multiplier （THGEM） detector to p/π＋ at the E3 line of the Beijing Test Beam Facility. The THGEM detector drift gap used in this study is 4 mm, and the gain of the detector operated in Ar＋3% iC4H10 is about 2000. p/π＋ particles at momenta between 500 MeV/c and 1000 MeV/c are distinguished by a Time Of Flight system. Our results show that at the measured momenta, detection efficiencies for p are from 93% to 99%, and for π＋ in the range of 82%-88%. Meanwhile, simple Geant4 simulations also have been done, and are consistent with the amplitude spectra of the beam test results. We preliminarily study the feasibility of the THGEM detector as a sampling element for a Digital Hadronic Calorimeter （DHCAL）, which may provide support for the possible application of a THGEM detector in the Circular Electron Positron Collider （CEPC） HCAL.展开更多
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...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.展开更多
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RD is Supported in part by the National Key R&D Programme of China(2021YFC2203100)YZ is Supported in part by the National Natural Science Foundation of China(11805001)the Fundamental Research Funds for the Central Universities(JZ2023HGTB0222)。
文摘In this study,we systematically investigate collider constraints on effective interactions between Dark Matter(DM)particles and electroweak gauge bosons.We consider the simplified models in which scalar or Dirac fermion DM candidates couple only to electro weak gauge bosons through high dimensional effective operators.Considering the induced DM-quarks and DM-gluons operators from the Renormalization Group Evolution(RGE)running effect,we present comprehensive constraints on the effective energy scaleΛand Wilson coefficients CB(Λ),CW(Λ)from direct detection,indirect detection,and collider searches.In particular,we present the corresponding sensitivity from the Large Hadron Electron Collider(LHeC)and Future Circular Collider in the electronproton mode(FCC-ep)for the first time,update the mono-j and mono-γsearch limits at the Large Hadron Collider(LHC),and derive the new limits at the Circular Electron Positron Collider(CEPC).
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.
文摘At the CEPC （Circular Electron Positron Collider）, which is proposed by the Chinese high energy physics community, the dominant background comes from radiative Bhabha scattering and the beamstrahlung effect according to preliminary research. Therefore, it is necessary to incorporate a collimator system to intercept particles that may be lost near the interaction region （IR）. In this paper, we introduce some limitations in choosing the position and width of the collimators. A certain parameter range is determined which is confined by the β function and the width of the collimators. A suitable choice of the half width is made by exploring this parameter range. A simulation of the particle loss rate in the IR and the hit density in the vertex detector with and without the collimators shows that the set of parameters of the collimators we designed is appropriate and effective.
基金The work is supported by the National Natural Science Foundation of China(GrantNo.11905237).
文摘Purpose A high-performance tracking system will be crucial for the realization of the full physics potential of the Circular Electron Positron Collider(CEPC)project.Abaseline tracker has been proposed in the Conceptual Design Report and requires detailed studies of the layout geometry and comprehensive understanding of its tracking performance.Methods A Common Tracking Software(ACTS)is an experiment-independent software package and introduced for the track reconstruction for particle and nuclear physics experiments.The CEPC baseline tracker geometry has been implemented in ACTS,and its tracking performance has been evaluated with the provided track finding and fitting algorithms based on the truth tracking method.Results and Conclusion The tracking geometry implemented in ACTS,including the sensitive elements and simplified material distribution,has been validated.The track parameter resolutions obtained with ACTS are consistent with the full simulation results over the momentum range under investigation.ACTS has proven to be an excellent platform for the tracking performance evaluation and the tracker layout optimization.
基金Supported by the IHEP Innovative Project on Sciences and Technologies (E2545AU210)。
文摘This paper presents the prospects of measuring σ(e^(+)e^(-)→ZH)× Br(H→γγ) in three Z decay channels Z→qq/μ^(+)μ^(-)/vv using the baseline detector with √s=240GeV at the Circular Electron Positron Collider(CEPC).Simulated Monte Carlo events were generated and scaled to an integrated luminosity of 5.6 ab^(-1) to mimic the data.Extrapolated results to 20 ab^(-1) are also reported.The expected statistical precision of these measurements after combining three channels of Z boson decay was 7.7%.With some preliminary estimation on the systematical uncertainties,the total precision is 7.9%.The performance of the CEPC electro-magnetic calorimeter(ECAL) was studied by smearing the photon energy resolution in simulated events in the e^(+)e^(-)→ZH→qqγγ channel.In the present ECAL design,the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in the H→γγ channel.The impact of the resolution on the measured precision of σ(ZH)×Br(ZH→qqγγ) as well as the optimization of the ECAL constant and stochastic terms were studied for further detector design.
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.
文摘Background The circular electron–positron collider(CEPC)is a double-ring collider proposed by Chinese scientists.It will be operated at centre-of-mass energy of 240,90,160 GeV and maybe also 360 GeV.Purpose The total energy stored in the collider is up to 20 MJ.It is important to extract beams safely and not to damage the dump.In this paper,a dumping system including dilution kickers and absorber core with iron shielding is discussed.Methods The Monte Carlo code FLUKA is used to obtain the deposited energy and dose-equivalent distributions.The temperature rises are calculated assuming no heat conduction.Results Compared with the melting point and upper limit of dose equivalent,the magnets parameters are determined and the dimensions of the core and shielding are optimized.Conclusion The design of the dumping system meets the requirement that the energy stored in the collider can be absorbed safely.
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 Natural Science Foundation of China(11175192,11505198)
文摘The Circular Electron-Positron CoUider （CEPC） is one of the largest projects planned for high energy physics in China. It would serve first as a Higgs factory and then upgrade to a hadron collider. In this paper we give the 50 km and 100 km design for both single ring and double ring schemes, including Z boson, W boson and Higgs boson, by using an optimized method. Also, we give the potential of CEPC running at the Z and W poles. We analyse the relationship of luminosity with circumference and filling factor, which gives a way to evaluate the choice of geometry, and compare the nominal performances of CEPC-SPPC, LHC and FCC.
基金Supported by National Natural Science Foundation of China(11175192)
文摘In this paper we will show a cavity and higher order mode （HOM） coupler designing scheme for the Circular Electron-positron Collider （CEPC） main ring. The cavity radio frequency （RF） design parameters are shown in this paper. The HOM power is calculated based on the beam parameters in the Preliminary Conceptual Design Report （Pre-CDR）. The damping results of the higher order modes （HOMs） and same order modes （SOMs） show that they reach the damping requirements for beam stability.
基金JG is Supported by an International Postdoctoral Exchange Fellowship Program between the Office of the National Administrative Committee of Postdoctoral Researchers of China(ONACPR)DESY.YYL is Supported by Hong Kong PhD Fellowship(HKPFS)and the Collaborative Research Fund(CRF)(HUKST4/CRF/13G)
文摘It is difficult to measure the WW-fusion Higgs production process （e＋e-→vvh） at a lepton collider with a center of mass energy of 240-250 GeV due to its small rate and tile large background from the Higgsstrahlung proeess with an invisible Z （e＋e- → hZ,Z-4→vv）. We construct a modified recoil mass variable, mprecoil, defined using only the 3-momentum of the reconstructed Higgs particle, and show that it can separate the WW-fusion and Higgsstrahhlng events bettcr than the original recoil mass variable m recoil. Consequently, the variable can be used to improve the overall precisions of the extracted Higgs couplings, in both the conventional framework and the effective-field-theory framework. We also explorc the application of the mprecoil variable in the inclusive cross section mcasurements of the Higgsstrahlung process, while a quantitive analysis is left for future studies.
基金Supported by National Natural Science Foundation of China(11265003,U1431109,11205240)State Key Laboratory of Particle Detection and Electronics
文摘In this work, we study the response of a single layer Thick Gaseous Electron Multiplier （THGEM） detector to p/π＋ at the E3 line of the Beijing Test Beam Facility. The THGEM detector drift gap used in this study is 4 mm, and the gain of the detector operated in Ar＋3% iC4H10 is about 2000. p/π＋ particles at momenta between 500 MeV/c and 1000 MeV/c are distinguished by a Time Of Flight system. Our results show that at the measured momenta, detection efficiencies for p are from 93% to 99%, and for π＋ in the range of 82%-88%. Meanwhile, simple Geant4 simulations also have been done, and are consistent with the amplitude spectra of the beam test results. We preliminarily study the feasibility of the THGEM detector as a sampling element for a Digital Hadronic Calorimeter （DHCAL）, which may provide support for the possible application of a THGEM detector in the Circular Electron Positron Collider （CEPC） HCAL.
基金Supported by National Natural Science Foundation of China(11475183)the Key Research Program of Frontier Sciences,CAS,(Y7292610K1)
文摘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.
