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Study of beamstrahlung effects at cepc

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Chinese Physics C 2016年第5期40卷 1-6页

作者：修青磊朱宏博岳腾娄辛丑 State Key Laboratory of Particle Detection and Electronics Beijing 100049China Institute of High Energy Physics CASBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China University of Texas at Dallas RichardsonTX 75080-3021USA

The discovery of a 125 GeV Higgs boson at the LHC marked a breakthrough in particle physics. The relative lightness of the new particle has inspired consideration of a high-luminosity Circular Electron positron Collider （cepc） as a Higgs Factory to study the particle＇s properties in an extremely clean environment. Given the high luminosity and high energy of the cepc, beamstrahlung is one of the most important sources of beam- induced background that might degrade the detector performance. It can introduce even more background to the detector through the consequent electron-positron pair production and hadronic event generation. In this paper, beamstrahlung-induced backgrounds are estimated with both analytical methods and Monte Carlo simulation. Hit density due to detector backgrounds at the first vertex detector layer is found to be -0.2 hits/cm2 per bunch crossing, resulting in a low detector occupancy below 0.5%. Non-ionizing energy loss （NIEL） and total ionizing dose （TID）, representing the radiation damage effects, are estimated to be -1011 1 MeV neq/cm2/yr and --300 kRad/yr, respectively.

关键词： cepc beamstrahlung pair production detector backgrounds radiation damage

Testing B-violating signatures from exotic instantons in future colliders

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Chinese Physics C 2017年第9期41卷 19-26页

作者： Andrea Addazi Xian-Wei Kang Maxim Yu. Khlopov Dipartimento di Fisica Universith di L'Aquila 67010 Coppito AQ and LNGS Laboratori Nazionali del Gran Sasso 67010 Assergi AQ Institute of Physics Academia Sinica Taipei 115 Institute for Advanced Simulation Jiilich Center for Hadron Physics and Institut fiir Kernphysik Forschungszentrum Jiilich D-52425 Jiilich Centre for Cosmoparticle Physics Cosmion National Research Nuclear University MEPHI (Moscow Engineering Physics Institute) Kashirskoe Sh. 31 Moscow 115409 APC laboratory 10 rue Alice Domon et Leonie Duquet 75205 Paris Cedex 13

We discuss possible implications of exotic stringy instantons for baryon-violating signatures in future colliders. In particular, we discuss high-energy quark collisions and A- transitions. In principle, the A-A process can be probed by high-luminosity electron-positron colliders. However, we find that an extremely high luminosity is needed in order to provide a （somewhat） stringent bound compared to the current data on NN→ππ,KK. On the other hand, （exotic） instanton-induced six-quark interactions can be tested in near future high-energy colliders beyond LHC, at energies around 20-100 TeV. The Super proton-proton Collider （SppC） would be capable of such measurement given the proposed energy level of 50-90 TeV. Comparison with other channels is made. In particular, we show the compatibility of our model with neutron-antineutron and NN→ππ, KK bounds.

关键词： cepc SppC exotic instanton baryon number violation

Optimizing Higgs factories by modifying the recoil mass

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Chinese Physics C 2018年第3期42卷 18-32页

作者：顾嘉荫李英英 DESY Center for Future High Energy Physics Institute of High Energy Physics19B Yuquan LuChinese Academy of Sciences Department of Physics The Hong Kong University of Science and Technology

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.

关键词： cepc ILC Higgs

Optimization of the scintillator units for the cepc scintillator-tungsten ECAL

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Radiation Detection Technology and Methods 2020年第1期4卷 39-45页

作者： Bing Zhao Mingyi Dong Ming Zhou Zhigang Wang Hang Zhao Yazhou Niu Tao Hu Shujun Zhao Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Particle Detection and Electronics Beijing 100049China University of Chinese Academy of Sciences Beijing 100049China University of Science and Technology of China Hefei 230026China Zhengzhou University Zhengzhou 450001China

Background The circular electron positron collider(cepc)was proposed as a future Higgs/Z factory.A sampling calo-rimeter with scintillator-tungsten sandwich structure(ScW)is selected as one of the electromagnetic calorimeter(ECAL)options.Its active layers consist of plastic scintillator strip units with a thickness of 2 mm and a size of 5×45 mm2,read out by silicon photomultipliers(SiPM).Purpose The light output has non-uniformity along the length direction of the scintillator strip,which affects the resolution of the ScW ECAL.It is necessary to control the non-uniformity to a low level.Methods We present the optimization of the scintillator units to improve the uniformity of the light output,including the light output distribution of the scintillator strips with different SiPM coupling configurations,and the impact of the coupling groove shape and dimension on the light output uniformity.Results and conclusion The results show that the non-uniformity of the scintillator unit with a runway-shaped coupling groove at the bottom-center of the strip can achieve 4%without reduction in the light output.Compared to the case of non-uniformity before optimization,the optimized uniformity improves the boson mass resolution about 23%based on the reconstruction of Higgs→γγ,which is comparable to the perfect homogeneous case.

关键词： cepc ECAL SiPM Uniformity Scintillator

Characterization of the first prototype CMOS pixel sensor developed for the cepc vertex detector

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Radiation Detection Technology and Methods 2019年第3期3卷 222-230页

作者： L.J.Chen H.B.Zhu X.C.Ai M.Fu R.Kiuchi Y.Liu Z.A.Liu X.C.Lou Y.P.Lu Q.Ouyang X.Shi J.Tao K.Wang N.Wang C.F.Yang Y.Zhang Y.Zhou institute of high energy physics chinese academy of sciences19b yuquan roadshijingshan districtbeijingchina university of chinese academy of sciences no.19(a)yuquan roadshijingshan districtbeijingchina state key laboratory of particle detection and electronics 19b yuquan roadshijingshan districtbeijingchina deutsches elektronen-synchrotron(desy) notkestraße 8522607 hamburggermany university of science and technology of china no.96jinzhai road baohe districthefeianhuichina ocean university of china no.238 songling roadqingdao 266100china

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.

关键词： CMOS pixel sensor cepc Power consumption Diode geometry Charge-over-capacitance ratio

cepc Higgs物理重味标定的关键探测器原型芯片外围数字电路的研究

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CEPC Higgs物理重味标定的关键探测器原型芯片外围数字电路的研究

作者：王俊超中国科学技术大学

学位级别：硕士

2012年,欧洲核子中心(CERN)在大型强子对撞机(Large Hadron Collider,LHC)实验中发现了希格斯玻色子(Higgs Boson),粒子物理领域进入了一个新的时代。通过精确测量希格斯粒子的特性来探寻超越标准模型的新物理成为了粒子物理领域的热点... 详细信息

2012年,欧洲核子中心(CERN)在大型强子对撞机(Large Hadron Collider,LHC)实验中发现了希格斯玻色子(Higgs Boson),粒子物理领域进入了一个新的时代。通过精确测量希格斯粒子的特性来探寻超越标准模型的新物理成为了粒子物理领域的热点话题。基于此,我国科学家提出了环形正负电子对撞机(Circular Electron-Positron Collider,cepc)计划,用于产生大量的希格斯粒子以供研究。目前cepc计划仍在初步研究中,这是中国基础物理领域的一场机遇。希格斯粒子极其不稳定,在产生后会迅速衰变,不同衰变道的分离对于希格斯粒子的研究十分重要,这需要高分辨率的顶点探测器对衰变产物进行高效的味道标定。cepc中的顶点探测器,是最接近反应点的探测器,需要高空间分辨率、快速的数据读出率、低物质量以及良好的抗辐照性能。单片式有源像素传感器(Monolithic Active Pixel Sensors,MAPS)正是能够满足上述要求的一项技术。国外的硅像素探测器发展较为迅速,我国在技术水平上与国际前沿还有较大的差距。目前我国自主研发的硅像素探测器芯片都无法满足cepc顶点探测器的需求,但这是我国硅基芯片发展必须要渡过的一关。在MAPS芯片中,读出速度决定了探测器芯片对粒子的探测能力,一个快速的电路读出架构是MAPS芯片完成探测任务的保障,这也是我国自主研发硅像素芯片必须掌握的一项关键技术。本文以cepc顶点探测器原型芯片的研发为背景,从数字读出的角度进行研究,以数据读出速度为重心,寻求能满足cepc顶点探测器需求的读出架构。本文的主要工作是参与到cepc顶点探测器原型芯片MIC5的设计,提出了一种可能应用于cepc顶点探测器MAPS芯片的外围数字电路结构,对该结构进行了分析,并基于TowerJazz 180nm CMOSImage Sensor工艺在专用集成电路(ASIC)上实现了该结构,最终数据读出速度达到800 Mbps,功耗约80 mW。本文的主要工作体现在以下几个方面:1、目前国内外针对MAPS芯片外围电路的数字读出架构还没有成熟、系统的理论研究,本文自主设计了无需片上RAM的外围读出架构,设计了基于FIFO的两级缓存结构,并分析了其可行性及FIFO深度的设置与像素击中率和读出速度的关系,同时设计了一种全新的数据管理和数据帧结构,既保证了被击中像素的信息能完整地被记录和传递,又能够与芯片的数据读出速率相匹配,达到了当前情况的最优解。2、本文基于TowerJazz 180 nm CMOS Image Sensor工艺,按照数字集成电路设计流程,完成了外围数字电路物理版图的设计,且通过版图物理验证、版图后仿真等方式验证了 MIC5外围数字电路的功能和性能。3、本文设计了基于FPGA的MIC5外围数字电路硬件测试系统,进行了芯片SPI控制、数据读出等功能的测试,验证了 MIC5外围数字电路设计的正确性和可操作性,为将来的芯片测试打下了基础。

关键词： cepc MAPS 外围电路综合版图

Preliminary study on protection of synchrotron radiation damage in cepc main ring

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Radiation Detection Technology and Methods 2018年第1期2卷 65-74页

作者： Haoyu Shi Yadong Ding Qinbing Wang Zhongjian Ma Institute of High Energy Physics CASBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Background The Circular Election–Positron Collider has been proposed by Institute of High Energy Physics(IHEP,CAS).The beam in the main ring with energy up to 120 GeV would produce intense synchrotron radiation(SR)with photon energy up to several MeV.Without shielding,this radiation would be harmful to the accelerator components.Purpose To clarify the radiation damage,analyze the source of SR,and design the shielding system to protect the accelerator.Methods The theoretical formula has been used to estimate the spectrum and distribution of SR.Several ways of designing or shielding vacuum chamber with different geometries and various materials are put forward to protect sensitive facility components.The Monte Carlo program FLUKA has been introduced to calculate cumulative dose and heat deposition in all designing cases.Results The SR in cepc main ring would be harmful to the coil used in dipole magnets.The design based on LEP with aluminum and lead would need 23 mm lead to make the coil safe.The design based on LEP with copper would need 28 mm of outer copper.And the copper chamber and lead shield design would need 16 mm of Lead.Conclusion The theoretical formula has been used in source generation of Monte Carlo program to get the distribution of SR in cepc main ring.The program was also used to simulate SR problems in the vacuum chamber with designs of different geometries and materials.Among these designs,the elliptical pipe with lead shield is preferred in cepc.

关键词： cepc Monte Carlo simulations Synchrotron radiation Vacuum chamber Cumulative dose Radiation shielding

Studies of detector cells for a hadronic calorimeter based on plastic scintillators

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Radiation Detection Technology and Methods 2018年第1期2卷 151-156页

作者： Zhe Wu Dongmei Xia Zhigang Wang Hang Zhao Peng Hu Wei Hu Tao Hu Jiechen Jiang Boxiang Yu College of Power Engineering Chongqing UniversityChongqing 400044China State Key Laboratory of Particle Detection and Electronics Beijing 100049China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

In this paper,we study variations of a plastic scintillator tile coupled to silicon photomultiplier via a dome-shaped cavity originally developed in the CALICE collaboration.Four kinds of plastic scintillator detector cells with different sizes based on the structure were studied for applications in analog readout highly granular hadronic calorimeter(AHCAL)in future circular electron positron collider(cepc)project.The responses to cosmic rays of the detector cells could reach 33.89 p.e./MIPs(minimum ionizing particles).The good results of both response uniformity and MIP detection efficiency(above 95%)show that the detector cells with larger sizes(40×40×3 and 50×50×3 mm^(3))could provide an option for AHCAL detector cells of cepc detectors.

关键词： cepc AHCAL Plastic scintillator Cosmic-ray test Response uniformity

Cavity fundamental mode and beam interaction in cepc main ring

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Radiation Detection Technology and Methods 2018年第1期2卷 113-121页

作者： Dianjun Gong Jie Gao Jiyuan Zhai Dou Wang Institute of High Energy Physics BeijingChina University of Chinese Academy of Sciences 100049 BeijingChina

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.

关键词： cepc Main ring Fundamental mode Beam loading Phase shift CBI