中国物理学会高能物理分会第十四届全国粒子物理学术会议定于2024年8月14日至18日在青岛召开。会议由中国物理学会高能物理分会主办、山东大学承办。会议期间将同期举办第十三届“晨光杯”优秀论文评选活动,高能物理战略研讨会也将在大会召开之前于2024年8月13日召开。
现将相关事宜通知如下。
一、会议主要内容:
(一)交流国内外高能物理和粒子物理领域最新研究成果和进展。
本次大会将按照以下五个研究领域来组织报告,并在每个领域中包含实验和理论研究进展:
1. TeV物理和超出标准模型新物理
2. 强子物理与味物理
3. 高能重离子物理
4. 中微子物理、粒子天体物理与宇宙学
5. 粒子物理实验技术
具体的报告安排及日程将在下一轮通知和会议网站中发布。
大会组委会诚挚邀请各位同仁参加本届会议,并积极提交学术报告摘要。
(二)第十三届“晨光杯”青年优秀论文评选。
高能物理分会每两年举办一次青年优秀论文评选。第十三届“晨光杯”青年优秀论文评选与第十四届全国粒子物理学术会议同期举办,欢迎青年科技人员积极参加评选活动,并邀请各位高能物理分会的常委和委员积极组织、推荐优秀论文参选。
参加评选活动的条件:
1. 申请人是从事高能物理(包括粒子物理理论和实验、中高能核物理、宇宙线和高能天体物理等)科研工作的35岁以下尚未获得高级科教职称的青年科研人员(即不接受已经获得教授、副教授以及同等职称的研究人员参评)。
2. 参评论文必须是申请截止日期以前,已正式发表的论文或已接受发表的论文。
3. 申请人应为参评论文的主要贡献者,且申请人及申报论文的第一单位为国内单位。
4. 参评论文正式发表时间为上届“晨光杯”评选活动截止(2022年4月30日)后正式发表的论文。
申请于2024年4月30日截止(以电子邮件接收时间为准)。符合条件的申请人将申报论文、《申请—推荐表》及所需之两位《专家评阅意见表》(已正式发表的论文不必填写此表)的电子版文件(表格下载地址: https://indico.ihep.ac.cn/event/21331/),在截止日期前发送至学会秘书处(邱雯:qiuw@ihep.ac.cn)。学会秘书处将对申请人和所申报的论文进行资格审查,并根据申报论文的专业内容,组织专家初评。进入终评论文的作者将在本届全国高能物理大会上报告论文成果,经终评委员会评委无记名投票遴选出“晨光杯”青年优秀论文。
“晨光杯”将设一等优秀论文1-3篇,二等优秀论文3-6篇。高能物理分会将对优秀论文作者颁发入选证书和物质鼓励。
诚挚邀请各位老师同仁在征集范围内积极组织、推荐论文参加。
二、会议有关事项:
1.会议时间:2024年8月14日-8月18日,8月13日报到,8月18日离会。
高能物理战略研讨会将于2024年8月13日召开,拟参加战略研讨会的老师敬请8月12日报到。
2. 会议地点:青岛海泉湾皇冠假日酒店
3. 住宿酒店:青岛海泉湾皇冠假日酒店、 青岛蓝谷国际酒店
4、报到及注册地点:上述入住酒店的一楼大堂,会议开始后在会场注册。
5. 会议注册:
(1)注册费:粒子物理大会:教师2000元/人,学生和博士后1200元/人。会议协助安排食宿,费用自理,可为参会家属提供会议用餐,收费标准为1000元/人。战略研讨会注册费:500元/人。
(2)会议注册:
请使用中文进行注册,并确保姓名、单位信息、税号等信息的准确,以便于开发票。
(3)注册截止时间:2024年5月31日;报告摘要提交截止时间:2024年6月30日。
鉴于八月份为青岛旅游旺季,请拟参会人员务必按时注册和提交报告提交摘要。
6. 地方会务组联系人:
尹 娜(会务秘书) 电话: 0532-58631321 (办公室), Email: yina@sdu.edu.cn
黄性涛(会务协调人)电话: 0532-58631310 (办公室), Email: huangxt@sdu.edu.cn
7. 高能物理分会秘书处联系人:
邱 雯(分会秘书) 电话:010-88235843(办公室), Email:qiuw@ihep.ac.cn
赵 强(分会秘书长)电话:010-88236578(办公室), Email:zhaoq@ihep.ac.cn
各位同事:
按照前三轮通知安排,中国物理学会高能物理分会第十四届全国粒子物理学术会议将于 2024 年 8 月 13 日至 18 日在青岛召开。目前会议各项筹备工作基本准备就绪,会议日程、交通服务以及其它注意事项详见会议手册或本网站相关栏目。
为了方便联系,会务组已建立微信群,详见下方二维码(或联系地方组委会联络人),请各位参会同事及时加群,后续事宜我们将会在群里通知。
如遇其它问题,也请随时与我们联系。
期待与大家在青岛相见!
山东大学会议地方组委会
2024年8月2日
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
会议资助:
山东大学、中国高等科学技术中心、国家自然科学基金委员会、山东省科学技术厅、中华人民共和国科学技术部、山东大学科学技术研究院
赞助商:
合肥中科采象科技有限公司、北京华恒鑫达科技发展有限公司、北京科创鼎新真空技术有限公司、控创(北京)科技有限公司、北京中检维康电子技术有限公司
A non-extensive (3+1)-dimensional hydrodynamic model for multi-particle production processes, NEX-CLVisc, is developed in the framework of the CLVisc package where the viscous corrections are turned off. It is based on non-extensive statistics and assumes that non-extensive effects exist in the initial conditions, the equation of state and the hadron kinetic freeze-out procedure. The model is then applied to investigate the pseudo-rapidity ($\eta$) distribution, the transverse momentum ($p_{\rm T}$) spectra and the $p_{\rm T}$-differential elliptic flow ($v_2$) of charged particles in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV and 5.02 TeV. It is found that the model can reasonably reproduce the $\eta$ distribution and the charged-particle spectra in a $p_{\rm T}$ range up to 6–8 GeV/c. When compared with the ideal hydrodynamic model, the $p_{\rm T}$-differential $v_2$ of charged particles is reduced in the NEX-CLVisc model, which is similar to that observed in the viscous hydrodynamic model. Moreover, the extension of the applicable range for $p_{\rm T}$-differential $v_2$ is not as large as that indicated by the particle $p_{\rm T}$ spectra.
$\phi$ has relatively small hadronic interaction cross sections and it can be used to study the properties of nuclear medium at the early stage. The recombination model indicates that the $\Omega/\phi$ ratio will be enhanced at low and medium transverse momentum $(p_{\text{T}})$, where thermal strange quarks dominate the production of $\Omega$ and $\phi$ in the QGP. Therefore, the multi-strange baryon-to-meson ratio $\Omega({sss})/\phi({s\bar{s}})$ is proposed to be a sensitive probe for studying the onset of deconfinement. Because the STAR Beam Energy Scan Phase ΙΙ (BES ΙΙ) program has 10 times larger data size than BESΙ and explore the QCD phase diagram in a region which may cover the potential critical point, it offers us a great opportunity to investigate collision energy and system size dependence of $\phi$ production in heavy-ion collisions.
In this report, we present new measurements on $p_{\text{T}}$ spectra, centrality dependence of $\phi$ production yields (dN/dy), resonance to non-resonance yield ratio $(\phi/K^{-})$, nuclear modification factor $(R_{\text{CP}})$, the rapidity spectra and $\Omega({sss})/\phi({s\bar{s}})$ ratio in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6 and 19.6 GeV. Physics implications of these measurements will be discussed.
In this study, the canonical formulation of the spin hydrodynamics of Dirac fermions is examined within a power counting scheme, where the spin variables are considered to be at the same order as the conventional hydrodynamic variables. An entropy-current analysis with a general spin potential reveals the importance of incorporating both the three components of spin density associated with spatial rotation symmetry and the other three components linked to boost symmetry to uphold the entropy principle. It is found that the boost variables have to be included in the stress-energy tensor, along with a totally antisymmetric spin tensor for Dirac fermions. The constitutive relations is chosen to be related to the phenomenological formulation of spin hydrodynamics by pseudogauge transformation. Upon linear-mode analysis, it is observed that the spin and hydrodynamic modes in this canonical formulation exhibit the same dispersion relations as the phenomenological formulation up to the relevant order.
Measurements of heavy flavor quark correlations in heavy-ion collisions are crucial to understand the flavor dependence of quark energy loss mechanisms in hot and dense QCD matter. In addition to the heavy-ion collisions, experimental measurements of heavy flavor correlations in p+p collisions can provide insights into the contributions of perturbative and non-perturbative QCD processes to the correlation functions and further help in interpreting correlation measurements in heavy-ion collisions. In this study, we investigate charm quark and D-meson correlations using PYTHIA Event Generator and a multiphase transport model (AMPT). By introducing a transport model approach with partonic rescatterings connecting to the initial conditions provided by PYTHIA event generator, effects of the partonic collisions on the charm azimuthal correlations in relativistic p+p collisions are investigated. It is found that the partonic collisions during the lifetime of the partons enhance the away-side correlation and suppress the near-side correlation, whereas hadronization and final state hadronic interactions bring tiny effect to the azimuthal correlations. These findings indicate that partonic effect plays an important role in the azimuthal correlations of heavy flavor particles in relativistic p+p collisions. Our study offers insights into the future experimental measurements of heavy quark correlation at RHIC and LHC energies.
The Phi meson and Omega baryon provide unique probes of the properties of the quark-gluon plasma (QGP) at hadronization in relativistic heavy-ion collisions. Using the quark recombination model with the quark phasespace information parameterized in a viscous blast wave, we perform Bayesian inference of the shear and bulk viscosities of the QGP at hadronization with a temperature of T ≈ 160 MeV by analyzing the phi and Omega data in Au+Au collisions at √sNN = 19.6–200 GeV and Pb+Pb collisions at √sNN = 2.76 TeV, corresponding to a baryon chemical potential variation from μB ≈ 0 to 200 MeV. We find that the shear viscosity to enthalpy ratio of the QGP at hadronization decreases as μB increases, while the corresponding specific bulk viscosity is essentially constant for μB < 200 MeV. Our results suggest that the QGP at hadronization (T ≈ 160 MeV) with finite baryon density is more close to perfect fluid than that with zero baryon density.
Measurements of charm-strange meson and charm-baryon production in pp and heavy-ion collisions at the LHC are fundamental to investigate the charm-quark hadronisation across collision systems.
In this contribution, the final results of the ALICE Collaboration on the production of strange ($\mathrm{D_s}^+$ , $\Xi_\mathrm{c}^{0,+}$, $\Omega_\mathrm{c}^0$) and non-strange ($\mathrm{D}^0$ , $\mathrm{D}^+$, $\mathrm{D}^{*+}$ , $\Lambda_\mathrm{c}^+$, $\Sigma_\mathrm{c}^{0,+,++}$) charm hadrons in pp, p–Pb and Pb–Pb collisions collected in Run 2 by the ALICE experiment are shown.
The production measurements of $\mathrm{D_s}^+$ mesons are compared to those of non-strange mesons, and the comparison between the measured baryon-to-meson ratios with novel theoretical calculations will be discussed. To conclude, the first studies of charm-hadron reconstruction using the large data sample of pp collisions at √s = 13.6 TeV harvested from the start of LHC Run 3 are presented.
Energy correlators have shed light on the properties of QCD splitting in vacuum, which should be modified due to nuclear effects in a deconfined QCD matter such as the quark-gluon plasma. By employing the recently developed multi-stage jet evolution framework JETSCAPE, we have investigated the nuclear modification of energy correlators for inclusive jets in heavy-ion collisions. We find energy correlators are significantly influenced by the splitting behaviors in the small angle region, and by the medium response in the large angle region. We also provide the theoretical predictions of energy correlators for ALICE and CMS measurements.
In this talk, We will present a theoretical study on the production of the heavy-flavour decay lepton (HFL) in high-energy nuclear collisions at the LHC. The pp-baseline is calculated by the FONLL program, which matches the next-to-leading order pQCD calculation with the next-to-leading-log large-$p_T$ resummation. The in-medium propagation of heavy quarks is driven by the modified Langevin equations, which consider both the elastic and inelastic partonic interactions. We propose a method to separate the respective influence of the five factors, such as pp-spectra, the cold nuclear matter (CNM) effects, in-medium energy loss (E-loss), fragmentation functions (FFs), and decay channels, which may contribute to the larger $R_{AA}$ of HFL $\leftarrow b$ compared to that of HFL $\leftarrow c$ in nucleus-nucleus collisions. Based on quantitative analysis, we demonstrate that different decay channels of charm- and bottom-hadrons play an essential role at $p_T<$5 GeV, while the mass-dependent E-loss dominates the higher $p_T$ region. It is also found that the influences of the CNM effects and FFs are insignificant. At the same time, different initial pp-spectra of charm and bottom quarks have a considerable impact at $p_T>$ 3 GeV. Furthermore, we explore the path-length dependence of jet quenching by comparing the HFL $R_{AA}$ in two different collision systems. Our investigations show smaller HFL $R_{AA}$ in Pb+Pb than in Xe+Xe within the same centrality bin, consistent with the ALICE data. The longer propagation time and more effective energy loss of heavy quarks in Pb+Pb collisions play critical roles in the stronger yield suppression of the HFL compared to that in Xe+Xe. In addition, we observe a scaling behaviour of the HFL $R_{AA}$ in Xe+Xe and Pb+Pb collisions.
At leading order in QCD coupling constant, we compute the energy loss per traveling distance of a heavy quark $dE/dz$ from elastic scattering off thermal quarks and gluons at a temperature $T$, including the thermal perturbative description of soft scatterings ($-t<-t^{\ast}$) and a perturbative QCD-based calculation for hard collisions ($-t>-t^{\ast}$). Within this soft-hard factorization model, we find that the full results of $dE/dz$ show a mild sensitivity to the intermediate cutoff $t^{\ast}$, supporting the validity of the soft-hard approach within the temperature region of interest. We re-derive the analytic formula for $dE/dz$ in the high-energy approximation, $E_{1}\gg m^{2}_{1}/T$, where $E_{1}$ is the injected heavy quark energy and $m_{1}$ is its mass. It is realized that the soft logarithmic contribution, $dE/dz\propto ln(-t^{\ast}/m^{2}_{D})$, arises from the $t$-channel scattering off thermal partons,
while the hard logarithmic term, $dE/dz\propto ln[E_{1}T/(-t^{\ast})]$, stems from the $t$-channel scattering off thermal partons, and the one $dE/dz\propto ln(E_{1}T/m^{2}_{1})$ comes from the $s$- and $u$-channel scattering off gluons. The sum of these contributions cancels the $t^{\ast}$-dependence as observed in the full result. The mass hierarchy is observed as $dE/dz(charm)>dE/dz(bottom)$.
Our full results are crucial for a better description of heavy quark transport in QCD medium, in particular at low and moderate energy. We also calculate the energy loss by imposing Einstein's relationship. The related results appear to be systematically larger than that without imposing Einstein's relationship.
The longitudinal spin transfer represents the probability density of producing longitudinally polarized hadrons from longitudinally polarized quarks or circularly polarized gluons. It thus was usually measured in polarized reactions or high-energy collisions where weak interaction dominates. In this work, we propose the dihadron polarization correlation as a novel probe of this quantity. Such an observable does not require the fragmenting partons to be polarized and therefore can be measured in the currently available experimental facilities, such as Belle, RHIC, Tevatron, and the LHC. We make quantitative predictions for these experiments. In light of the data already harvested, the experimental investigation of this observable provides more opportunity for the quantitative study of the longitudinal spin transfer. In particular, the measurements in $pp$ collisions can significantly constrain the fragmentation function of a circularly polarized gluon.
Furthermore, by applying this approach to the relativistic heavy-ion collisions, we can investigate the spin effect in the context of jet quenching.
References
[1] Hao-Cheng Zhang, Shu-Yi Wei; Probing the longitudinal spin transfer via dihadron polarization correlations in unpolarized $e^+e^-$ and $pp$ collisions; Phys.Lett.B 839 (2023) 137821.
[2] Xiaowen Li, Zhao-Xuan Chen, Shanshan Cao, Shu-Yi Wei; Correlations of dihadron polarization in central, peripheral, and ultraperipheral heavy-ion collisions; Phys.Rev.D 109 (2024) 014035.
In-jet production is a useful tool to separate the contribution from the hard processes and the underlying events. In this letter, we find the in-jet requirement enhances the heavy flavor baryon-to-meson ratio more when a color re-connection mechanism (CR mode2) describes hadronization in p+p, which is opposite to the light flavor case. It indicates the hard process contribution alone will lead to an enhancement of the heavy flavor baryon-to-meson ratio using CR mode2 while the light flavor baryon-to-meson ratio enhancement is mainly coming from underlying events. When the hot and dense medium is involved in Pb+Pb collisions, the in-jet $\rm \Lambda_c^+/D^0$ ratio also enhances at intermediate $\rm p_T$ when a coalescence + fragmentation hybrid approach is used to describe in-medium hadronization. To distinguish the mechanism of two types of enhancement, $\rm \Lambda_c^+/D^0$ ratios as functions of particle-jet axis distances $\rm R$ for different jet $\rm p_T$ intervals are also been computed. The results indicate the enhancement described by the color re-connection mechanism is dominated by low $\rm p_T$ ($< 2$ GeV) enhancement and that described by a coalescence mechanism is dominated by intermediate $\rm p_T$ ($2-4$ GeV) enhancement. The detailed measurement of the in-jet $\rm \Lambda_c^+/D^0$ ratios in p+p collisions at lower $\rm p_T$ will help constrain the baryon hadronization mechanism in the small system.
The measurement of jets recoiling from a trigger hadron provides unique probes of medium-induced modification of jet production. Jet deflection via multiple soft scatterings with the medium constituents or single-hard Moli`ere scatterings off quasi-particles in the medium are expected to modify the azimuthal correlation between the trigger hadron and recoiling jet. The $R$-dependence of recoil jet yield also probes jet energy loss and intra-jet broadening. In this talk, we present measurements of the semi-inclusive distribution of charged jets recoiling from a trigger hadron in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ALICE. We employ precise, data-driven subtraction of the large uncorrelated background contaminating the measurement in Pb-Pb collisions, enabling the exploration of medium-induced modification of jet production and acoplanarity over a wide phase space, including the low jet $p_\mathrm{T}$ region for large jet resolution parameter $R$. Hadron-jet acoplanarity in pp collisions will also be presented, which provides a sensitive test of pQCD calculations and a crucial data reference for in-medium jet deflection studies in Pb-Pb collisions. We observe that the jet yield at low $p_\mathrm{T}$ and at large azimuthal angle between the trigger hadron and jet is significantly enhanced in Pb-Pb collisions to pp collisions. Comparison to theoretical calculations incorporating jet quenching will also be discussed.
Particles associated with the jet will be deflected from their initial direction due to the scatterings with the thermal partons flowing in the QGP fluid. Such deflections depend on the energy of the jet, the local energy gradient, and the local flow velocity. In general, the soft particles will drift towards the direction of the flowing medium, away from the center of the jet cone where the hard particles are located, leading to an intra-jet asymmetry coupled with flow, which can be used to extract the properties of the QGP medium. In this work, we first calculate the intra-jet asymmetry distribution in both transverse and longitudinal directions and investigate their dependence on path length, viscosity, and jet multiplicity. Such asymmetry is also observed in the jet chemical structure. We then extract the average radial flow velocity distribution via the intra-jet asymmetry distribution and compared it with the hydrodynamic simulation results. Our approach can be further used to localize the initial production position of the jet without specified requirements of the jet direction. As we apply jet localization to gamma-jet and dijet events, we find an improvement in the localization accuracy of dijet events due to the interplay between QGP flow and the diffusion wake induced by the backside jet.
高能环形正负电子对撞机(Circular Electron Positron Collider, CEPC)的顶点探测器,对于重味夸克重建与分辨至关重要。为了实现高精度的物理测量,对内层顶点探测器的物质量、空间分辨率、读出速度以及功耗等方面的性能提出了严苛的要求。为研制顶点探测器原型样机,研发团队研发一款名为TaichuPix的单片式像素探测器芯片,旨在实现优于5 微米的空间分辨率,抗总剂量辐照能力超过1 Mrad,并兼顾 CEPC 顶点探测器的最高击中率需求。TaichuPix芯片基于180 nm CMOS工艺研制,目前已经完成两版小规模原型芯片(25 mm2)和一版全尺寸原型芯片(~ 4 cm^2)的设计和验证。本报告将介绍 TaichuPix芯片的设计方案和全尺寸芯片的测试结果。项目组基于全尺寸TaichuPix芯片研制了6层束流望远镜系统,并在DESY电子束流上开展了芯片的束流测试,经验证单芯片可以达到优于5微米的空间分辨率,并同时实现高于99%的探测效率。本报告还将介绍探测器模块(ladder)读出电子学的设计及测试结果。最后介绍第一版3层双面桶状顶点探测器原型样机的设计和安装,及其电子束流测试的结果。
位于磁场上游的径迹探测器Upstream Tracker(UT)是LHCb探测器重要组成部分,对提高长寿命粒子重建效率和长径迹匹配速度至关重要。为发掘高亮度LHC上重味物理研究潜力,LHCb计划在2033年前后进行二期升级,以实现在$1.5 \times 10^{34} cm^{-2}s{-1}$亮度下运行的目标。现有UT须升级为颗粒度更高、抗辐照性能更强的像素型探测器。本报告将介绍目前可行的MAPS技术选项,基于CMOS的初步系统设计和探测器模拟,以及初步的性能研究。
CMOS像素探测器(CPS)已经广泛应用于粒子物理实验的带电粒子检测等领域,包括STAR实验、ALICE实验等,也是国际直线对撞机(International Linear Collider, ILC)顶点探测器方案的有力竞争者。在ILC中,大量来自背景束带电粒子在CPS中形成额外命中,增加了探测器系统的输出数据量。
研究团队拟通过研发片上集成人工神经网络的智能化CMOS像素探测器专用集成电路,实现背景束粒子命中的标记和片上筛除,完成海量数据的压缩,降低探测器系统的数据量。研究团队完成了该方案的FPGA级设计验证,开发了针对CMOS像素探测器片上集成的Clustering、特征提取等关键模块的算法及电路架构。另一方面,考虑到六边形像素几何结构在相邻像素数目等方面的优势,团队同步开展了相关的设计研究。
未来对撞机实验上通常需要大面积、高空间分辨率、良好时间分辨及抗辐照的带电径迹探测系统,如环形正负电子对撞机、LHCb升级等。高压CMOS具有良好抗辐照性能、快速电荷收集,且可利用成熟的商用CMOS工艺。本报告将介绍探索先进的55nm高压CMOS工艺、用于粒子探测传感器的研发情况。基于Low-Leakage 55nm的COFFEE1芯片达到8-9V击穿电压,并观察到对激光信号响应。基于High-Voltage 55nm的COFFEE2芯片加入了像素内放大器和比较器电路,传感器达到70V击穿电压。其他测试正在进行。
MAPS是高能物理实验中内径迹探测器重要的实现方式之一,其具有物质量低、空间分辨高等特点。兼具时间测量和能量测量功能的MAPS通常被称作5D MAPS,有利于进一步提高径迹重建效率,但也给芯片设计带来了更大的挑战。本研究面向下一代高亮度电子对撞机内径迹探测器,基于不同工艺和优化方案开展低功耗 5D MAPS的设计工作。其中在GSMC130 nm工艺下,像素单元尺寸为33.2 μm×33.2 μm,通过对多个像素单元的数字输出错位做”或”并编码的方式合并读出通道,并基于超级像素进行数据读出,从而降低数字功耗。同时,超级像素内集成500 MHz启停型VCO用于细时间计数,使时间测量精度大幅降低到2ns,且不产生额外静态功耗。外围电路包含击中信息的读出、时间戳校准、汇总、缓存、组帧、编码和高速串行化等功能。预计芯片总功耗小于60 mW/cm²。
宇宙微波背景辐射(CMB)是宇宙大爆炸后早期冷却过程产生的遗留辐射,保留了丰富的宇宙早期信息。目前CMB实验的主要观测目标已经变为极其微弱的B模式极化,在大尺度上测量CMB的B模式偏振是探测在暴涨时期产生的张量扰动(原初引力波)的最主要方式。这需要在观测中使用极低噪声等效功率的探测器。超导转变边沿探测器(Transition Edge Sensor,TES)是以超导薄膜作为温度计的一种热平衡探测器,具有极低的噪声和极高的灵敏度,是当前主流的CMB望远镜探测器。TES 探测器可探测低频、中频和高频的CMB信号,低频范围的探测主要是在40GHz附近观测。通过TES探测器来探测CMB的B模式极化,微波信号被耦合到电路当中,通过平面正交模耦合器、共面波导、微带线、滤波器、交叉器等微波链路结构,进行频率选通后传输到 TES 探测器。因此需要首先对前端微波器件进行仿真设计,通过修改微波器件的结构尺寸以及优化材料可以对其性能进行优化。我们选用了低损耗的富硅衬底重新开展了40GHz TES探测器前端微波链路的设计,对平面正交模耦合器、共面波导转微带线的阻抗匹配段、滤波器以及交叉器结构的仿真设计与计算,通过仿真优化,在30GHz~50GHz范围内,微波信号最小透过率在88%以上。通过微纳加工手段来进行TES探测器芯片的加工,芯片结构是按层生长的。我们选用定制的已长有低应力 SiNx 的硅片作为起始硅片,整个工艺流程包括9次光刻、5次干法刻蚀、1次湿法刻蚀、3次剥离、3次磁控溅射和 4次电子束蒸发。我们测量了最后整体的加工误差大约有 1um 的偏移,但由于提前预留的余量充足,所以 1um 的偏移不影响 TES 的性能。加工的重难点主要在于Nb的高选择比刻蚀、氮化硅及AlMn的生长,工艺的均匀性以及稳定性,以及最后一步的深硅刻蚀。目前采用了新的Nb线层刻蚀配方,在保证高刻蚀选择比的前提下,降低刻蚀侧壁的垂直度,使薄层金属更容易搭接,目前的工艺已经可以保证有比较高的成功率。现在在做的新一版TES加工,等最后一步深硅工艺摸索出来以后有望得到完整的符合要求的TES单像素芯片,进而可以对TES整体进行光学测试,为后续TES阵列的加工提供保证。
The Inner Tracker (ITk) of the ATLAS phase-II upgrade is aimed for function in future HL-LHC, where the particle density and radiation levels will exceed current level by a factor of ten. An all-silicon design was adopted to be faster and more spatial segmented, which requires much greater power for the front-end system. The new design is also targeting higher irradiation resistance, while the radiation length of the ITk remains reasonably low. The upgraded ITk will consist of multiple layers of silicon detectors. The silicon pixel detectors will be installed on innermost layers, while the silicon strip detectors on outer layers. This contribution focus on the strip region of the ITk. The central region (barrel) consists of 4 cylindrical shaped layers, composed of rectangular short strip (~2.5 cm) and long strip (~5 cm) sensors. The forwards region (end-cap) consists of 6 disk shaped layers per side, which covered by trapezoidal shaped strip sensors of various lengths and strip pitches.
After the completion of final design reviews, the collaboration initialized a massive prototyping program and several pre-production phases before commence the production. We will summarize the current status of ITk upgrade pre-production and production on detector components, and an emphasis on detector module assembly procedures, as well as QA/QC criteria.
The Alpha Magnetic Spectrometer (AMS-02) detector operates on the International Space Station. It performs high-precision measurements of cosmic ray composition and fluxes, and searches for antimatter and dark matter. To increase the cosmic-ray detection acceptance and improve the heavy ion identification performance, the AMS collaboration plans to add a new layer (L0) of silicon tracker on top of the existing AMS-02 detector. The new detector layer consists of 2 planes, which include 72 silicon strip detector ladders. Each ladder has 8, 10, or 12 silicon strip detector sensors (SSDs) connected in serial, producing an effective strip length of about 0.6 to 1 meter. The total sensitive area is about 8𝑚^2. All the ladders are assembled in IHEP, China.
We will present the system design of the L0 layer, the assembly procedures of ladders, and QA/QC criteria. To study the detector ladder in cosmic rays and particle beams, and calibrate the L0 tracker with particle beams before launching to space, a beam monitor has been produced. Details of the L0 layer ladder and beam monitor's performance will be described.
环形正负电子对撞机(Circular Electron Positron Collider, CEPC)探测器系统设计当前正计划完成探测器参考技术设计报告(Reference Technical Design Report,Ref-TDR)。其中,电子学-TDAQ系统计划依据本底模拟、子探测器基准设计完成总体框架设计。我们将基于通用型后端电子学、通用性触发系统设计,实现电子学-TDAQ系统整体设计。基于通用数据-光纤接口、通用抗辐照电源模块,实现前端电子学系统的框架性设计。进一步的,基于各子探测器系统的基准方案,为其提出了针对性的前端电子学设计,将实现前端无触发的全后端触发架构。本报告将介绍CEPC电子学-TDAQ系统的设计考虑、通用电子学框架,和各子探测器电子学读出方案。
时间投影室(TPC:Time Projection Chamber)可以提供精确的带电粒子三维径迹的测量,同时具有低物质量和dE/dx粒子鉴别能力,因此在高能粒子物理实验中得到广泛的应用。比如在环形正负电子对撞机(CEPC)实验中,TPC成为主径迹探测器的首选探测器。为了实现百微米的径迹分辨,TPC通常采用较小的读出焊盘,使得读出电子学密度和通道数目急剧增加。针对TPC探测器高密度读出需求,本文开展低功耗、高集成度读出电子学的研制工作,主要包括:1)一款基于65nm的低功耗波形采样和数字滤波前端ASIC芯片及可扩展读出电子学系统的研制;2)高粒子鉴别能力的像素型TPC原型读出电子学的研制。
飞行时间探测器是大型核与粒子物理实验的重要组成部分。正在建设的低温高密核物质谱仪(CEE)中,飞行时间探测器包括内部飞行时间探测器(iTOF)和端盖飞行时间探测器(eTOF),二者均采用气隙电阻板室(MRPC)技术制造。对于电子学,要求实现最高~10 ps的时间测量精度。本报告将介绍基于放大甄别结合高精度时间数字变换技术的高精度时间测量电子学系统设计、电子学与探测器联合测试以及束流测试等最新进展。
NνDEx(No Neutrino Double-beta-decay Experiment)是基于高压气体时间投影室(Time Projection Chamber,TPC)新型无雪崩放大电荷测量技术来寻找六氟化硒无中微子双贝塔衰变现象的实验。实验气腔的端盖处可容纳一个直径为0.9米的读出平面,大约由10000个Topmetal-S传感器组成。本报告将介绍其读出电子学与数据获取系统的方案,及相关芯片和电子学的研究进展。前端芯片包括Topmetal-S传感器、波形数字化与读出控制芯片。前者实现电荷收集,并集成片内电荷灵敏放大、输出缓冲、偏压设置等模块,后者完成波形数字化及芯片间的数据路由。报告也将介绍基于Topmetal-S与商用芯片的19像素前端读出电子学原型样机研制。该样机被用于芯片的集成测试及前端读出模块的方案验证。与负压离子TPC的集成测试表明,其具备径迹测量能力。目前的测试与优化则集中于电荷的收集效率、能量的测量。
即将于2025年建成的强流重离子加速器(High Intensity heavy-ion AcceleratorFacility, HIAF)上包含了一条放射性次级束分离线(HIAF FRagment Separator,HFRS)。HFRS具备普通传输线和实验线(即分离器)的双重功能,是束流能量和强度都更高的新一代放射性束流装置。该束线在多个位置上选择了一对相互倒置的Twins-TPC探测器实现粒子鉴别和束流监测。Twins-TPC作为整个束线各探测器中通道数最多、数据量最大的分系统,对读出电子学提出了高集成度、高计数率和大动态范围的要求,基于此需求,本文开展了HFRS-TPC前端读出电子学原型机系统的研制,针对高集成度、大动态范围的需求开展了技术攻关。
HFRS-TPC前端读出电子学原型机系统由ASIC板、前端板、数据汇总板和时钟扇出板构成,可以实现256路探测器信号的读出和处理。其中ASIC板基于近物所自研的一款ASIC芯片FEAM研制,实现探测器信号的放大、整形等处理;前端板基于两片高集成度ADC和FPGA,单板实现64路模拟信号的AD转换及在线处理,处理后的数据通过光纤接口传输至数据汇总板;数据汇总板单板可以实现8路光纤数据汇总,汇总后数据通过PCIe 3.0接口直接上传至服务器;时钟扇出板提供多路同步时钟,各前端板基于同步时钟工作。
在实验室对原型机系统进行测试,采用信号源模拟探测器输出。测试表明,在10fC-1PC输入动态范围内,系统积分非线性好于1%,在输入大于100fC后,系统时间分辨(sigma)好于1ns。原型机与Twins-TPC探测器原型机对接,使用激光进行测试,电子学系统工作正常。下一步,将针对高计数率需求继续开展技术攻关,满足HFRS-TPC单通道100kHz的计数率要求。
国家自然科学基金重大仪器专项低温高密核物质测量谱仪(CSR External-target Experimen,CEE)是我国第一台运行于GeV能区、完全自主研制大型核物理实验装置。CEE谱仪由若干子探测器系统构成,其中前角区带电粒子的三维径迹测量采用多丝漂移室(Multi Wire Drift Chamber,MWDC)来实现,包含3188个读出通道。CEE中的MWDC探测器对读出电子学的计数率、集成度、分辨率等指标都提出了更高的要求。基于分立元件的传统读出电子学存在功耗和集成度等弊端已无法满足要求。电子学系统包括前放模块,波形数字化模块和后端数字处理模块三部分。前放模块放置在探测器附近,基于ASIC芯片FEAM(Front-End Amplifier for MWDC)实现32通道探测器信号读出。波形数字化模块以子板形式放置于后端CPCI机箱内,基于ASIC芯片GERO(GEneral ReadOut)实现32通道探测器信号的波形数字化。后端数字处理模块设计为CPCI 6U载板,放置3个波形数字化模块,实现96通道探测器波形数据的在线时间和电荷信息提取。电子学系统实现能量分辨率好于2%@300fC,时间分辨好于500ps@300fC,并在束流测试中实现径迹残差约301±2 μm,铁源能量分辨率约22%,满足CEE实验需求
大型高能物理实验中前端探测器与后端系统之间需要一套稳定、高速、双向、抗辐照的数据传输系统,以解决前端至后端的高带宽数据发送需求,以及后端至前端的触发、时钟和控制等信息的传输需求。结合抗辐照、功耗、带宽、体积和成本等方面的综合考量,往往使用光通信系统来实现这一目标,这一解决方案在欧洲核子中心CERN的LHC实验中得到了实际应用验证。在这一套双向光纤数据传输系统中,涉及到光模块定制、抗辐照高速激光器驱动芯片、TIA跨导放大芯片、双向数据接口芯片等模块与芯片研发,在具体设计层面还涉及到高精度锁相环、时钟恢复、高速并串/串并转换、数据编解码等一些底层芯片设计。本次报告将对这一双向光通信系统的整体架构、重要芯片的功能模型以及其中部分芯片的核心设计技术进行简要介绍。
超级陶粲装置(STCF)作为下一代超高亮度正负电子对撞机,其设计亮度达到0.5×10^35 (cm)^(-2) s^(-1),高亮度设计对其探测器系统提出了新的要求与挑战。STCF电磁量能器(ECAL)需要在高事例率环境下,对粒子的能量、位置、时间等进行精确测量。针对STCF ECAL需求,开展了低噪声、高计数率、能量时间同时测量的全数字输出混合信号前端读出ASIC设计与研究,提出了针对大输入端电容的前端读出电路噪声优化方法、一种支持事件触发的可达兆赫兹的高计数率前端读出电路架构。采用标准CMOS工艺设计实现了多款原型验证芯片,测试结果表明,等效噪声电荷小于0.4fC @CIN=270pF;在模拟探测器输出信号特征下,时间测量精度优于270 ps @QIN>200fC;单通道可接收事件率大于400k,最高计数率可达4MHz/ch。
可重构ADC(time-to-digital converter, ADC) 系统具有灵活可重构与高集成度的特点,通过进行编程,便可使该系统应用于新的实验场景,因此这种电子学读出系统受到了高度的关注。我们将描述一种新型的可重构ADC系统,该系统是一种基于时间数字转换器(time-to-digital converter, TDC)的软核ADC系统。其中ADC功能是在FPGA中实现的。
在硬件设计中,基于FPGA的ADC(FPGA-ADC)只需要一个额外的电阻和一块FPGA。FPGA-ADC允许用户对其采样率进行编程,并只需通过小的修改(调整电阻值)来调整ADC的输入电压范围。这种FPGA-ADC设计具有灵活可重构和高密度的特点,可以极大减小读出电路的尺寸。
探测器部分使用了两个测试单元。每个单元包含一个1.535 mm×1.535 mm x 20 mm 硅酸钇镥晶体条和一个SiPM。FPGA-ADC是数据采集(Data Acquisition,DAQ)系统的主要组成部分。FPGA-ADC将对SiPM的原始信号执行全波形采样,在电荷积分后,得到测试单元的能量与时间分辨率。实验得到测试单元的能量分辨率约为15.3%,时间分辨率约为470 ps。
理解强相互作用物质的性质及其相结构对于我们深入认识宇宙演化和可见物质结构具有重要科学意义。近二十年来,高能重离子碰撞实验中观测到了许多间接证据表明强相互作用夸克-胶子等离子体(sQGP)的存在。因此,探索高重子密度下的量子色动力学(QCD)相结构,特别是寻找一阶相变边界和QCD临界点在相图中的位置,成为高能核物理研究的重要目标之一。从2010年到2021年,RHIC-STAR实验分两个阶段完成了能量扫描计划,收集了质心能量从200 GeV到3 GeV下金核-金核碰撞实验数据。本报告将讨论在RHIC能量扫描计划中(BES-I&BES-II)关于QCD相图和相变临界点的实验研究进展。
Phase diagram – theory
Searching the QCD critical point is one of the most important goals of the relativistic heavy-ion collisions. It is essential to build a realistic dynamical model near the QCD critical point and predict the characteristic signature induced by critical fluctuations in experimental measurements. By studying the dynamics of the conserved net-baryon density near critical point, it was found that both second- and fourth-order multiplicity fluctuations behave non-monotonically with respect to the increasing rapidity acceptance [1,2]. However, these works base on the assumption that the QGP fireball is homogenous with constant temperature and chemical potential in the coordinate space, which is not the case in realistic contexts. In this talk, we will present the dynamics of conserved net-baryon density near the critical point within the inhomogeneous temperature and chemical potential background, borrowing from hydrodynamic simulations [3]. We found that a pronounced enhancement of various orders of multiplicity fluctuations at large rapidity due to the inhomogeneous hydro background. We will also present the non-trivial behavior of multiplicity fluctuations across the freeze-out hyper surface implemented by the hydro background.
[1] Miki Sakaida, Masayuki Asakawa, Hirotsugu Fujii, Masakiyo Kitazawa. Phys.Rev.C 95 (2017) 6, 064905
[2] Grégoire Pihan, Marcus Bluhm, Masakiyo Kitazawa,Taklit Sami,Marlene Nahrgang. Phys.Rev.C 107 (2023) 1, 014908
[3] Shanjin Wu and Huichao Song. In preparation.
In this work, we extend the two-flavor Nambu--Jona-Lasinio model to one capable of exploring quark and nuclear matter consistently. With an extra term standing for quark-nucleon interactions, nucleons could automatically emerge as color-singlet three-quark entities by following a process similar to mesons. Besides the quark part in mean field approximation, both mesons and nucleons could contribute to the thermodynamic potential thus possibly give rise to quarkyonic matter beyond mean field. In the study, two kinds of "confining" couplings are adopted for the new interaction term and two different quark masses are considered for comparison. It turns out that only confined nuclear matter or deconfined quark matter is possible for all the cases at zero temperature, thus quarkyonic matter is not favored at all. Even more strictly, only the case with stronger confinement effect and a smaller quark mass admits a physical first-order phase transition from nuclear matter to quark matter around twice saturation density.
Fluctuations and correlations of conserved charges are sensitive observables to study QCD phase structure. In particular, the baryon-strangeness correlations may be used to study the change of phases in the matter created in heavy-ion collisions.
In this work, we present the measurement of baryon-strangeness correlations in Au+Au collisions from beam energy scan program at STAR. This is the first systematic analysis of baryon-strangeness correlations on the collision energy and centrality dependence including strange hadrons $K^{+}$, $\Lambda$ and $\Xi^{-}$ along with their corresponding anti-particles. Physics implications will be discussed by comparing these new results with calculations from Lattice Gauge Theory, functional renormalization group as well as a hadronic transport model.
With experimental data of DIS involving transversely polarized proton, we have calculated the 3-D charge density inside a polarized proton, which is found to have a significant non-spherical symmetry. Then we have calculated the properties of E-M field generated by a single transversely polarized proton. Based on them, the E-M field generated in small collision system p+A which involving a transversely polarized proton are studied. We find that the orientation of this E-M field has a significant dependence on the direction of transverse polarization of the proton, and the correlation function (∆γ) has also significant dependence on the angle between the reaction plane and the direction of polarization. This finding provides a new direction for probing the chiral magnetic effect (CME).
We investigate the magnetized QCD matter and chiral phase transition in a (2 + 1)-flavor Nambu–Jona- Lasinio (NJL) model at finite temperature and chemical potential by comparing the contributions from the tensor spin polarization (TSP) and anomalous magnetic moment (AMM) of quarks. On the other hand, we study the properties of the shear viscosity coefficient of quark matter near the chiral phase transition at finite temperature, chemical potential and strong magnetic field. If the magnetic field is strong enough, it will interfere with significant QCD phenomena, such as the generation of dynamic quark mass, which may affect the transport properties of quark matter. On the other hand, the chiral and deconfinement phase transitions under rotation have been simultaneously investigated in the Polyakov-Nambu-Jona-Lasinio (PNJL) model. An interesting observation has been found that the chiral phase transition is catalyzed and the deconfinement phase transition is decelerated by rotation, therefore a chiral symmetric but confined quarkyonic phase is induced by rotation, which indicates that chiral dynamics and gluon dynamics can be split by rotation.
Using AdS/CFT correspondence, we study the imaginary part of heavy quarkonia potential from thermal fluctuations in a strongly coupled plasma. We perform the analysis in a rotating deformed AdS black-hole background. It is shown that the presence of angular velocity decreases the onset of imaginary potential thus
enhancing quarkonia dissociation, in agreement with previous findings of the entropic force.
The first experimental measurement of coherent elastic neutrino-nucleus scattering (CEνNS) was successfully conducted using a CsI(Na) scintillation crystal detector. Recognizing that a higher light yield in scintillation crystal detectors correlates with greater physical sensitivity for CEνNS detection, we introduced a novel low-temperature CsI detector design employing SiPMs readout. This design capitalizes on the exceptional brightness of low-temperature CsI crystals combined with the ultra-high photon detection efficiency of SiPMs, thereby significantly improving the light yield and elevating CEνNS detection sensitivity to unprecedented levels. Positioned as a formidable contender for forthcoming CEνNS experiments, this innovative approach has been substantiated by our experimental group's development of a kilogram-scale low-temperature CsI detector [1]. This detector, notable for its leading international standards in light yield and energy resolution, serves as a preliminary proof of concept for the technical feasibility of our proposed scheme. This presentation delineates the detector scheme's characteristics, elucidating the principal prototype's performance metrics, including light yield, energy resolution, and the influence of SiPMs noise and optical crosstalk on detector performance
基于声子探测的新型荧光-热量两维读出低温晶体量热器因其高能量分辨率、独特粒子鉴别能力等优势成为寻找无中微子双贝塔衰变最有竞争力的探测技术之一。报告主要介绍新型钼酸盐晶体生长、小尺寸钼酸盐低温晶体量热器研制及10mK深冷低温读出测试、以及地面测试系统与屏蔽体设计等。
We propose to use slow muons facilities combined with cyclotron radiation detection for precision test of the weak interaction in the muon decays. Slow positive muon bunches are first injected into a cylindrical superconducting vacuum chamber with uniform strong axial magnetic fields to radially confine the muons. The positrons resulting from muon decays can be detected by their cyclotron radiation, which can be transported to low-noise electronic devices through waveguides coupled to the chamber. The decay positron's energy can be precisely measured down to eV level in the low energy region, which is sensitive to new physics effects such as Majorana neutrinos and new structures of weak interactions.
Dark SHINE is a fixed-target experiment initiative to search for light Dark Matter and mediators at SHINE (Shanghai high repetition rate XFEL and extreme light facility, being the 1st hard X-ray FEL in China) under construction targeting completion in 2026. Dark SHINE aims to search for the new mediator, Dark Photon, bridging the Dark sector and the ordinary matter. In this work and presentation, we present the idea of this new project and 1st prospective study in search for Dark Photon decaying into light dark matter. It also provides the opportunity to incorporate broader scope of BSM search ideas such as ALP, utilizing the fixed-target experiment of this type.
缪子素是正缪子和电子形成的类氢原子束缚态,正反缪子素转化实验(MACE)旨在寻找缪子素到反缪子素的自发转化过程。该过程是破坏两个单位轻子味的带电轻子味破坏(cLFV)过程,可探索TeV能标的超越标准模型的新物理。基于高流强缪子束流、高分辨率米歇尔电子谱仪、高精度正电子传输螺线管和高空间接收度的正电子谱仪,MACE有望对该cLFV过程的灵敏度从当前的最优结果进一步提高两个数量级以上。本报告将介绍MACE的设计方案及相关研发进展,包括探测器系统及各子探测器设计、缪子素产生方法和靶设计、物理灵敏度估计及其他潜在物理目标的可能性。MACE有望依托国内未来建成的缪子源取得世界领先的结果,并对超越标准模型的新物理提供更多实验依据。
正负电子对撞实验是开展粒子物理前沿研究的重要平台。高亮度意味着更多有效物理数据,实现更高的峰值亮度和积分亮度是取得新的物理突破的有效手段。触发系统是整个数据获取与处理流程的第一步。随着亮度和物理事例率的提升,实验对触发率、本底水平、触发延迟的需求也不断升高,需结合超高亮度实验环境设计并实现全新的高性能触发系统。超级陶粲装置是我国提出研究的GeV能区超高亮度正负电子对撞实验,我们基于此平台设计了新的触发系统并通过模拟、实验等方式研究其性能优化方向,以期为下一代高亮度正负电子对撞实验的触发系统开拓新的研究方向。
磁单极子作为大统一理论预言的基本粒子,在解释电荷量子化和宇宙暴胀模型等方面扮演着至关重要的角色。SCEP实验组提出了一种基于室温线圈和塑料闪烁体的符合探测手段,用以探测磁单极子。其中利用线圈探测的基本原理是通过探测磁单极子穿过线圈时产生的感应信号,这对信噪比有着严格的要求。为此,SCEP实验组提出了两种探测感应信号的方案——ADC读出方案和磁力仪读出方案。本报告将围绕这两种方案展开,介绍它们的基本结构,并详细阐述感应信号及各部分噪声的特征。为了提高信噪比,我们进行了初步的优化设计,并给出了最终的预期信噪比。
COMET实验致力于使用高强度缪子束流寻找μ-e转换这一带电轻子味破坏过程,并预期将现有结果提升两到四个数量级。COMET合作组进行了Phase-alpha阶段的预研,为了对缪子束斑的结构进行监测,我们开发了一款基于塑料闪烁光纤和硅光电倍增器的缪子束流监测探测器,对缪子束流的时间和束斑结构进行了测量。为适应后续实验中更高强度的缪子束流,探测器目前正在进行升级开发。
将报告中国组在大型强子对撞机上ATLAS实验高颗粒度时间探测器的总体研制情况。LHC将迎来高亮度升级。ATLAS实验计划研制高颗粒度时间探测器,用于压制高亮度对撞带来的堆积本底。该探测器有300万个读出通道,每个通道对单个带电粒子的时间测量精度达到30-50皮秒,可以承受高亮度LHC升级的辐照量。中国组承担了该探测器100%的LGAD硅传感器的研制(高能所承担90%份额,科大承担10%的份额),这是国产硅传感器首次在CERN对撞机实验上使用。其中,高能所LGAD传感器在与日本滨松与意大利FBK研究所竞争中胜出。赢得欧洲核子中心的国际招标的全部份额(超过1.5万个全尺寸传感器,6平方米)。另外,高能所与南大团队承担100%的外围电子学板的研制任务;高能所与科大团队承担44%探测器模块研制任务(高能所34%,科大10%);高能所与山东大学合作承担高压电源模块的研制任务;山东大学承担了柔性电缆的研制任务。
The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). A new timing detector in CMS will measure minimum ionizing particles (MIPs) with a time resolution of ~40-50 ps per hit and coverage up to |η|=3. The precision time information from this MIP Timing Detector (MTD) will reduce the effects of the high levels of pileup expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The endcap region of the MTD, called the endcap timing layer (ETL), must endure high fluences, motivating the use of thin, radiation tolerant silicon sensors with fast charge collection. As such, the ETL will be instrumented with silicon low-gain avalanche diodes (LGADs), covering the high-radiation pseudo-rapidity region 1.6 < |η| < 3.0. This talk will present the physics motivation, current status and progress made for the ETL detector.
Low- Gain Avalanche Detector (LGAD) with time resolution better than 50ps has been chosen as the sensors for HGTD project. The most important requirement of sensors for the project is radiation hardness, the sensor should collect more than 4fC charges and reach less than 50ps timing resolution at voltage(safe voltage for SEB) lower than 550V after irradiation(2.5e15neq/cm2). IHEP has developed the carbon enriched LGAD sensors, which show good radiaiton hardness.This talk will show the researches of irradiation-resistant LGAD for ATLAS HGTD.
The AC-coupled LGAD (AC-LGAD) is designed as detector with a 100% fill factor for high precision 4D-tracking. AC-LGAD can be used for the construction of time-track detectors in collider experiments such as CEPC. IHEP has also conducted extensive research on AC-LGAD. The strip-type AC-LGAD been fabricated with a lower than 0.2 P n+ layer dose to improve the spatial resolution, and different pad-pitch structures can also be fabricated and studied. This talk will also show the development of AC-LGAD for TOF out-tracker system.
LGAD是一种新型半导体定时探测器。通过优化灵敏区厚度和内部增益,可以实现几十皮秒的时间分辨率。自提出以来,LGAD技术得到了广泛的关注,发展非常迅速。目前,LGAD已经成为较为成熟的探测器技术,被大型强子对撞机(LHC)的CMS和ATLAS实验phase 2升级项目采用。采用交流感应的方式引出信号,可以实现更灵活的电极排布,减小无增益区域,在保持高时间分辨率的基础上,进一步提高位置分辨率。本报告将综述国内外LGAD探测器的研发近期的进展情况,并展望未来可能的发展方向和应用场景。
The ATLAS HGTD detector has 8032 modules, which consists of a module flex and two bare modules(LGAD sensor bump-bonded to an ASIC).About 33% of the modules will be assembled at IHEP. A high-precision robotic pick-and-place system is developed, with camera locating and robotic arm for picking and placing. This system is also used for detector unit loading, which is to place the modules into array and be glued to a PEEK support unit. Now the assembly rate reaches assemble >10 modules/day, 20modules/day in maximum. The assembled modules and detector units are tested locally to make sure they are well working. Thermal simulation and other simulation are performed to study the results from thermal and mechanical performance.
The LHC will resume operations in 2026, entering the High Luminosity (HL-LHC) era. MTD (MIP Timing Detector) is a pivotal component in the HL-LHC CMS upgrade, promising a remarkable enhancement in time resolution to 30 ps. In the part of the BTL (Barrel Timing Layer), we have formulated a comprehensive research and development plan, along with an assembly and testing strategy for the Sensor Module. Readout Units testing is nearly complete, with large-scale production set to commence soon. Peking University, along with other institutions, has played an important role in this work. Our contributions mainly encompass the optimization of the sensor module coupling tool and the implementation of the sensor module QA/QC system through production, construction, and testing. Additionally, we participated in specific test beam projects, collaboratively determining specifications for SiPM and LYSO. In large-scale production, our responsibilities will extend to assembling a quarter of the modules while also undertaking other associated tasks.
超周边重离子碰撞物理实验研究进展
Within proton-lead collisions collected by the LHCb detector at nucleon-nucleon center-of-mass energy of 5 and 8.16 TeV, a rich set of open charm hadrons is observed with abundant statistics. Thanks to the LHCb forward acceptance that is complementary to general purpose detectors and excellent performance in particle reconstruction and identification, these charm states are studied down to zero $p_\mathrm{T}$ with overwhelming precision in heavy ion data. Presented in this talk is the measurements of production of charm mesons and baryons reconstructed in exclusive hadronic final states. The results on nuclear modification factors will give stringent test on the nuclear parton distribution function and parton saturation models. The hadronization mechanism of charm quarks are also studied. The production ratio of stranged $\Xi_c^+$ and $D_s^+$ over $D^+$ or $D^0$ will be presented, in order to search for possible strangeness enhancement in small-system collisions.
$~~~~$PHENIX experiment group points out that in the measurements of the $\pi^0$ nuclear modification factor $R_{dAu}^{\pi^0}$, $\langle N_{\rm coll} \rangle$ can be biased by the event-selection [1], which can be effectively reduced by using the direct $\gamma$ yield at large $p_{\rm T}$ to determine the $\langle N_{\rm coll}^{\gamma} \rangle = {\rm Y}_{dAu}^{\gamma^{\rm dir}}/{\rm Y}_{pp}^{\gamma^{\rm dir}}$ [2]. Utilizing the $\langle N_{\rm coll}^{\gamma} \rangle$ provided by PHENIX, the $\pi^0$ suppression is studied within a next-to-leading-order perturbative QCD parton model [3] incorporating the medium-modified parton fragmentation functions [4]. This study is under the assumption that the quark-gluon plasma (QGP) is produced, and its evolution can be described by hydrodynamics in $d$-$Au$ collisions at $\sqrt{s_{\rm NN}}$=200 GeV. The initial conditions and space-time evolution of the matter created in $d$-$Au$ collisions are provided by the superSONIC hydrodynamic model simulations [5,6] and parton energy loss in such a small medium is described by the high-twist (HT) approach [7]. The jet transport coefficient $\hat{q}/T^3(T)$ in this HT approach is extracted with the information field (IF)-Bayesian inference approach from all existing experimental data on single-inclusive hadron, dihadron, and $\gamma$-hadron spectra in heavy-ion collisions at RHIC and the LHC energies [8,9]. When only including the cold nuclear matter effect, the $\langle R_{dAu}^{\pi^0} \rangle$ averaged over $7.5 References
[1] J. Adam et al. [ALICE], Phys. Rev. C 91 (2015) no.6, 064905
[2] N. J. Abdulameer et al. [PHENIX], [arXiv:2303.12899 [nucl-ex]].
[3] J. F. Owens, Rev. Mod. Phys. 59 (1987), 465
[4] X. N. Wang, Phys. Rev. C 70 (2004), 031901
[5] P. Romatschke, Eur. Phys. J. C 75 (2015) no.7, 305
[6] R. D. Weller and P. Romatschke, Phys. Lett. B 774 (2017), 351-356
[7] X. f. Guo and X. N. Wang, Phys. Rev. Lett. 85 (2000), 3591-3594
[8] M. Xie, W. Ke, H. Zhang and X. N. Wang, Phys. Rev. C 108 (2023) no.1, L011901
[9] M. Xie, W. Ke, H. Zhang and X. N. Wang, [arXiv:2208.14419 [hep-ph]].
The recent observation of jet-associated deuteron production in pp collisions at √s = 13 TeV by the ALICE Collaboration opens a new window to study the production mechanism of light nuclei as well as the phase-space structure of jets produced in high-energy nuclear collisions. Here, we investigate jet effects on deuteron production in both pp and p-Pb collisions at the LHC energies, using the nucleon coalescence model for light nuclei production with the nucleon phase-space information obtained from A Multi-Phase Transport (AMPT) Model. In the low transverse momentum (pT ) region (pT /A < 1.5 GeV/c), covered by current measurements, the in-jet deuteron coalescence parameter B2 is found to be enhanced by factors of about 10 in pp collisions and 25 in p−Pb collisions, which are consistent with the recent ALICE measurements. In the higher pT region (pT /A > 2GeV/c), we find that both the yield ratio of deuteron to proton (d/p) and B2 are significantly larger in the Toward region than in the Transverse region, which is in line with the sharper two-nucleon angular distribution inside the jet cone, reflecting a genuine effect of jets.
We demonstrate the recently proposed nucleon energy-energy correlator (NEEC) fEEC (x, θ) can unveil the gluon saturation in the small-x regime in eA collisions. The novelty of this probe is that it is fully inclusive just like the deep-inelastic scattering (DIS), with no requirements of jets or hadrons but still provides an evident portal to the small-x dynamics through the shape of the θ-distribution. We find that the saturation prediction is significantly diferent from the expectation of the collinear factorization.
Nucleon spin structures and opportunities at EicC
The neutron skin thickness of the benchmark nuclei 208^Pb is crucial for our understanding of the equation of state of nuclear matter. Several observables in relativistic heavy ion collisions are found to be sensitive to the neutron skin, and the uncertainties from the bulk evolution can be canceled out by the collision of its isobaric partner. In this talk, we discuss the effect of the neutron skin on the ratio observables in semi-isobaric collisions, i.e., 208^Pb + 208^Pb collisions and 197^Au + 197^Au collisions. Our results indicate that the 208^Pb and 197^Au have similar magnitude of neutron skin thickness, as the two isobaric collision systems follow the same scaling behavior. Our results can shed light on the determinations of neutron skin and nuclear symmetry energy in relativistic heavy ion collisions.
In this talk I will review our recent efforts to understand the polarized Transverse-Momentum-Dependent fragmentaion functions (TMD FFs) . Recent BELLE results on $\Lambda/\bar\Lambda$ polarization in $e^+e^-$-annihilations stimulate a series of progress from several groups to understand the polarized TMD FF $D_{1T}^\perp$. Based on the fundamental isospin symmetry of QCD, we propose a new parametrization and apply it into $e^+e^-$-annihilation, semi-inclusive DIS and also hadron/nucleus collisions. The isospin symmetry and further flavor structures of $D_{1T}^\perp $ is thoroughly investigated, and several predictions for observables in current and future facilities are presented. We further study the weak decay contributions to the parity-violating TMD FFs, which cause several non-negligible effects.
We report our recent progress on the study of semi-inclusive deep inelastic scattring in the target fragmentation region with a polarized lepton beam and polarized nucleon target. In this region, the nonperturbative effects are factorized into fracture functions. We derive the results of structure functions up to twist-3 at the tree level of pQCD, and up to one loop level at twist-2. At the tree level, there are four structure functions at twist-2 and eight structure functions at twist-3. At one loop and twist-2, another six structure functions become nonzero in which four are generated uniquely by the gluon fracture functions. By combining the results, all eighteen structure functions for the process are predicted. Azimuthal and spin asymmetries are discussed in connection with relevant experiments.
References:
[1] K.B. Chen, J.P. Ma and X.B. Tong, JHEP 05(2024)298.
[2] K.B. Chen, J.P. Ma and X.B. Tong, Phys. Rev. D 108 (2023) 094015.
The shape phase transition for certain isotope or isotone chains, associated with the quantum phase transition of finite nuclei, is an intriguing phenomenon in nuclear physics. A notable case is the Xe isotope chain, where the structure transits from a $\gamma$-soft rotor to a spherical vibrator, with the second-order shape phase transition occurring in the vicinity of $^{128−130}$Xe. In this work, we focus on investigating the $\gamma$-soft deformation of $^{129}$Xe associated with the second-order shape phase transition by constructing novel correlators for ultra-relativistic $^{129}$Xe+$^{129}$Xe collisions. In particular, our iEBE-VISHNU model calculations show that the $v_{2}^2-[p_T]$ correlation $\rho_2$ and the mean transverse momentum fluctuation $\Gamma_{p_T}$, which were previously interpreted as the evidence for the rigid triaxial deformation of $^{129}$Xe, can also be well explained by the $\gamma$-soft deformation of $^{129}$Xe. We also propose two novel correlators $\rho_{4,2}$ and $\rho_{2,4}$, which carry non-trivial higher-order correlations and show unique capabilities to distinguish between the $\gamma$-soft and the rigid triaxial deformation of $^{129}$Xe in $^{129}$Xe+$^{129}$Xe collisions at the LHC. The present study also provides a novel way to explore the second-order shape phase transition of finite nuclei with ultra-relativistic heavy ion collisions.
With an electron-positron collider operating at center-of-mass-energy 2∼7 GeV and a peak luminosity above 0.5 × 1035 cm−2 s−1, the STCF physics program will provide an unique platform for in-depth studies of hadron structure and non-perturbative strong interaction, as well as probing physics beyond the Standard Model at the τ-Charm sector suceeding the present Being Electron-Positron Collider II (BEPCII). A performant, extendable and maintenable offline event processing software to reconstruct and identfiy particles and events is very crucial to the design and construction of the detectors, and to eventually fulfill the physics targets and to further maximize the physics potential at the STCF.
In this talk, I will give an overview of the STCF offline event processing software, focusing on the event reconstruction algorithms and physics analysis tools implemented for STCF and their performance. Innovative algorithms such as machine learning techniques which are exploited to maximize the overall performance will be highlighted.
LHCb Upgrade II is a proposed detector upgrade for the fourth long-term shutdown of the LHC, which will operate at instantaneous luminosities up to $1.5 \times 10^{34} cm^{-2} s^{-1}$ and integral luminosities totaling about 300 $fb^{-1}$. The upgrade will fully collect and utilize the flavor physics opportunities offered by the HL-LHC and to explore a wide range of observable physics with unprecedented precision. The required substantial modifications of the current LHCb electromagnetic calorimeter (ECAL) due to high radiation doses in the central region and increased particle densities are referred to as PicoCal.
Currently, a number of scintillating sampling ECAL technologies are under investigation as part of an ongoing research and development effort. These technologies include the Spaghetti Calorimeter (SpaCal) utilizing garnet scintillating crystals with tungsten absorbers, SpaCal utilizing scintillating plastic fibers with tungsten or lead absorbers, and the Shashlik configuration featuring polystyrene tiles, lead absorbers, and fast wavelength-shifting fibers. Additionally, corresponding simulation and reconstruction software packages have been developed in conjunction with these studies. Timing capabilities with tens of picoseconds precision for neutral electromagnetic particles and increased granularity with denser absorber in the central region are needed for pile-up mitigation. A front-to-back longitudinal layered readout structure has also been introduced into the prototype with a view to improving the splitting performance of overlapping clusters. For both the SpaCal and Shashlik modules, we obtained a time resolution better than 20 ps at high energy. And the sampling term for energy resolution is about 10/sqrt(E) meets the requirement. Several typical ands benchmark analyses have been carried out, to demonstrate the performance of the PicoCal.
The talk will highlight the novel software developments for the PicoCal and the related important physics prospects.
A particle flow oriented high granularity Analog Hadronic Calorimeter (AHCAL) has been designed for the Circular Electron Positron Collider (CEPC). An AHCAL prototype consisting of 40 longitudinal layers with a transverse granularity of , using scintillator tiles as active material and stainless steel as absorber, has been constructed and tested at the CERN SPS H2 beam line. About 30 millions of test-beam data corresponding to muon, electron, and charged pion events are collected.
We developed a pattern recognition algorithm based on fractal dimension and average hit energy. The FD serves as a characteristic property of a fractal, providing a quantitative descriptor of the complexity of the shower shape, and is designed for high granularity calorimeters with good separation power. Using this algorithm, we quantified the PID efficiency with Monte Carlo samples. The noise, MIP, EM, hadronic components and other interesting events in the data are observed and separated by artificial cuts. The fractions of these components as a function of beam energy are estimated. This algorithm performed a good purity analysis of the test beam data.
The precise measurements of the Higgs, W and Z boson properties at future electron-positron collider will provide critical tests of the Standard Model (SM) and are essential in the exploration of new physics beyond the SM (BSM). To distinguish the hadronic decays of W and Z bosons, a 3-4% jet energy resolution for two-jet systems is required. The particle flow approach, which aims to measure individual particles in jets using imaging calorimeter system, is a very promising method to achieve the unprecedented jet energy resolution.
A novel electromagnetic calorimeter (ECAL) with orthogonally arranged crystal bars has been proposed. The crystal bar design is expected to provide optimal intrinsic energy resolution and three-dimensional shower information for the particle flow algorithm (PFA). Additionally, the long bar design will significantly reduce the cost of electronics. However, the crystal bar ECAL also presents challenges, such as the potential ambiguity problem for multiple particles due to the perpendicular arrangement of crystal bars in adjacent layers and increased shower overlap from different particles caused by the larger $R_M$ and $X_0/\lambda_I$ for crystals.
This report presents recent progress on the new PFA dedicated to the crystal bar ECAL. The ambiguity problem has been addressed through the implementation of multiple optimized pattern recognition approaches, while the issue of shower overlap has been mitigated by an energy splitting module. The development of the PFA takes into account various aspects including electronics, heat dissipation, mechanical support, and digitization processes of ECAL. The algorithm’s performance, including a boson mass resolution of approximately 3.9%, will be demonstrated. These results underscore the potential of the proposed ECAL design and the PFA in enhancing detector capabilities and reconstruction methodologies for future electron-positron collider experiments.
液体闪烁体是中微子实验中最常用的探测介质,精确重建液闪中事例的能量和位置对于粒子鉴别和提高信噪比等至关重要。我们引入对暗噪声的考虑,建立了点源响应与暗噪声的混合模型,未来也可以推广到闪烁光与切伦科夫光的混合、多个点源的混合模型。基于该混合模型,利用马尔可夫链蒙特卡罗方法(MCMC)将光电子和顶点位置及时刻的后验分布采样进行链式对接,将波形分析和事例重建联合起来。这种联合重建方法能够更精确地估计光电子数和位置,从而显著提高能量分辨率。我们的方法已经在锦屏中微子实验(JNE)的事例重建上取得了初步结果。通过采用这种重建方法,可以推动我们对中微子物理的理解,并提高未来实验的准确性。
在高亮度对撞环境下,未来的粒子物理实验将面临前所未有的空间兼时间上的高堆积率和高本底率。例如,在 HL-LHC 上,质子质子对撞的平均堆积水平(pile-up)将达到 200,是 LHC 上的三倍多。通过联合的高精度位置和时间测量信息对堆积的物理信号和本底信号进行精确“拆分”,是未来高亮度对撞机实验的谱仪系统的关键技术之一。例如,在 HL-LHC 阶段,ATLAS 将在径迹探测器端盖外侧安装基于高时间分辨的时间探测器(HGTD),利用径迹的时间信息来去掉仅利用空间信息无法区分的堆积本底。在桶部部分,人们也在探讨未来将内层硅像素探测器替换成含时间测量的4D硅像素探测器的可能性和物理潜力。
在探测器研发阶段,用于粒子径迹探测的束流望远镜是在真实环境下验证探测器原型的分辨和效率等性能的重要工具。为了避免多径迹引起的击中匹配错误,传统的束流望远镜的触发事例大多数为单径迹事例,以确保束流望远镜径迹与被测试探测器模块击中能精确匹配,但这大大影响了束流实验取数的速度。基于国际上新兴的通用径迹重建软件ACTS, 我们研究了将含有时间信息的硅像素探测器应用于束流望远镜系统以提高可处理的径迹数/事例和最终的取数速度的可能性。同时,束流望远镜系统本身作为一个径迹探测器,其在含时间测量信息下的效率、分辨等径迹重建性能的改善,也为未来对撞机上的4D径迹重建研究提供了重要参考。
本报告将简单回顾国际上常用的粒子束流望远镜系统,并介绍基于ACTS的束流望远镜系统的全模拟和径迹重建,最后着重展示在含有不同分辨的时间测量信息情况下的4D束流望远镜的径迹重建性能的改善和在多径迹情况下的稳健性。
高能宇宙辐射探测设施(HERD)是计划部署在中国空间站上的科学装置,它的主要科学目标包括间接探测暗物质、精确测量宇宙线能谱以及高能伽马射线巡天观测。HERD离线软件(HERDOS)是整个实验的重要组成部分,主要负责离线数据处理,包括蒙特卡洛模拟、刻度、重建和物理分析等。HERDOS以我国自主研发的轻量级的SNiPER软件框架为基础,同时利用了一些高能物理中最先进的第三方软件,例如DD4hep、podio、TBB等。
本文将概述HERDOS的设计和实现细节,具体将讨论以下内容:
1.基于podio设计的事例数据模型(EDM),以及通过整合SNiPER和podio实现的数据管理系统(DMS)。
2.基于SNiPER和TBB实现的并行化的数据管理系统,包括基于podio开发的GlobalStore,以实现并发数据访问和数据输入输出。
3.基于MT-SNiPER开发的并行化的探测器模拟系统,包括事例级别和径迹级别的并行模拟。
4.基于DD4hep开发的几何管理系统,可以提供一致的的探测器描述以及获取探测器描述信息的接口。
目前,HERDOS已经在探测器设计等方面实现有效运行,同时在物理研究上也有着巨大潜力。
Modern particle physics experiments usually rely on highly complex and large-scale spectrometer devices. In high energy physics experiments, visualization helps detector design, data quality monitoring, offline data processing, and has great potential for improving physics analysis. In addition to the traditional physics data analysis based on statistical methods, visualization provides unique intuitive advantages in searching for rare signal events and reducing background noises. By applying the event display tool to several physics analyses in the BESIII experiment, we demonstrate that visualization can benefit potential physics discovery and improve the signal significance. With the development of modern visualization techniques, it is expected to play a more important role in future data processing and physics analysis of particle physics experiments.
The data processing and analyzing is one of the main challenges at HEP experiments, normally one physics result can take more than 3 years to be conducted. To accelerate the physics analysis and drive new physics discovery, the rapidly developing Large Language Model (LLM) is the most promising approach, it have demonstrated astonishing capabilities in recognition and generation of text while most parts of physics analysis can be benefitted. In this talk we will discuss the construction of a dedicated intelligent agent, an AI assistant at BESIII based on LLM, the potential usage to boost hadron spectroscopy study, and the future plan towards a AI scientist.
原初电离计数方法是具有突破性的下一代粒子物理实验探测器方法,它通过测量带电粒子在气体径迹探测器中的原初电离数目(dN/dx),实现带电强子的鉴别。与传统电离能损(dE/dx)方法相比规避了测量中的多项涨落,理论分辨率有潜力比dE/dx好两倍,是下一代先进探测器技术的有力候选。对于漂移室的 dN/dx 方法,原初电离簇团的重建存在着巨大的挑战。其一,原初电离簇团常常在电流波形上形成高堆积、高噪声的信号;另外,次级电离会对初级电离的测量造成严重污染。传统算法难以对上述问题进行有效地解决。
深度学习算法近些年在工业界和高能物理界都取得了重大突破,其性能在很多领域远超传统算法。经典的深度学习算法利用大量有标注数据(仿真数据),利用监督学习的方法,可以学习到数据中的复杂规律。但对于真实实验数据,通常难以获得高质量的标注,经典的监督学习则面临困难。领域自适应是迁移学习的一种,它通过建立仿真数据与真实数据之间的关联,对信息进行迁移,从而将大统计量仿真数据的信息应用到数据的训练中。
本研究对于仿真数据样本,开发了基于长短记忆网络(LSTM)和动态图神经网络(DGCNN)的监督模型。在K介子与π介子的粒子鉴别区分能力方面,相比传统算法取得了 10% 的显著改进。该结果相当于在相同的性能下,将探测器的尺寸减少 20%,从而节省了巨大的成本。对于在CERN收集的束流实验数据样本,由于缺少标注、以及和仿真数据存在差异,我们开发了基于最优传输的半监督领域自适应模型。该模型的性能优于传统方法,且与监督模型接近。
已经有两篇相关论文投递给了期刊:2402.16270和2402.16493。其中,关于迁移学习的论文已在《Computer Physics Communications》上发表(CPC 300, 109208 (2004))。
Generative networks, such as ChatGPT, have recently gained significant popularity. There are also many applications of generative networks in the field of particle physics. One area of active research focuses on the development of fast simulation methods for calorimeters. This research is primarily driven by the experiments conducted at the LHC. In the upcoming HL-LHC phase, a substantial volume of experimental data will be collected. For MC simulation, it is necessary to generate samples with statistics that exceed those of the experimental data, which consumes a significant amount of computational resources. Without conducting relevant research and development, there is a risk of facing a shortage of computational resources.
In traditional Geant4 simulation methods, the simulation of calorimeters is the most time-consuming part. By employing fast simulation methods based on machine learning, it can greatly accelerate this process, thereby addressing the issue of limited computational resources. This presentation will introduce the use of machine learning for fast calorimeter simulation and explore its applications in different experiments.
The rapid development of Deep Learning and Quantum Computing has benefited or potentially will benefit high-energy physics experiments. To enhance the scientific discovery power of high-energy collider experiments, we propose and realize the concept of jet-origin identification, which categorizes jets into five quark species (b, c, s, u, d), their corresponding antiquarks, and the gluon. We uniquely solve jet clustering using the Quantum Approximate Optimization Algorithm (QAOA). For small-scale jet clustering problems, the QAOA has achieved performance similar to the classical jet clustering algorithm, ee_kt.
径迹重建是对撞机实验离线数据处理中最重要和最具挑战性的任务之一。针对漂移室的径迹重建先前已有了大量成功的研究工作,例如用于径迹寻找的模式识别(PAT)、径迹段寻找(TSF)以及霍夫变换(Hough transform),用于径迹拟合的最小二乘法、龙格库塔拟合和卡尔曼滤波等。然而,传统的径迹重建算法在处理低动量径迹、来自次级顶点的径迹和高噪声水平的情况下仍存在一定的局限性 。为了克服这些挑战,本研究提出了一种基于图神经网络的新型漂移室径迹重建算法,旨在提高寻迹性能。首先,利用大量的MC样本建立了表示漂移单元之间相邻关系的模式库,并设计了相应的构图方法,然后训练了一个边分类的图神经网络来区分径迹上的击中和噪声击中。接下来,通过DBSCAN联合RANSAC算法在参数空间对筛选出的击中进行聚类,聚类出的候选径迹经过GENFIT2拟合,最终得到径迹参数。将该方法用于处理BESIII MC样本和STCF MC样本,均取得了良好的初步结果,并展现出了在其他含漂移室实验(如CEPC和BELLE II)中的潜力。
北京谱仪(BESIII)实验是目前国际上唯一运行在𝜏−粲能区的大型粒子物理实验装置,为𝜏−粲能区的物理课题提供了重要的研究平台。𝜏−粲能区的物理过程,末态中含有较多的强子成分,因此粒子鉴别非常重要。
目前BESIII实验通过联合dE/dx和飞行时间实现粒子鉴别,由于没有切伦科夫探测器,因此在高动量区域的粒子鉴别效率较低,不能充分满足物理需求。所以,如何最大程度获取粒子鉴别能力,是一个关键科学问题。
实际上BESIII四个子探测器都具有一定程度的粒子鉴别能力,但由于不同探测器信息之间的关联十分复杂,传统方法处理起来极其困难,不能获得最佳的粒子鉴别性能。而机器学习方法在解决这种复杂关联问题时具有强大的优势。
因此,我在BESIII实验上利用机器学习方法开展了粒子鉴别的研究。
我选用深度神经网络(DNN)方法,通过参数调试和模型训练,得到适用于BESIII实验𝜋,𝐾,𝑝强子鉴别的机器学习模型。目前模型已经实现了在BESIII软件算法中的部署。与传统方法相比,基于深度神经网络的粒子鉴别算法在高动量区域的粒子鉴别效率得到显著提高,而时间消耗基本没有增加。同时,通过分开训练真实数据和模拟数据,系统误差也有较大的改善。更高效的粒子鉴别效率和更小的系统误差,将有效提升信号显著性,改善物理精度。
超级陶粲装置(STCF)是中国正在筹划的新一代正负电子对撞机,是研究宇宙中正反物质不对称、探索强子内部结构、寻找奇特态强子和新物理的独特平台。粒子鉴别(PID)作为STCF实验中各种物理研究中最基本的工具之一,对于实现STCF的各种物理目标至关重要。在最近几十年中,机器学习(ML)逐步成为高能物理实验中粒子鉴别的强大替代方法。ML算法,例如神经网络和提升决策树,在处理复杂和多维数据方面表现出卓越性能,所以它们非常适合整合来自多个子探测器系统的粒子鉴别信息。在这项工作中,我们提出了一种基于ML技术的强大PID软件,包括一个全局PID算法用于合并所有子探测器信息实现带电粒子鉴别,以及一个基于量能器响应区分中性粒子的深度CNN算法。初步结果显示基于ML的PID算法取得了出色的粒子鉴别性能,极大地提升了STCF的物理潜力。
超级陶粲装置(STCF)是中国未来的正负电子对撞机,其质心能量范围为2-7 Gev,峰值亮度可达$0.5\times 10^{35} \mathrm{~cm}^{-2} \mathrm{~s}^{-1} $。在STCF中,许多物理过程的末态粒子动量较高,这便对高动量粒子的鉴别提出了更高的要求。比如在动量达2Gev/c时,需要对$\pi$的鉴别效率超过97%,同时$K$的误鉴别率低于2%。因此,STCF设计了两个切伦科夫探测器(RICH和DTOF)来提高粒子鉴别(PID)性能。
针对STCF中的$\pi$/$K$鉴别问题,我们在DTOF探测器上开发了一个基于卷积神经网络(CNN)的PID算法,该算法主要利用了切伦科夫光子在多阳极微通道板光电倍增管处的击中通道和到达时间。目前,CNN算法在绝大部分动量和角度范围内,对$\pi$的鉴别效率达到了99%,充分满足了STCF的物理需求。此外,基于经典CNN,我们还进行了量子卷积神经网络(QCNN)的概念验证研究,以探索其可行性和潜在的量子优势。初步结果表明QCNN在相同数据集上具有优于经典CNN的潜力。
环形正负电子对撞机(Circular Electron Positron Collider, CEPC)实验,主要用于精确测量希格斯玻色子的性质,并寻找超越标准模型的新物理。CEPC的顶点探测器(VTX detector)位于探测器最内层,在确定碰撞事件的顶点方面起着主导作用, 对碰撞事件重建与分辨至关重要。顶点探测器还负责为后续重建算法提供种子,以在外部探测器中寻找径迹。TRACCC是ACTS的研发线之一,旨在开发出能在异构设备上加速运行的、通用的径迹重建算法。
本报告将介绍:基于TRACCC开发CEPC顶点探测器种子寻找算法,并将其集成到CEPC软件(CEPC software, CEPCSW)环境中。CEPCSW采用Gaudi作为底层框架,使用DD4hep作为探测器描述工具、EDM4hep作为事件数据模型。CEPC顶点探测器有三层,每层的两侧都安装有硅像素传感器。为适应这种特定的探测器结构,TRACCC中的默认种子寻找算法(使用三个空间点组成一个种子)已被扩展为使用六个空间点组成种子的算法。此外,报告还介绍了一种在种子寻找算法中优化内存使用的方法,通过使EDM4hep和VecMem共享内存,避免了数据复制带来的额外开销。最后,报告将展示上述工作的物理性能和计算性能测试结果,并进行评估和分析。
It is usually believed that physics in off-equilibrium state can be equivalently studied using equilibrium state with suitable metric perturbation. We point out it is not the case for spin polarization phenomena: the exisiting chiral kinetic theory in curved space fails to recover all the couplings between spin and hydrodynamic gradients [1]. We present a new form of chiral kinetic theory in curved space, in which the equivalence is established [2]. The equivalence allows us to formulate spin polarization in hydrodynamic medium as a scattering problem, which is then studied using in-medium form factors [3,4]. We find radiative corrections to all couplings between spin and hydrodynamic gradients. Implications for local spin polarization of Lambda hyperon will be discussed.
[1] Y.-C. Liu, L.-L. Gao, K. Mameda and X.-G. Huang, Phys.Rev.D 99 (2019) 8, 085014
[2] J. Tian and S. Lin, to appear
[3] S. Lin and J. Tian, Acta Phys.Sin. 72 (2023) 7, 071201
[4] S. Lin and J. Tian, Eur.Phys.J.Plus 139 (2024) 2, 109
非对心相对论重离子碰撞中产生的系统具有极强的涡旋结构,垂直于反应平面方向的轨道角动量可导致末态超子的整体极化(global polarization),而沿着束流方向的集体流涡旋效应则导致超子的局域极化现象(local polarization)。超子的自旋极化效应作为探索强相互作用物质流体性质的新方法,目前已取得了丰富的实验测量和理论研究结果,同时也存在一些亟需解决的问题,如末态磁场的影响、整体极化的碰撞系统尺寸依赖性、低能区的局域极化性质等。
本次报告中,我们将介绍RHIC-STAR实验上BES-II能区金核-金核碰撞以及200 GeV 同质异位素碰撞中$\Lambda$($\bar\Lambda$)超子的整体极化和局域极化测量结果。这些测量结果将为相对论重离子碰撞中磁场的影响、涡旋场精细结构及自旋极化物理机制的研究提供更加丰富的数据支撑,对于解决理论模型中的磁场、涡旋场、剪切黏滞效应等物理问题提供关键实验证据。
We derive the chiral kinetic equation in non-Abelian gauge field with consistent semiclassical expansion. Within new expansion scheme, we disentangle the Wigner equations up the second order and find that Wigner equations do not lead to constraint equations. We integrate the covariant chiral kinetic equations in eight-dimensional phase space and obtain the chiral kinetic equations in seven-dimensional phase space.
STAR合作组在《自然》杂志上发表了他们对高能重离子碰撞中$\Lambda$超子整体极化和$\phi$,$K^{*0}$矢量介子整体自旋排列的实验结果[1,2],不仅证实了夸克物质整体极化这一新现象[3,4],使自旋极化的研究成为高能核物理前沿新方向,而且表明在相对论性重离子碰撞中,夸克和反夸克在反应平面法线方向上可能存在很强的自旋关联,从而使夸克自旋关联的研究成为当前该方向新的增长点。在文献[5]中,我们提出了一种系统性的方法来描述夸克物质中的这种关联,并将其分类为局域和长程夸克自旋关联。我们的研究表明有效的夸克自旋关联包括直接源于动力学过程的真正自旋关联,以及考虑其它自由度平均引起的诱导关联。我们还展示了如何通过测量矢量介子的自旋密度矩阵以及超子-超子和超子-反超子的自旋关联来研究这种关联,并阐明了这些可观测量与夸克和反夸克自旋关联之间的关系。本报告的目标是系统介绍[5]中关于夸克自旋关联的研究,并对未来发展进行讨论。
参考文献
[1] L. Adamczyk et al. [STAR Collaboration], “Global Λ hyperon polarization in nuclear colli-
sions: evidence for the most vortical fluid,” Nature 548, 62 (2017). doi:10.1038/nature23004.
[arXiv:1701.06657 [nucl-ex]].
[2] M. S. Abdallah et al. [STAR], Nature 614, no.7947, 244-248 (2023) doi:10.1038/s41586-022-
05557-5 [arXiv:2204.02302 [hep-ph]].
[3] Z. T. Liang and X. N. Wang, “Globally polarized quark-gluon plasma in non-central A+A
collisions,” Phys. Rev. Lett. 94, 102301 (2005) [erratum: Phys. Rev. Lett. 96, 039901 (2006)]
doi:10.1103/PhysRevLett.94.102301 [arXiv:nucl-th/0410079 [nucl-th]].
[4] Z. T. Liang and X. N. Wang, Phys. Lett. B 629, 20-26 (2005)
doi:10.1016/j.physletb.2005.09.060 [arXiv:nucl-th/0411101 [nucl-th]].
[5] J. P. Lv, Z. H. Yu, Z. T. Liang, Q. Wang and X. N. Wang, Phys. Rev. D 109,114003(2024)
doi:10.1103/PhysRevD.109.114003 [arXiv:2402.13721 [hep-ph]].
We present a new derivation of relativistic second-order spin hydrodynamics for quantum systems using Zubarev’s non-equilibrium statistical-operator formalism. This is achieved by a systematic expansion of the energy-momentum tensor, the spin tensor and the charge current to second order in deviations from equilibrium. As a concrete example, we obtain the relaxation equations for the shear-stress tensor, the bulk-viscous pressure, the charge-diffusion currents and the dissipative currents appearing in the spin tensor required to close the set of equations of motion for relativistic second-order spin hydrodynamics. We also identify new transport coefficients which describe the relaxation of dissipative processes to second-order and express them in terms of equilibrium correlation functions, thus establishing new Kubo-type formulas for second-order transport coefficients.
Lattice QCD study of heavy quark diffusion
Exploring the location of the critical end point (CEP) in the Quantum Chromodynamics (QCD) phase diagram is an important scientific problem that has remained unsolved for decades. Recent studies suggest that the CEP may exist within the QCD matter produced in the beam energy scan project of heavy ion collisions at $\sqrt{s_{NN}} = 3-7.7$ GeV. First-principle Lattice QCD calculations are hindered by the well-known sign problem at such high baryon chemical potential. We have developed a quasi-particle model for hot and dense QCD matter, where three artificial neural networks are constructed to represent the masses of quasi-particles as functions of temperature $T$ and baryon chemical potential $\mu_B$. This model is calibrated using data from lattice QCD and hadron resonance gas at zero $\mu_B$. The equations of state derived from our quasi-particle model are in good agreement with Lattice QCD results at small $\mu_B$, using Taylor expansion. Moreover, through susceptibility analysis, the quasi-particle model predicts that the CEP is approximately located at $(\mu_B, T) = (630, 116)$ MeV.
Understanding the properties of hypernuclei helps to constrain the interaction between hyperon and nucleon, which is known to play an essential role in determining the properties of neutron stars. Experimental measurements have suggested that the hypertriton ($^3_\Lambda \text{H}$), the lightest hypernucleus, exhibits a halo structure with a deuteron core encircled by a $\Lambda$ hyperon at a distance of about 10 fm. This large $\Lambda-d$ distance in $^3_\Lambda \text{H}$ wave function is found to cause a suppressed $^3_\Lambda \text{H}$ yield and a softening of its transverse momentum ($p_T$) spectrum in relativistic heavy-ion collisions. Within the coalescence model based on nucleons and $\Lambda$ hyperons from a microscopic hybrid hydro model with a hadronic afterburner for nuclear cluster production in Pb-Pb collisions at $\sqrt{s_{NN}}$= 5.02 TeV, we show how this softening of the hypertriton $p_T$ spectrum appears and leads to a significantly smaller mean $p_T$ for $^3_\Lambda \text{H}$ than for helium-3 ($^3$He). The latter is opposite to the predictions from the blast-wave model which assumes that $^3_\Lambda \text{H}$ and $^3$He are thermally produced at the kinetic freeze-out of heavy ion collisions. The discovered quantum mechanical softening of the (anti-)hypertriton spectrum can be experimentally tested in relativistic heavy-ion collisions at different collision energies and centralities and used to obtain valuable insights to the mechanisms for light (hyper-)nuclei production in these collisions.
The yield ratio of light nuclei produced in heavy-ion collisions, defined as $N_t \times N_p/N_d^2$, is a promising probe for the critical endpoint in the QCD phase diagram. In the coalescence model of light nucleus production, the triton yield $N_t$ and deuteron yield $N_d$ are sensitive to the relative distance $\Delta r$ between each pair of nucleons in the Wigner function. However, the effect of the two-nucleon distribution $\rho(\Delta r)$ in the colliding nucleus on the yield ratio has not been extensively investigated. In this work, we developed a method to sample nucleons in the $^{197}Au$ nucleus satisfying both the single-particle distribution $f(r)$ and the two-nucleon distribution function $\rho(\Delta r)$. Using these sampled $^{197}Au$ nucleus, we calculated the proton, deuteron and triton yields in Au+Au collisions at $\sqrt{s_{NN}}=3 GeV$ using the SMASH transport model simulations. The calculated yield ratios, differential $p_T$ distributions and mean transverse momentum $\left \langle p_T \right \rangle$ different centrality regions and rapidity windows agree well with experimental measurements from the STAR experiment. Our results suggest that initial nucleon-nucleon correlations have a visible effect on light particle production, indicating that the yield ratio of light nuclei in heavy ion collisions might provide a good probe for nucleon-nucleon correlation in the nuclear structure.
Despite extensive measurements on the production yields of light nuclei in heavy-ion collisions, a consensus on their formation mechanism remains elusive. In contrast to normal nuclei, hypernuclei carries strangeness and can offer an additional dimension for such studies. In particular, the hypertriton ${}^{3}_{\Lambda}{\rm H}$, a bound state consisting of a proton, neutron and $\Lambda$ hyperon, is the lightest known hypernucleus with a very small binding energy of $\sim 130$ keV. Currently, published measurements of the ${}^{3}_{\Lambda}{\rm H}$ yield are scarce and are limited to low ($\sqrt{s_{_\mathrm{NN}}}<5$ GeV) or high collision energies ($\sqrt{s_{_\mathrm{NN}}}\geq 200$ GeV). Precise measurements on the energy dependence of ${}^{3}_{\Lambda}{\rm H}$ production will give invaluable information on hypernuclei production mechanisms due to its unique intrinsic properties.
In this presentation, we will present comprehensive measurements of the collision energy dependence of ${}^{3}_{\Lambda}{\rm H}$ transverse momentum $p_{\rm T}$ and $p_{\rm T}$ -integrated yield at mid-rapidity in Au+Au collisions at ten collision energies between $\sqrt{s_{_\mathrm{NN}}}=$ 3 and 27 GeV. It is found that thermal model calculations overestimated the ${}^{3}_{\Lambda}{\rm H}$ yield and the ${}^{3}_{\Lambda}{\rm H}/\Lambda$ ratio by a factor of $\sim 2$ in the reported energy region, while coalescence calculations are closer to data. We will also present the mean $p_{\rm T}$ of ${}^{3}_{\Lambda}{\rm H}$ as a function of collision energy. The mean $p_{\rm T}$ of ${}^{3}_{\Lambda}{\rm H}$ is observed to be lower than the Blast-Wave expectation using the same freeze-out parameters from light hadrons. These observations suggest that similar to light nuclei, hypertritons are formed at a later stage than light hadrons possibly through nucleon/hyperon coalescence during these collisions.
为了充分利用高亮度大型强子对撞机为味物理带来的机遇,LHCb实验计划在2032年左右对整个探测器进行二期升级,以应对高事例堆积、高辐照剂量等极端运行环境带来的一系列挑战。在LHCb探测器二期升级中,电磁量能器PicoCal最靠近束流管区域计划采用基于高精度致密钨栅格和超快GAGG晶体的SPACAL技术,LHCb中国组正在主导相关技术的研发。本报告将重点介绍LHCb电磁量能器升级的整体设计,中国组在高性能闪烁晶体(GAGG晶体)的研制,高精度致密钨吸收体开发,原型机研制,以及相关的模拟、测试和束流实验等。
Following the demand for precise measurements of the Higgs, Z/W bosons and the top quark, future lepton colliders, e.g. the Circular Electron Positron Collider (CEPC), are required to meet stringent requirements on the calorimetry systems to achieve unprecedented jet energy resolutions. As part of CEPC’s “4th detector concept”, a novel high-granularity crystal electromagnetic calorimeter (ECAL) has been proposed, with an optimal EM resolution of $2-3\%/\sqrt{E(GeV)}$ and sufficiently low detection limit of photons. By utilising the Particle Flow Approach (PFA) with other optimised sub-detectors, this new ECAL design concept is expected to improve the Boson Mass Resolution (BMR) from 4% in the CEPC CDR to 3% level.
Significant R&D efforts have been undertaken in the design of this crystal ECAL. Geant4 full simulations have been carried out to assess the impact of light yield and time response of the crystal. Laboratory measurements with characterisations of crystal, silicon photo-multipliers (SiPMs) and readout electronics have been conducted, providing validation of the simulations and evidence on the hardware feasibility. Besides, a small-scale crystal module has been developed and tested under beam conditions for performance studies and system-level investigations.
This report introduces the design of the novel high-granularity crystal ECAL, outlines its physics potential, and presents the latest progress on hardware activities.
The Super Tau-Charm Facility (STCF) is the next generation high luminosity $e^{+}e^{-}$ collider focusing on the tau-charm physics. STCF will achieve a luminosity of over $0.5\times10^{35} cm^{-2}s^{-1}$ at 4 GeV, resulting in a high event rate and a high beam background for the detector system. The background count rate of over 1 MHz per module places new demands on the electromagnetic calorimeter (EMC): maintaining good energy and position resolution under severe pileup conditions. Meanwhile, the development of event timing and particle identification capability is also an important aspect of calorimeter R&D, where a time resolution of better than hundreds of picoseconds is expected.
The STCF EMC is based on a fast pure $CsI$ crystal and is read out by avalanche photodiodes (APD). By considering the effect of crystal and electronics response, as well as the pileup condition, a complete chain of simulation and reconstruction is implemented in the Offline Software of Super Tau-Charm Facility (OSCAR). The architecture and module geometry of EMC are designed by optimizing the physical performance under OSCAR. Based on the module design, a novel wavelength shifter (WLS)-enhanced prototype is fabricated, which features fast time response and good signal-to-noise ratio at a reasonable cost. The comprehensive test results on the prototype, especially on the radiation hardness of the prototype, the uniformity of the light collection and the cosmic ray-timing performance of the prototype, are also presented.
随着塑闪光纤工艺和具备单光子探测能力的硅光电倍增器(Silicon photomultipliers, SiPM)的发展,基于SiPM 阵列读出的塑料闪烁光纤探测器在设计制造上的成本和复杂度降低,可实现多种尺寸和形状的制备,甚至能够提供与传统硅微条探测器相当的高位置分辨率,因而在空间和地面的粒子物理实验中具有广泛的应用前景。该报告将从探测器模拟、器件测试、模块制备以及读出电子学等方面,介绍大尺寸、高位置分辨的塑料闪烁光纤探测器设计原理和研究进展。
低温高密核物质测量谱仪,即兰州重离子加速器冷却储存环外靶实验(CSR External target Experiment,简称CEE),将是我国第一台运行于GeV 能区的完全自主研制的大型核物理实验装置。CEE实验通过对重离子碰撞产物的近全空间测量,对低温高密相区的核物质状态的结构和性质开展深入研究。在CEE谱仪下游方向的束流线附近设计零度角量能器(Zero-Degree Calorimeter,简称ZDC),测量前角区带电粒子在探测器中的沉积能量和位置分布,用于重建碰撞事件平面和确定事件中心度。ZDC可实现500 MeV铀-铀碰撞的事件平面重建和事件中心度区分,物理模拟结果表明一阶事件平面分辨率可达90%,基于机器学习方法,在95%纯度条件下对中心碰撞和边缘碰撞的分类效率分别为41%和94%。ZDC采用“塑闪+光导+真空光电倍增管”的探测器设计方案,并采用“多通道电荷灵敏前放+波形数字化”的电子学读出方案,在电子学性能、宇宙线和束流(350 MeV的Kr束轰击铁靶)测试中运行稳定,各项性能达到了设计要求。本文将从CEE/ZDC探测器的设计、研制和物理性能等方面进行汇报。
Ref. https://arxiv.org/abs/2311.01780
The sensitivity of the dark photon search through invisible decay final states in low background experiments significantly relies on the neutron and muon veto efficiency, which depends on the amount of material used and the design of detector geometry. This paper presents an optimized design of a hadronic calorimeter (HCAL) used for the DarkSHINE experiment, which is studied using a GEANT4-based simulation framework. The geometry is optimized by comparing a traditional design with uniform absorbers to one that uses different thicknesses at different locations of the detector, which enhances the efficiency of vetoing low-energy neutrons at the sub-GeV level. The overall size and total amount of material used in HCAL are optimized to be lower due to the load and budget requirements, while the overall performance is studied to meet the physical objectives.
基于日本BEllE II探测器的升级,其用于探测$K_{L}$强子以及$\mu$子的KLM子探测器由RPC替换为塑料闪烁体,解决了RPC探测器长死时间在高亮度对撞实验中不适用的问题。目前BELLE II KLM探测器的方案为塑料闪烁体内嵌波长位移光纤与SiPM(硅光电倍增管)进行耦合,这样的结构具有高的探测效率,并能保证1.5 $ns$的时间分辨。这样的结构同样适用于CEPC中的缪子探测系统。为了进一步提高时间分辨,我们对TOF-like的塑料闪烁体探测系统进行了研究,采用了新的耦合方式并升级了电子学系统,对于长塑料闪烁体可达到70 $ps$以下的时间分辨。
The Circular Electron Positron Collider (CEPC) is a proposed future high-energy lepton collider aimed at advancing our understanding of fundamental physics by exploring Higgs boson with unprecedented precision. A major challenge for the CEPC detectors is achieving a boson mass resolution (BMR) of 4%, which is required to separate the Higgs, Z, and W bosons in their hadronic decays. The baseline design of the CEPC detector was guided by the particle flow algorithm (PFA) concept to satisfy the BMR requirements. The BMR performance obtained by the PFA approach is primarily determined by the shower separation capability and energy resolution of calorimeters in detector system. Both electromagnetic and hadronic calorimeter with high granularity are crucial to meet requirements of separating decay channels by optimizing energy resolution for the desired BMR. Scintillator-based electromagnetic and hadronic calorimeter with analogue readout are potential calorimeter scheme candidates for the CEPC detector. In this presentation, a scintillator tungsten electromagnetic calorimeter (ScECAL) prototype and an analogue hadron calorimeter (AHCAL) prototype will be introduced, where the performance and validation of ScECAL and AHCAL based on Monte Carlo simulations and beam test data, including the energy response to high energy electrons in the range of 1-100 GeV/c are contained.
时间投影室(Time Projection Chamber)技术,是利用粒子径迹产生电离电子的漂移时间和漂移方向的投影位置确定径迹三维重建的探测器技术,探测中除可以读出电离信号外, 还可读取粒子的漂移时间, 从而精确确定粒子径迹。近年来,时间投影室技术发展很快,已应用于大型高能物理实验,作为正负电子对撞机的大体积中心探测器及多径迹精密测量方面备受重视。也发展了用于粒子天体物理领域内中微子研究的时间投影室等。
自2010年,中国科学院高能物理研究所加入(Lepton Collider Time Projection Chamber, LCTPC)国际合作组以来,积极踊跃的开展该技术各种应用研究。比如面对下一代环形高能正负电子对撞机物理研究,时间投影室已作为下一代环形正负电子对撞机技术设计报告(Technical Design Report, TDR)的基准主径迹探测器,该技术具有低物质量、高占空比、三维高精度长径迹重建和良好粒子鉴别能力,为满足在高亮度运行时具备高空间分辨率和出色的粒子鉴别(PID)能力,本课题组完成了大量模拟优化研究、实验研究解决各种关键技术问题,已完成正离子流控制(IBF$\times$Gain$\leq$1) 、紫外激光径迹($\lt$100$μ$m ) 和粒子鉴别PID ($\lt$3.6%)技术应用研究。利用Cluster Counting分析技术可有效提升粒子鉴别能力。比如台山中微子实验物理要求:200keV - 1MeV中微子探测,输入反应堆中微子能谱能量分辨率好于$\lt$10%。反应堆裂变产生的中微子穿过TPC探测器,会与气体中自由电子发生弹性散射产生离径迹,通过探测电子电离能量及气体中散射方向重建中微子能谱,深入研究中微子性质;课题组已成功研制出一套充入高气压10atm的CF$_4$工作气体时间投影室原型机。本报告将给出高能物理研究所在正负电子对撞及中微子物理中,时间投影室技术应用研究的最新进展。
超级τ-粲装置(STCF)是中国粒子物理学界提出的一种工作在2~7GeV质心能量下的电子-正电子对撞机。它将为探索τ-粲物理、奇特强子态和超出标准模型的物理提供一个平台。对于该装置,在整个动量范围内进行粒子鉴别(PID)是至关重要的。STCF的PID系统位于电磁量能器和主漂移室之间,并专注于高动量的带电强子,从约0.7GeV/c到2GeV/c。环形成像切伦科夫(RICH)探测器是可以在圆筒区域满足这些要求的技术之一。
本报告给出了PIDB RICH探测器的结构设计,研究了RICH探测器的预期性能。其将使用全氟己烷作为切伦科夫辐射体,碘化铯作为光阴极;并使Micro-Megas联合AGET电子学进行信号读出。通过Geant4模拟给出的结果显示该设计下RICH重建方法可以满足STCF对于强子PID的要求。此外,本报告还将介绍探测器原理样机的制作,性能测试及宇宙线实验的最新结果。
近年来,高能物理领域对味物理和Higgs物理探测需求不断提高,下一代环形高能正负电子对撞机加速器对撞亮度设计也不断提升。中国的CEPC和欧洲FCC-ee均作为高亮度Higgs粒子和Z粒子工厂,在Z峰值的对撞亮度已达到$10^{36}cm^{-2}s^{-1}$。时间投影室在正负电子对撞机实验的概念设计报告(CDR)、技术设计报告(TDR)中均作为基准主径迹探测。相对于传统大尺寸Pad型读出采用毫米级设计(如:$1\,mm\times6\,mm$),新发展的像素型时间投影室技术(Pixel TPC)是目前国际合作组ECFA和LCTPC重要技术研发方向和研究热点。为满足在高亮度运行时具备高空间分辨率和出色的粒子鉴别(PID)能力,同时考虑TPC端盖读出通道数和总功耗等技术参数,需要完成深入的模拟和大量的实验研究。
在中国科学院高能物理研究所,本课题组针对该研究热点,并解决这些关键技术问题。首先通过模拟和实验研究,主要解决以下两个问题:一是像素型读出技术的粒子分辨能力及Cluster Counting数据分析验证,二是保证物理目标前提下,优化设计像素单元读出尺寸。基于Garfield++和Geant4搭建的CEPC Pixel TPC模拟软件框架。该框架分为数字化和数据重建两个部分,数字化部分对主要的电离、漂移、扩散和读出放大等过程进行了参数化;数据重建部分包括事例查找、径迹重建,并利用簇团计数实现探测器性能的优化。通过探测效率的模拟研究分析了簇团计数的优势,结果显示出高颗粒度读出具有明显优势。同时本课题组与DRD1、LCTPC国际合作组合作,基于已研制的TEPix芯片设计TPC读出模块,将在德国DESY开展像素读出的束流实验研究。本报告将给出详细的研究现状和最新研究进展。
新一代正负电子对撞机——超级陶粲装置(STCF)的设计对撞亮度大于 0.5×10$^{35}$cm$^{-2}$ s$^{-1}$,预期事例率达到 400kHz,新装置上强辐照和高计数率的实验条件对外径迹探测器主漂移室(MDCH)提出了严峻挑战。研究人员对MDCH系统进行了详细设计和优化,包括整体机械及应力分析,超小单元的技术攻关,电极丝的高密度排布和固定方法研究,新定位子及穿丝工艺验证、丝张力控制及丝张力测量研究,电子学信号仿真,读出电子学架构及探测器时间与电荷测量方法研究,为未来STCF中MDCH工程机的研制提供了技术基础。