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Event plane determination from the zero degree calorimeter at the cooling storage ring external-target experiment

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nuclear Science and Techniques 2023年第7期34卷 113-121页

作者： Li-Ke Liu Hua Pei Ya-Ping Wang Biao Zhang nu xu Shu-Su Shi Key Laboratory of Quark and Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China

The Cooling Storage Ring external-target experiment(CEE)spectrometer is used to study the nuclear matter created in heavy-ion collisions at√sNN=2.1-2.4 GeV with the aim to reveal the quantum chromodynamics phase structure in the high-baryon-density *** flow is considered an effective probe for evaluating the properties of media during high-energy nuclear *** of the main functions of the zero-degree calorimeter(ZDC),a subdetector system in the CEE,is to determine the reaction plane in heavy-ion *** step is crucial for measuring the collective flow and other reaction-plane-related *** this paper,we illustrate the procedures for event plane determination using the ***,isospin-dependent quantum molecular dynamics model-based predictions of the rapidity dependence of the directed and elliptical flows for p,d,t,3He,and 4He,produced in 2.1 GeV U+U collisions,are presented.

关键词： QCD phase structure Heavy-ion collisions Collective flow Reaction plane Zero-degree calorimeter

Classifier for centrality determination with zero-degree calorimeter at the cooling-storage-ring external-target experiment

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nuclear Science and Techniques 2023年第11期34卷 168-173页

作者： Biao Zhang Li‑Ke Liu Hua Pei Shu‑Su Shi nu xu Ya‑Ping Wang Key Laboratory of Quark and Lepton Physics(MOE)and Institute of Particle Physics Central China Normal UniversityWuhan 430079China

The zero-degree calorimeter(ZDC)plays a crucial role toward determining the centrality in the Cooling-Storage-Ring External-target Experiment(CEE)at the Heavy Ion Research Facility in Lanzhou.A boosted decision tree(BDT)multi-classification algorithm was employed to classify the centrality of the collision events based on the raw features from ZDC such as the number of fired channels and deposited *** data from simulated^(238)U+^(238)U collisions at 500 MeV∕u,generated by the IQMD event generator and subsequently modeled using the GEANT4 package,were employed to train and test the BDT *** results showed the high accuracy of the multi-classification model adopted in ZDC for centrality determination,which is robust against variations in different factors of detector geometry and *** study demon-strates the good performance of CEE-ZDC in determining the centrality in nucleus-nucleus collisions.

关键词： ZDC Boosted decision trees Multi-classification IQMD Centrality determination

NνDEx-100 conceptual design report

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nuclear Science and Techniques 2024年第1期35卷 18-33页

作者： Xi-Guang Cao Yan-Long Chang Kai Chen Emilio Ciuffoli Li-Min Duan Dong-Liang Fang Chao-Song Gao Surja K.Ghorui Peng-Chong Hu Qiang Hu Si-Yuan Huang Ze-Yu Huang Lei Lang Yu-Lan Li Zhi-Jie Li Tian-Yu Liang Jun Liu Chen-Gui Lu Fa-Tai Mai Yuan Mei Hao Qiu Xiang-Ming Sun Xiao-Xing Tang Hu-Lin Wang Qian-Ming Wang Le Xiao Mu-Yun Xiao Jian-Yu Xin nu xu Peng Yang Yi-Chen Yang Zhen Yang Zong-Yang Yu Dong-Liang Zhang Jun-Wei Zhang Cheng-Xin Zhao Dou Zhu NνDEx-100 collaboration Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China Lanzhou University Lanzhou 730000China Central China Normal University Wuhan 430079China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Lawrence Berkeley National Laboratory BerkeleyCA 94720USA North China University of Water Resources and Electric Power Zhengzhou 450045China 不详

Observing nuclear neutrinoless double beta (0vββ) decay would be a revolutionary result in particle *** such a decay would prove that the neutrinos are their own antiparticles,help to study the absolute mass of neutrinos,explore the origin of their mass,and may explain the matter-antimatter asymmetry in our universe by lepton number *** propose developing a time projection chamber (TPC) using high-pressure ^(82)SeF_(6) gas and Topmetal silicon sensors for readout in the China Jinping Underground Laboratory (CJPL) to search for neutrinoless double beta decay of82Se,called the NvDEx *** being located at CJPL with the world’s thickest rock shielding,NvDEx combines the advantages of the high Qββ(2.996 MeV) of82Se and the TPC’s ability to distinguish signal and background events using their different topological *** makes NvDEx unique,with great potential for low-background and high-sensitivity 0 vββ***-100,a NvDEx experiment phase with 100 kg of SeF_(6)gas,is being built,with plans to complete installation at CJPL by *** report introduces 0 vββ physics,the NvDEx concept and its advantages,and the schematic design of NvDEx-100,its subsystems,and background and sensitivity estimation.

关键词： Neutrinoless double beta decay Time projection chamber ^(82)SeF_(6) China Jinping Underground Laboratory

Characteristics of microseismic b-value associated with rock mass large deformation in underground powerhouse caverns at different stress levels

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Journal of Central South University 2022年第2期29卷 693-711页

作者： LI Biao DING Quan-fu xu nu-wen DAI Feng xu Yuan QU Hong-lue School of Geoscience and Technology Southwest Petroleum UniversityChengdu 610500China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of Hydraulics and Mountain River Engineering College ofWater Resource and HydropowerSichuan UniversityChengdu 610065China Department of Engineering Science University of OxfordOX51PFUnited Kingdom

Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest *** the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring *** MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress *** MS b-values associated with rock mass large deformation and their temporal variation are *** results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress *** to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 *** results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.

关键词： underground powerhouse caverns rock mass large deformation stress level microseismic monitoring bvalue

Formation mechanism of rockburst in deep tunnel adjacent to faults:Implication from numerical simulation and microseismic monitoring

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Journal of Central South University 2022年第12期29卷 4035-4050页

作者： CHEN Yi-yi XIAO Pei-wei LI Peng ZHOU Xiang LIANG Zheng-zhao xu nu-wen State Key Laboratory of Hydraulics and Mountain River Engineering(Sichuan University) Chengdu 610065China College of Water Resource and Hydropower Sichuan UniversityChengdu 610065China CHN Energy Dadu River Hydropower Development Co. Ltd.Chengdu 610041China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

Rockbursts were frequently encountered in the construction of deeply buried tunnels at the Jinping-II hydropower station, Southwest China. In those cases, the existence of large structural planes, such as faults, was usually observed near the excavation boundaries. The formation mechanism of the “11·28” rockburst, which was a typical rockburst and occurred in a drainage tunnel under a deep burial depth, high in-situ stress state and complex geological conditions, has been difficult to explain. Realistic failure process analysis(RFPA3D) software was adopted to numerically simulate the whole failure process of the surrounding rock mass around the tunnel subjected to excavation. The spatial distribution of acoustic emission derived from numerical simulation contributed to explaining the mechanical responses of the process. Analyses of the stress, safety reserve coefficient and damage degree were performed to reveal the effect of faults on the formation of rockbursts in the deep tunnel. The existence of faults results in the formation of stress anomaly areas between the tunnel and the fault. The surrounding rock mass failure propagates toward the fault from the initial failure, to different degrees. The relative positions and angles of faults play significant roles in the extent and development of surrounding rock mass failure, respectively. The increase in the lateral stress coefficient leads to the aggravation of the surrounding rock mass damage, especially in the roof and floor of the tunnel. Moreover, as the rock strength-stress ratio increases, the failure mode of the near-fault tunnel gradually changes from the stress-controlled type to the compound-controlled type. These findings were consistent with the microseismic monitoring results and field observations, which was helpful to understand the mechanical behavior of tunnel excavation affected by faults. The achievements of this study can provide some references for analysis of the failure mechanisms of similar d

关键词： near-fault tunnel rockburst numerical simulation formation mechanism microseismic monitoring

Search for the QCD critical point with fluctuations of conserved quantities in relativistic heavy-ion collisions at RHIC： an overview

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nuclear Science and Techniques 2017年第8期28卷 1-40页

作者： Xiaofeng Luo nu xu Institute of Particle Physics and Key Laboratory of Quark andLepton Physics (MOE) Central China Normal UniversityWuhan 430079 China Department of Physics and Astronomy University ofCalifomia Los Angeles CA 90095 USA nuclear Science Division Lawrence Berkeley NationalLaboratory Berkeley CA 94720 USA

Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error *** on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.

关键词：高能重离子碰撞 QCD相变 RHIC 临界点守恒量波动搜索相对论重离子碰撞

Light nuclei production in Au+Au collisions at √^(s)NN=3 GeV from coalescence model

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Chinese Physics C 2023年第7期47卷 133-137页

作者：许月何熊宏许怒 Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

The nucleon coalescence model is one of the most popular theoretical models for light nuclei production in high-energy heavy-ion *** production of light nuclei d,t,^(3)He,and^(4)He is studied using the transport model JAM with a simplified afterburner coalescence at√^(s)NN=3 GeV Au+Au *** scan the cut-off of phenomenological coalescence parameters,i.e.,the relative spatial distance△R and momentum difference△P,for the formation of light nuclei by nucleon coalescence to reproduce the light nuclei pTspectra measured by the STAR *** results indicate a potential connection between the coalescence parameters and the binding energy as well as the diameter of these light nuclei.

关键词： nucleon coalescence light nuclei heavy-ion collision

An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction

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Journal of Mountain Science 2017年第6期14卷 1161-1173页

作者： HOU Tian-xing xu Qiang XIE Hong-qiang xu nu-wen ZHOU Jia-wen State Key Laboratory of Hydraulics and Mountain River Engineering Siehuan University Chengdu 610065 China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology Chengdu 610059 China College of Water Resource and Hydropower Sichuan University Chengdu 610065 China

Mountain hazards with large masses of rock blocks in motion – such as rock falls, avalanches and landslides – threaten human lives and structures. Dynamic fragmentation is a common phenomenon during the movement process of rock blocks in rock avalanche, due to the high velocity and impacts against obstructions. In view of the energy consumption theory for brittle rock fragmentation proposed by Bond, which relates energy to size reduction, a theoretical model is proposed to estimate the average fragment size for a moving rock block when it impacts against an obstruction. Then, different forms of motion are studied, with various drop heights and slope angles for the moving rock block. The calculated results reveal that the average fragment size decreases as the drop height increases, whether for free-fall or for a sliding or rolling rock block, and the decline in size is rapid for low heights and slow for increasing heights in the corresponding curves. Moreover, the average fragment size also decreases as the slope angle increases for a slidingrock block. In addition, a rolling rock block has a higher degree of fragmentation than a sliding rock block, even for the same slope angle and block volume. Finally, to compare with others' results, the approximate number of fragments is estimated for each calculated example, and the results show that the proposed model is applicable to a relatively isotropic moving rock block.

关键词： Rock block Rock fragmentation Rock movement process Crushing work ratio Average fragment size

Excavation-induced microseismicity: microseismic monitoring and numerical simulation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第6期13卷 445-460页

作者： nu-wen xu Chun-an TANG Hong LI Feng DAI Ke MA Jing-dong SHAO Ji-chang WU State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resources and Hydropower Siehuan UniversityChengdu 610065China Institute o fRock Instability and Seismicity Research Dalian University of TechnologyDalian 116024China HydroChina Chengdu Engineering Corporation Chengdu 610072China China Guodian Dadu River Dagangshan Hydropower Development Co. Ltd.Ya'an 625409China

The volume of influence of excavation at the right bank slope of Dagangshan Hydropower Station, southwest China, is essentially determined from microseismic monitoring, numerical modeling and conventional measurements as well as in situ observations. Microseismic monitoring is a new application technique for investigating microcrackings in rock slopes. A micro- seismic monitoring network has been systematically used to monitor rock masses unloading relaxation due to continuous exca- vation of rock slope and stress redistribution caused by dam impoundment later on, and to identify and delineate the potential slippage regions since May, 2010. An important database of seismic source locations is available. The analysis of microseismic events showed a particular tempo-spatial distribution. Seismic events predominantly occurred around the upstream slope of 1180 m elevation, especially focusing on the hanging wall of fault XL316-1. Such phenomenon was interpreted by numerical modeling using RFPA-SRM code （realistic failure process analysis-strength reduction method）. By comparing microseismic activity and results of numerical simulation with in site observation and conventional measurements results, a strong correlation can he obtained between seismic source locations and excavation-induced stress distribution in the working areas. The volume of influence of the rock slope is thus determined. Engineering practices show microseismic monitoring can accurately diagnose magnitude, intensity and associated tempo-spatial characteristics of tectonic activities such as faults and unloading zones. The integrated technique combining seismic monitoring with numerical modeling, as well as in site observation and conventional surveying, leads to a better understanding of the internal effect and relationship between microseismic activity and stress field in the right bank slope from different perspectives.

关键词： Microseismic monitoring Rock slope numerical simulation Stability analysis Dagangshan Hydropower Station