Current Articles

2020, Volume 37,  Issue 3

Special Issue of the 17th Conference on Nuclear Physics in China(CNPC2019)

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2020, 37(3)
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Invited Plenary Presentations
Transport of Isospin Degree of Freedom in Heavy Ion Reactions and the Constraint of Symmetry Energy
Zhigang XIAO
2020, 37(3): 249-259. doi: 10.11804/NuclPhysRev.37.2019CNPC63
Abstract(138) HTML (42) PDF (4086KB)(32)
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Heavy ion reactions provide an effective tool to study the nuclear equation of state (EOS) in terristial laborartory. When the number of neutrons differs largely with the number of protons in a nuclear system or nuclei, the main contribution to the nuclear EOS comes from the symmetry energy term. The nuclear symmetry energy, reflecting the isovector sector of the nucleon-nucleon potential, is closely relevant to the structural properties of dense object and the merging process in stellar environments, as well as to the exotic properties of nuclei and the location of the board of nuclear chart. However, the density dependence of the nuclear symmetry energy is the most unknown ingredient in the properties of nuclear matter so far. Thus the investigation of nuclear symmetry energy in wide density range becomes the main frontiers in many world-level nuclear laboratories and astrophyics observatories. In this article, we review briefly the experimental progress in this field. Particularly the experimental studies on the transport of the isospin degree of freedom in heavy ion reactions and the constraint of nuclear symmetry energy based on the Heavy Ion Research Facity at Lanzhou (HIRFL) are introduced. It has been shown that the isospin drift process persists to the late stage of the reaction, indicating that the isospin transport time scale may depend on the physics process under investigation. Due to the long-time accumulation of isospin effects, the angular distribution of the isospin concentration of the light particles in a wide range of angle is a sensitive probe of nuclear symmetry energy. With \begin{document}${S}\!=\!28.3\,\mathrm{M}\mathrm{e}\mathrm{V}$\end{document} fixed at saturation point, the slope of the symmetry energy depending on density is contrained in the range of \begin{document}$L\!=\!33\!\sim\!61\,\mathrm{M}\mathrm{e}\mathrm{V}$\end{document} at \begin{document}$ \mathrm{C}\mathrm{L}\!=\!95$\end{document}%. Using a Compact Spectrometer for Havy Ion Experiment (CSHINE) with ability to achieve isotopic particle identification and fission event reconstruction, the small angle correlation function of the isotope-resolved light charged particles can be measured to derive the time scale of isospin relaxation in heavy ion reactions at Fermi energies. In the last section of the article, the isovector orientation effect of the polarized deuteron beam scattering off heavy target is introduced, which offers a novel means to constrain the nuclear symmetry energy below saturation density.
Threshold Phenomena and Signals for Exotic Hadrons
Qiang ZHAO
2020, 37(3): 260-271. doi: 10.11804/NuclPhysRev.37.2019CNPC78
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We present a brief review of some topical issues in the study of QCD exotic hadrons. A special emphasis of the threshold phenomena is made by taking into account the implementation of the effective field theory study of hadronic molecules and the impact arising from the triangle singularity. A combined analysis may provide some clues towards a better understanding of the hadron spectroscopy.
MAGIC: Matter in Astrophysics, Gravitational Waves, and Ion Collisions
Motornenko Anton, Hanauske Matthias, Weih Lukas, Steinheimer Jan, Stöcker Horst
2020, 37(3): 272-282. doi: 10.11804/NuclPhysRev.37.2019CNPC75
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The gravitational waves emitted from a binary neutron star merger, as predicted from general relativistic magneto-hydrodynamics calculations, are sensitive to the appearance of quark matter and the stiffness of the equation of state of QCD matter present in the inner cores of the stars. These astrophysically created extremes of thermodynamics do match, to within 20%, the values of densities and temperatures which are found in relativistic heavy ion collisions, if though at quite different rapidity windows, impact parameters and bombarding energies of the heavy nuclear systems. In this article we combine the results obtained in general relativistic simulations of binary neutron star systems with ones from heavy ion collisions in the lab to pin down the EOS and the phase structure of dense matter. We discuss that the postmerger gravitational wave emission of the neutron star merger remnant might give, in the near future, insides about the properties of the hadron quark transition.
Progress of the Ground Experiments of Jinping Underground Nuclear Astrophysics Experiment
Weiping LIU, Zhihong LI, Jianjun HE, Xiaodong TANG, Gang LIAN, Bing GUO, Jun SU, Yunju LI, Baoqun CUI, Liangting SUN, Qi WU, Zhu AN, Yangping CHEN, Zhijun CHEN, Xianchao DU, Changbo FU, Lin GAN, Guozhu HE, Heger Alexander, Suqing HOU, Hanxiong HUANG, Ning HUANG, Liyang JIANG, Kubono Shigeru, Jianmin LI, Kuoang LI, Tao LI, Lugaro Maria, Xiaobing LUO, Shaobo MA, Zhiyu HAN, Xinyue LI, Tianli MA, Dongming MEI, Weike NAN, Wei NAN, Chen CHEN, Hao ZHANG, Long ZHANG, Fuqiang CAO, Yongzhong QIAN, Jiuchang QIN, Jie REN, Wanpeng TAN, Tanihata Isao, Peng WANG, Shuo WANG, Youbao WANG, Shiwei XU, Shengquan YAN, Zhi ZENG, Xiangqing YU, Qian YUE, Sheng ZENG, Huanyu ZHANG, Hui ZHANG, Litao YANG, Liyong ZHANG, Ningtao ZHANG, Qiwei ZHANG, Tao ZHANG, Xiao FANG, Xiaopeng ZHANG, Xuezhen ZHANG, Yunhua CHEN, Ningchun QI, Shiyong WU, Xuyuan GUO, Jifang ZHOU, Shengming HE, Jinhua NING, Jianfeng YUE
2020, 37(3): 283-290. doi: 10.11804/NuclPhysRev.37.2019CNPC60
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A number of nuclear reactions such as \begin{document}$^{25}{\rm{Mg}}{({\rm{p}},\gamma )^{26}}{\rm{Al}}$\end{document}, \begin{document}$^{13}{\rm{C}}{(\alpha ,{\rm{n}})^{16}}{\rm{O}}$\end{document}, \begin{document}$^{12}{\rm{C}}{(\alpha ,\gamma )^{16}}{\rm{O}}$\end{document} and \begin{document}$^{19}{\rm{F}}{({\rm{p}},\alpha )^{16}}{\rm{O}}$\end{document} will be measured directly down to the Gamow window energy range in Jinping Underground Nuclear Astrophysics (JUNA) Experiment, taking the advantage of the ultra-low background in China Jinping Unerground Laboratory (CJPL). The measurements can provide updated data for understanding the evolution of stars and the origin of elements. Up to now, tests of accelerator, beam, targets, detectors, and electronics have been performed systematically on the ground. The high-purity germanium detectors efficiency calibration, 304 keV resonance strengths measurement in \begin{document}$^{25}{\rm{Mg}}$\end{document}(p, \begin{document}${\rm{\gamma}}$\end{document})26Al, \begin{document}$^{19}{\rm{F}}{({\rm{p}},\alpha )^{16}}{\rm{O}}$\end{document} cross section measurement, neutron detector design, production and efficiency calibrationas as well as target design and stability test are included as overground experiments. The Whole JUNA project is going smoothly in general. A series of key progresses and primary results have been reached on the ground. Underground experiments in the JUNA project will be carried out in order and reach the prospected goals in the near future. Broader international cooperation will also be promoted, supporting the solution of several major scientific problems in the evolution of cosmogony.
Exotic Nuclear Structure of Neutron-rich Zn Isotopes
Shujing WANG, Shiwei BAI, Xiaofei YANG
2020, 37(3): 291-300. doi: 10.11804/NuclPhysRev.37.2019CNPC34
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Nuclear structure of unstable nuclei, in particularly the nuclei near the magic number, has been one of the hot topics of nuclear physics study. Near the neutron magic number N=40, 50, rich nuclear structure phonomania appeared in the nickel region, in particularly for the neutron-rich isotopes, have stimulated intensive investigation from both theoretical and experimental aspects. In order to gain a better understanding of the nuclear structure in the nickel region, we choose to study the properties of neutron-rich Zn(Z=30) isotopes. In this paper, after a simple introduction of the laser spectroscopy experiment of Zn isotopes at CERN-ISOLDE, we reviewed the nuclear spins, magnetic moment, electric quadrupole moment and root mean square charge radius of the ground and long-lived isomeric states of 62–80Zn isotopes. Based on these properties, together with shell-model calculation from different interactions, we discussed systematically the nuclear structure phenomena, such as the shell structure evolution, magicity, deformation and shape coexistence, and the cross-shell excitation of correlated nucleons. At the end, on the basis of the current experimental data and nuclear structure information, as well as the theoretical prediction of energy level evolution of N=51 isotones in nickel region, we propose to measure the basic properties of 81,82Zn nuclei at the collinear resonance ionization spectroscopy setup at ISOLDE-CERN.
Progress of Isochronous Mass Spectrometry at HIRFL-CSR
Hanyu DENG, Meng WANG, Yuhu ZHANG, Chaoyi FU, Xu ZHOU, Mingze SUN, Yuanming XING, Min ZHANG
2020, 37(3): 301-308. doi: 10.11804/NuclPhysRev.37.2019CNPC40
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In recent years, high-precision mass measurements of short-lived nuclides were conducted using isochronous mass spectrometry (IMS) based on the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). The new data enable us to discuss some related physical problems in the realm of nuclear structure and astrophysics. In this contribution, details of the measurements and data analysis are described. The IMS with two Time-Of-Flight (TOF) detectors is mainly introduced. In order to improve the mass resolving power while preserving the acceptance of the storage ring, additional velocity information beside the revolution time in the ring is obtained for each of the stored ions by using the double TOF detector system. The IMS with two TOF detectors is a brand new concept, and relevant experimental techniques need to be developed. We have established a simulation platform based on CSRe, developed high-performance TOF detectors and installed them in a straight section of the CSRe, performed online beam testing, developed new ion optics and optimized them, and developed data analysis methods and optimized them. Furthermore, planned technical developments are outlined in this contribution.
Progress and Prospects of Nuclear Data Research and Its Application
Zhigang GE, Yongjing CHEN
2020, 37(3): 309-316. doi: 10.11804/NuclPhysRev.37.2019CNPC42
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All data related to nucleus are referred to as nuclear data, which include nuclear reaction data describing the interaction between incident particle and nucleus, nuclear structure data and radioactive decay data characterizing the properties of nucleus. Nuclear data are the basic data for nuclear physics fundamental research, nuclear energy utilization, nuclear facilities construction and nuclear technology application. Nuclear data are also widely applied in nuclear medicine, material analysis, resource exploration, environmental monitoring, aerospace technology and nuclear astrophysics research fields. This paper briefly introduces the types of nuclear data, the generation process and application of nuclear data, then reviews the development of international nuclear data and the current status of nuclear data research in China. Finally some suggestions for the future development of nuclear data in China are given.
Soft and Hard Probes of Relativistic Heavy-Ion Collisions
Guangyou QIN
2020, 37(3): 317-328. doi: 10.11804/NuclPhysRev.37.2019CNPC39
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We provide a short review on some recent developments in the soft and hard probes of quark-gluon plasma(QGP) in high-energy nuclear collisions. The main focus is on the theoretical and phenomenological studies of anisotropic collective flow and jet quenching related to the Relativistic Heavy-Ion Collider(RHIC) and the Large Hadron Collider(LHC). The origin of the collectivity in small collision systems is also briefly discussed. For soft probes, we discuss initial-state fluctuations and geometric anisotropy, the hydrodynamic evolution of the fireball, and final-state anisotropic flows, flow fluctuations, correlations and longitudinal decorrelations. Systematic comparison to experimental data may infer the evolution dynamics and various transport properties of the QGP produced in heavy-ion collisions. For hard probes, we focus on the flavor dependence of parton energy loss and jet quenching, the hadronization of heavy quarks in QGP, full jet evolution in nuclear medium and medium response. Detailed analysis of related observables can help us achieve more comprehensive understanding of jet-medium interaction and heavy flavor production in relativistic nuclear collisions. For small systems, we discuss how initial-state and final-state effects explain the observed collective flows of light and heavy flavor hadrons in proton-nucleus collisions, which is helpful in understanding the origin of the collectivity in large collision systems.
Symmetries and Their Breaking of Strong Interaction System
Yuxin LIU
2020, 37(3): 329-363. doi: 10.11804/NuclPhysRev.37.2019CNPC77
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This article reviews concisely the symmetries and their breaking of strong interaction system. To establish the bridge between the abstract symmetry concept and principle in mathematics and the application in physics to reveal the underlying principle of strong interaction, we describe not only the abstract concept but also the realization of the unitary and other symmetries with the microscopic particles. We then describe the evolution of the strong interaction matter in the early universe in view of the symmetries and their breaking, especially on the dynamical generation of the observable mass(i.e., DCSB) and those of the strong and other interactions (gauge symmetry and breaking). We make also a survey of the symmetries and their breaking of nucleus, with concentration on the general methods of studying the many-body system in the symmetry point of view, the multi-particle shell model and the interacting boson approximation (IBM), the modes of nuclear collective motion and their evolution (i.e., nuclear shape phase transition). The survey intends to link the fundamental approaches with the practical investigations in the related frontiers of research properly and promptly.
Current Status and Future Prospect of Neutron Facilities at China Advanced Research Reactor
Tianfu LI, Meimei WU, Xuesheng JIAO, Kai SUN, Dongfeng CHEN
2020, 37(3): 364-376. doi: 10.11804/NuclPhysRev.37.2019CNPC36
Abstract(1731) HTML (13) PDF (65201KB)(16)
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Neutron research facilities have been built on the high flux neutron source China Advanced Research Reactor(CARR), of which different kinds of neutron techniques, including neutron scattering, neutron imaging and neutron activation analysis, are now available. The neutron scattering instruments, including neutron diffractometers, small-angle neutron scattering, neutron reflectometer, inelastic neutron scattering spectrometers, can be used to analyze the microstructure and dynamic properties of materials. The thermal neutron imaging and cold neutron imaging facilities can be used for the non-destructive testing of defects inside materials. And neutron activation analysis systems are powerful for the detection of different elements or isotopes. There are now 19 neutron instruments which have been built or under construction. Some sample environment devices are also available. These facilities provide important support for both fundamental scientific researches and industrial applications in the fields of physics, chemistry, material science, life science, energy, environment and so on. CARR neutron research facilities will continue to open to the users from outside the institute, to not only serve scientific frontier researches, but also meet the major national innovation needs.
Feasibility Study on the Deep Dirac Levels with High-Intensity Lasers
Changbo FU, Xiaopeng ZHANG, Dechang DAI
2020, 37(3): 377-381. doi: 10.11804/NuclPhysRev.37.2019CNPC20
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Various theories have predicted the deep Dirac levels (DDLs) in atoms for many years. However, the existence of the DDL is still under debating, and need to be confirmed. With the development of high intensity lasers, nowadays, electrons can be accelerated to relativistic energies by high intensity lasers. Furthermore, electron-positron pairs can be created, and nuclear reactions can be ignited, which provide a new tool to explore the DDL related fields. In this paper, we propose a new experimental method to study the DDL levels by monitoring nuclei's orbital electron capture life time in plasma induced by high intensity lasers. The present study reveal that if a DDL exists, a nuclear electron capture rate could be enhanced by factor of over \begin{document}$ 10^7$\end{document}, which makes it a very sensitive method for the DDL detecting.
Beyond Mean-field Description of Nuclear Gamow-Teller Resonance and β-decay Half-lives
Yifei NIU
2020, 37(3): 382-390. doi: 10.11804/NuclPhysRev.37.2019CNPC57
Abstract(1462) HTML (36) PDF (3552KB)(12)
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Nuclear β decay is one of the key nuclear processes that determine how the heavy elements from Fe to U in the universe were made. The dominant nuclear process in β-decay is the Gamow-Teller(GT) transition, so the key point for nuclear β-decay study is to describe nuclear GT transition accurately. One of the most widely used nuclear model is random phase approximation (RPA). However, since it only includes one-particle one-hole excitation configurations, this model cannot describe spreading width of GT resonance, and tends to overestimate the β-decay half-lives. To overcome these difficulties, based on Skyrme density functional, the random phase approximation with particle vibration coupling (RPA+PVC) model was developed. Compared to RPA model, it further includes the one-particle one-hole coupled with phonons in its configuration space, which includes many-body correlations beyond mean field approximation. To extend the study to open shell nuclei, the quasiparticle random phase approximation with quasiparticle vibration coupling model (QRPA+QPVC), which includes pairing correlations, was developed. Based on the above models, the GT excitation, β decay, β+/EC of magic nuclei and superfluid nuclei were studied. It is found that with the same Skyrme interaction SkM*, the experimental GT width and transition strength profile were well reproduced, the quenching phenomenon was partly explained, and the description of β-decay half-lives were improved at the same time. The recent progress of this study is reviewed, and in the meantime the perspectives for future developments are given.
Experimental Overview of Recent Research Highlights on International Cooperation in High-energy Nuclear Physics
Xiaoming ZHANG, Daicui ZHOU
2020, 37(3): 391-405. doi: 10.11804/NuclPhysRev.37.2019CNPC79
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Aim of the high-energy nuclear physics experiments is to investigate the production and evolution properties of a new nuclear matter state − the Quark-Gluon Plasma under the extreme conditions of high temperature and energy density. This study brings the unique insight into understanding the deep structure of the current material world and the properties of the strong nuclear force in such ultra hot and dense multi-particle system. It also provides the important opportunity to explore new physics phenomenons under such extreme conditions. In this paper, the main international high-energy nuclear physics experimental projects that China has participated and their physics goals are briefly outlined. The recent highlights of the achievements on investigating the properties of the Quark-Gluon Plasma and on exploring the new physics phenomenons in high-energy heavy-ion collisions made by China are overviewed. The perspective on the experimental research projects for high-energy nuclear physics to the future is given as well.
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2020, 37(3)
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Reports from the Winners of the “Hu Jimin Award of Education and Science”
Triangle Singularities and Charmonium-like XYZ States
Fengkun GUO
2020, 37(3): 406-413. doi: 10.11804/NuclPhysRev.37.2019CNPC52
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The spectrum of hadrons is important for understanding the confinement of quantum chromodynamics. Many new puzzles arose since 2003 due to the abundance of experimental discoveries with the \begin{document}$XYZ$\end{document} structures in the heavy quarkonium mass region being the outstanding examples. Hadronic resonances correspond to poles of the \begin{document}$S$\end{document}-matrix, which has other types of singularities such as the triangle singularity due to the simultaneous on-shellness of three intermediate particles. Here we briefly discuss a few possible manifestations of triangle singularities in the \begin{document}$XYZ$\end{document} physics, paying particular attention to the formalism that can be used to analyze the data for charged \begin{document}$Z_c$\end{document} structures in the \begin{document}$\psi\pi$\end{document} distributions of the reaction \begin{document}$e^+e^-\to \psi\pi^+\pi^-$\end{document}.
Quark Gluon Matter in Strong Magnetic and Vortical Fields
Xuguang HUANG
2020, 37(3): 414-425. doi: 10.11804/NuclPhysRev.37.2019CNPC29
Abstract(188) HTML (82) PDF (9840KB)(51)
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Relativistic heavy-ion collisions generate high-temperature quark gluon plasma with extremely strong electromagnetic and fluid vortical fields. The quark gluon plasma exhibits intriguing macroscopic quantum phenomena in the presence of strong electromagnetic and vortical fields, e.g., the chiral magnetic effect, chiral vortical effects, chiral separation effect, chiral electric separation effect, and spin polarization. These phenomena provide us a unique experimental means to study the nontrivial topological sector of the quantum chromodynamics, e.g., possible parity violation of strong interaction at high temperature, and subatomic spintronics of quark gluon plasma. They are also closely related to other subfields of physics, such as particle physics, condensed matter physics, astrophysics, and cold atomic physics, and thus form a new interdisciplinary research area. The goal of the present article is to give an introduction to these phenomena and to review the current status of their experimental search in heavy-ion collisions. In particular, we find that the magnetic fields generated in heavy-ion collisions can reach \begin{document}$10^{18}\sim 10^{20}$\end{document} G and the fluid vorticity can reach \begin{document}$10^{22}$\end{document} s–1; these are the known strongest magnetic fields and vorticity in the current universe. We quantitatively analyze the isobar collisions and find that, even if the background level is of 93%, the current isobar collisions can still test the occurrence of the chiral magnetic effect at \begin{document}$3\sigma$\end{document} significance level. We give the causal set of equations of spin hydrodynamics and give the collective modes in it; the spin hydrodynamics is useful to resolve the sign problem appearing in the comparison between theoretical calculations and experimental measurements of the spin polarization of hyperons.
Study on Exotic Structure of Light Neutron-rich Nuclei via Direct Reaction
Gen LI, Zhiwei TAN, Jianling LOU, Ying JIANG, Yanlin YE
2020, 37(3): 426-437. doi: 10.11804/NuclPhysRev.37.2019CNPC09
Abstract(273) HTML (119) PDF (4925KB)(30)
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Direct reaction, including elastic scattering, inelastic scattering and transfer reactions, is one of the commonly used methods to study the exotic structure of light neutron-rich nuclei. Taking for example the structure studies of 6,8He, 11Li, 11,12Be, 14,15B, and 15,16C, this paper reviewed how to use these reactions to study the exotic structure of neutron-rich nuclei experimentally. The effective interactions (optical potential) between the halo nuclei 6,8He/11Be and the p/d targets are obtained by fitting the elastic scattering angular distributions. The deformation parameter of 16C is extracted from the inelastic scattering data of 16C+p/d, which indicates that the deformation of 16C can not be ignored. The p-, s- and d-wave intensities of the ground state in 8He and 11,12Be are quantitatively studied by the single-nucleon transfer reaction. The results show that in the ground state of 8He, besides four valence neutrons filling the 0p3/2 orbital, other configurations, such as (0p3/2)2(0p1/2)2, may have some probability. The ground state of 12Be is dominated by the d-wave intruder, but its neighbour 11Be is predominated by the s-wave intruder.
Experimental Measurement Method of Beta Decay Strength of Unstable Nuclei
Jichao ZHANG, Baohua SUN
2020, 37(3): 438-446. doi: 10.11804/NuclPhysRev.37.2019CNPC69
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The β decays of atomic nuclei refer to the transformation that the nuclei emit a β particle or capture an electron. The accurate measurements of the β transition strength functions Sβ(E) are of great significance in exploring the structure of unstable nuclei, revealing the process of stellar nucleosynthesis and also verifying the β decay theories. Experimentally, one way to determine the β transition strength is to directly measure the beta decay product using β-γ coincidence technique and/or total absorption spectroscopy. This method can give the transition information within the Qβ window. Another method to obtain the β decay strength is via the charge exchange reactions performed at the intermediate energy region (100~400 MeV/u), such as (p, n) or (3He, t). This is done by a high-precision measurement of the differential cross section. This method allows to access the transition strength that beyond the Qβ window, however, it is restricted by the beam intensity, and as a consequence hard to perform a systematical study of unstable nucleus with low yields. In view of this, in this paper we proposes a systematic measurement of the total charge exchange reaction cross section of the unstable nuclei. Combined with the well developed nuclear reaction theory, this method may set a constrain to the summed strength of the Gamow-Teller transition of the unstable nuclei within the proton separation threshold. Moreover, we introduce briefly the relevant work that has been carried out and planned.
Shell-Model Explanation on Some Newly Discovered Isomers
Cenxi YUAN, Menglan LIU, Yulin GE
2020, 37(3): 447-454. doi: 10.11804/NuclPhysRev.37.2019CNPC18
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Recently, isomeric states are discovered for the first time in 101In, 123,125Ag, and 218Pa. The nuclear shell model is used to explain the underlying physics in these and related isomers in In, Ag isotopes, and the \begin{document}$N\!=\!127$\end{document} isotones. The observed excitation energies of the \begin{document}$1/2^{-}$\end{document} isomeric states in odd-A In isotopes, 101-109In, are rather similar among five isotopes, which can be explained by introducing the strong neutron configuration mixing between the \begin{document}$0g_{7/2}$\end{document} and \begin{document}$1d_{5/2}$\end{document} orbitals. In addition, from the \begin{document}$9/2^{+}$\end{document} ground state to the \begin{document}$1/2^{-}$\end{document} isomeric state in these odd-A In isotopes, a proton moves from the \begin{document}$1p_{1/2}$\end{document} orbital to the \begin{document}$0g_{9/2}$\end{document} orbital, which may induce the change on the single particle energies of the neutron \begin{document}$0g_{7/2}$\end{document} and \begin{document}$1d_{5/2}$\end{document} orbitals. Such configuration dependent shell evolution in one nucleus is called the type II shell evolution. Similar to In isotopes, the isomeric states in 123,125Ag are found to be the \begin{document}$1/2^{-}$\end{document} states, which correspond to a proton hole in \begin{document}$1p_{1/2}$\end{document} orbital. But \begin{document}$1/2^{-}$\end{document} states are ground states in 115,117Ag, which indicates an inversion of the proton \begin{document}$1p_{1/2}$\end{document} and \begin{document}$0g_{9/2}$\end{document} orbitals around \begin{document}$N\!=\!72$\end{document}. The shell-model analysis shows that the tensor force is the key reason of the inversion of the two orbitals. \begin{document}${\rm A}~1^{-}$\end{document} ground state and a high spin isomeric state are observed previously along the odd-odd \begin{document}$N\!=\!127$\end{document} isotones, 210Bi, 212At, 214Fr, and 216Ac. However, the ground state and the newly discovered isomeric state of 218Pa are suggested to be \begin{document}$8^{-}$\end{document} and \begin{document}$1^{-}$\end{document}, respectively, based on the properties of \begin{document}$\alpha$\end{document} decay and the shell-model calculations. The evolution of the ground states and isomeric states along the odd-odd \begin{document}$N\!=\!127$\end{document} isotones are caused by the transition of the proton-neutron interaction from particle-particle type to hole-particle type and the proton configuration mixing. In general, the nuclear shell model gives nice descriptions on these newly discovered isomeric states in nuclei around the doubly magic nuclei 100Sn, 132Sn, and 208Pb. The isomeric states in nuclei around doubly magic nuclei, so called the shell-model isomers, are of high importance in the nuclear structure study, because they often provide the first spectroscopic properties in the extreme neutron-rich and neutron-deficient nuclei in the medium and heavy mass region and include a plenty of information in physics, such as the proton-neutron interaction and its role in shell evolution.
α Decay Studies on New Neutron-deficient Np Isotopes
Zhiyuan ZHANG, Zaiguo GAN, Huabin YANG, Long MA, Minghui HUANG, Chunli YANG, Mingming ZHANG
2020, 37(3): 455-461. doi: 10.11804/NuclPhysRev.37.2019CNPC44
Abstract(213) HTML (69) PDF (5526KB)(33)
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In contemporary nuclear research field, it is of special interest to synthesize the new isotopes far from the stability line and to explore the existing limit of nuclei. For the most proton-rich N≈126 isotones, which are located near the crossing point between the proton drip line and the N=126 closed shell, synthesizing and α-decay studies may shed new light on the structural evolution of the N=126 shell closure. Based on measurements at the gas-filled recoil separator SHANS, the most neutron-deficient new isotopes, 219,220,223,224Np, were synthesized via 36,40Ar+185,187Re fusion-evaporation reactions. The new experimental results allow us to establish the α-decay systematics for Np isotopes around N=126 for the first time, and to test the robustness of this shell closure in neptunium. The systematic analysis of single proton separation energies figures out the exact location of the proton drip line in Np isotopic chain. At the same time, the isotope 219Np was identified as the presently known heaviest nuclide beyond the proton drip line. In addition, the possibility of producing other new isotopes (218,221,222Np) in this region is discussed in terms of the measured cross sections and the theoretical predictions.
Investigation of Edge Plasma Instabilities in High Confinement Plasmas of Tokamak
Wulyu ZHONG, Xuru DUAN
2020, 37(3): 462-469. doi: 10.11804/NuclPhysRev.37.2019CNPC05
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In tokamak plasmas, the confinement performance can be significantly improved in high confinement regime. Investigation on the plasma instabilities in this regime is important for the confinement control and steady state operation of tokamak. This paper mainly introduces the researches on the high confinement mode and underlying edge plasma instabilities. It emphasizes on the studies on high confinement mode transition, features of edge-localized mode and its control, pedestal instabilities and pedestal saturation mechanism. The study suggests that pedestal dynamics and edge-localized mode might be actively controlled by the pedestal turbulence, resulting in the steady state operation both with high confinement performance and low heat loads on plasma facing components.
A Study of the Kaon from the Basis Light-Front Quantization Approach
Kaiyu FU, Hengfei ZHAO, Jiangshan LAN, Xingbo ZHAO
2020, 37(3): 470-477. doi: 10.11804/NuclPhysRev.37.2019CNPC31
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We study the properties of the kaon through the light-front wave function(LFWF) obtained from the Basis Light-front Quantization(BLFQ) approach. Our Hamiltonian contains the kinetic energy terms, a transverse confining potential motivated by the light-front holographic quantum chromodynamics(LFHQCD) model, a complementary longitudinal confining potential, and the quark-gluon interactions based on quantum chromodynamics (QCD). Our basis space includes the lowest two Fock sectors. Based on the previous work, we tune the only additional strange quark mass parameter to match the resulting kaon mass with the experimental data. Based on the obtained leading Fock sector LFWF, we calculate the parton distribution amplitude(PDA) of the kaon which is in reasonable agreement with the one calculated from perturbative QCD in the massless quark limit. The obtained kaon form factor (FF) agrees with results from the Super Proton Synchrotron(SPS) experiment at the European Organization for Nuclear Research (CERN) and the Fermi National Accelerator Laboratory(FNAL) experiment. The electromagnetic radius (at the leading order Fock sector) is comparable to the one from the particle data group(PDG). In addition, the kaon parton distribution function(PDF), after QCD evolution, can be used to calculate the ratio of the kaon up quark PDF to that of the pion whose trend qualitatively agrees with that of the CERN-NA-003 experimental data. The obtained kaon PDF shows that the ratio between longitudinal momentum fractions of valence quarks, \begin{document}$ \langle x_{uv}\rangle/\langle x_{sv}\rangle $\end{document}, is around 2/3, which agrees with results from the Bethe-Salpeter equation(BSE) model and the lattice QCD calculation in the Michigan State University(MSULat). We also calculate the structure function of the kaon which shows disagreement with the one from BLFQ-NJL calculation. This disagreement would be investigated in the future Electron-Ion Collider experiment(EIC).
Parallel Session Presentations-Nuclear structure
Nuclear Shell Structure Properties Described by Relativistic Hartree-Fock Theory
Jia LIU, Jiajie LI, Jing GENG, Wenhui LONG
2020, 37(3): 478-491. doi: 10.11804/NuclPhysRev.37.2019CNPC61
Abstract:
For a long time, nuclear shell structure is an important issue of nuclear physics. In particular, with rapid development of new generation of nuclear radioactive ion beam facilities and detectors, new shell structures appearing in neutron-rich nuclei have largely attracted the interests of the field, including the mechanism behind and the evolutions. Under the frame of relativistic Hartree-Fock theory founded on the meson-exchange diagram of nuclear force, taking calcium isotopes, doubly magic nuclide 208Pb and the selected superheavy and exotic nuclei as examples, this paper reviews the occurrence of new sub-shells in neutron-rich nuclei, the pseudo-spin symmetry (PSS) restoration and the in-medium nuclear attraction-repulsion balance, the PSS restoration/violation and nuclear shell structure, novel phenomena, etc., in which the roles of the Fock terms are intensively discussed.
β-delayed Decay Spectroscopies of Extremely Proton-rich Nuclei in sd-shell
Chengjian LIN, Xinxing XU, Lijie SUN, Huiming JIA, Lei YANG, Dongxi WANG, Nanru MA, Feng YANG, Fupeng ZHONG, Min PAN, Peiwei WEN, Yongjin YAO, Shanhao ZHONG, Tianpeng LUO,   (RIBLL Collaboration)
2020, 37(3): 492-499. doi: 10.11804/NuclPhysRev.37.2019CNPC62
Abstract:
Structure of nucleus far from the β-stability line is a currently hot topic in the field of nuclear physics. The β-decay spectroscopy is an important method to study the nuclear structure, especially for the drip-line nuclei with low yield. This paper reviews the experimental studies of β-delayed decay spectroscopies for the extremely proton-rich nuclei in sd-shell recently carried out at the RIBLL1 facility. The precise data on half-lives, masses of decay daughter nuclei, energy spectra and branch ratios of β-delayed proton and two-proton decays as well as γ transitions for 15 nuclei have been obtained, which greatly enrich the spectroscopy information of the nuclei close to the proton drip-line in this region. In particular, the decay properties of some nuclei like 22Si and 20Mg as well as 27S and 26P are described in detail. Moreover, some hot topics related to the three-body force, the decay asymmetry of mirror nuclei, and the thermomuclear reaction rates related to the super-abundant issue of 26Al in the Milky Way are discussed.
The Nuclear Physics Research of Shandong University at Weihai
Shouyu WANG, Bin QI, Shuo WANG, Jianhua GAO, Chen LIU, Naibo ZHANG, Xingchi HAN
2020, 37(3): 500-508. doi: 10.11804/NuclPhysRev.37.2019CNPC70
Abstract:
This paper reviews the research and recent progress in the fields of nuclear spectroscopy, nuclear astrophysics, detector development, and high energy nuclear physics at Shandong University, Weihai. Specifically, we emphatically introduce the shape coexistence and delayed band crossing in \begin{document}$A\sim110$\end{document} mass region, the "stapler" and "umbrella" bands, measurement of key nuclear reaction in the C-N-O circle, the parameterized equation of state and binary neutron stars merger event, the design and development of charged particle detector, quantum transport theory and high order anomalous transport in relativistic heavy-ion collision. The future research emphases are outlooked.
Shell Model Study of Even-even sd and pf Shell Nuclei With the Pairing Plus Quadrupole-quadrupole Interaction
Yeqiu HE, Guanjian FU
2020, 37(3): 509-515. doi: 10.11804/NuclPhysRev.37.2019CNPC10
Abstract:
In this paper we study low-lying states of even-even nuclei in the sd and pf shells in the framework of the shell model with the phenomenological pairing plus quadrupole-quadrupole (P+Q) interaction. By adopting the single-particle energy and the monopole interaction from the USDB and GXPF1 interactions, the low-lying spectra of spherical nuclei and deformed nuclei are successfully reproduced by a unified set of parameters. We obtain a reasonably good result for binding energies by removing the monopole component from the pairing interactions. The isoscalar pairing interaction does not play an important role in the states. The monopole interaction provides contributions to the empirical proton-neutron interaction, the symmetry energy, and the Wigner energy.
Variational Approach for Pair Determination in Nucleon Pair Approximation
Zhenzhen QIN, Yang LEI
2020, 37(3): 516-522. doi: 10.11804/NuclPhysRev.37.2019CNPC45
Abstract:
We propose a pair-condensation variation approach to evaluate the importance of collective pairs and determine their structure in low-lying states. Based on such a variation, the Nucleon Pair Approximation(NPA) could avoid the collective-pair uncertainty, which the previous NPA calculations have suffered a lot. With the trial calculation for transitional 132Ba, we exemplify the ability of our variation approach. In detail, the variation can be adopted to calculate the quadrupole deformation parameters with non-axisymmetric deformation degree of freedom. It conclusively helps the NPA to decide which collective pair is essential for obtaining a lower yrast level scheme and reproducing the \begin{document}$I\!=\!10$\end{document} backbending. With the optimized condensation of neutron negative-parity pairs, we explain why the neutron negative-parity pairs have a large impact on the backbending behavior.
Correlation Between the Probability of Spin-zero Ground State and TBME in the Presence of Random Interactions
Jiajie SHEN
2020, 37(3): 523-529. doi: 10.11804/NuclPhysRev.37.2019CNPC15
Abstract:
The dominance of zero-spin ground state of even-even nuclei by two-body random ensemble(TBRE) is attributed to some of the two-body matrix elements(TBMEs). In this paper, we investigate the correlation between the probability of spin-zero ground state and TBMEs through enhance each TBME by changing the width of distribution and keep other TBMEs with standard gaussian distribution. We find that the probability of spin-zero ground state is insensitive to some TBMEs. Moreover, we further investigate the probability of spin-zero ground state through setting the centroid of TBME to realistic interaction, we find that the probability of spin-zero ground state is correlate with the centroid of TBME.
Collective Motion in 130Ba
Song GUO, Houbing ZHOU, C.M Petrache, Yunhua QIANG
2020, 37(3): 530-535. doi: 10.11804/NuclPhysRev.37.2019CNPC43
Abstract:
An in-beam \begin{document}${\rm{\gamma }}$\end{document} spectroscopic study, based on the XTU Tandem accelerator of the Laboratori Nazionali di Legnaro in Italy, has been performed to explore the collective motion in 130Ba. A significantly extended level scheme of 130Ba has been built in the present work. High-spin states of 130Ba were populated via the 122Sn(13C, 5n) reaction at a beam energy of 65 MeV. The \begin{document}${\rm{\gamma }}$\end{document} rays were detected by the GALILEO spectrometer, while the neutrons and charged particles were detected by the Neutron Wall array and the EUCLIDES silicon apparatus, respectively. A series of new rotational bands in 130Ba have been identified, among which there is a new structure populating to the previously known 9.4 ms isomer. With the help of previously reported intrinsic quadrupole moment and magnetic moment, we extracted precise value of the g factors of this isomer. According to the band structure analysis, the coexistence of prolate and oblate shapes has been observed in 130Ba, while the orientation of collective rotation can be either along or away from the principal axes. It is the first time to identify a tilted band in the A = 130 mass region. Theoretical analysis suggests that a new band can be interpreted as the wobbling motion built on two-quasiparticle configuration, which is the first wobbling band observed in an even-even nucleus.
α-decay Studies of the N=127 Isotones 219U and 216Ac
Mingming ZHANG, Zaiguo GAN, Zhiyuan ZHANG, Huabin YANG, Minghui HUANG, Long MA, Chunli YANG
2020, 37(3): 536-541. doi: 10.11804/NuclPhysRev.37.2019CNPC49
Abstract:
The light actinide nuclei 219U and 216Ac were produced in fusion-evaporation reaction using a 183W target and 40Ar beam. After recoiling from thin target, the fusion-evaporation residues were separated by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and transported into the focal plane detector systems, where their impantations and decays were measured. The method of searching for \begin{document}$ \alpha $\end{document}-decay chains was used to identify the nuclei. In this work, the known \begin{document}$ \alpha $\end{document} decay of 219U was measured with improved precision and the \begin{document}$ \alpha $\end{document}-particle energy of 9 763(15) keV and a half-life of 60(7) μs was determined. In addition, two new \begin{document}$ \alpha $\end{document}-decay lines at 9 246(17) keV and 8 975(17) keV were observed and assigned as the decays from the ground state of 219U to the (\begin{document}$5/2 ^{-} $\end{document}) and (\begin{document}$3/2 ^{-} $\end{document}) states of 215Th, respectively. The existence of an \begin{document}$ \alpha $\end{document}-decaying isomeric state in 216Ac was also confirmed.
Structural Investigation in 101Pd and Comparison in Its Vicinity
Rohilla Aman, Guangshun LI, Jianguo WANG, Minliang LIU, Xiaohong ZHOU, Song GUO, Yunhua QIANG, Bing DING, Dongsheng HOU, Shan HUANG
2020, 37(3): 542-547. doi: 10.11804/NuclPhysRev.37.2019CNPC17
Abstract:
The present work aims at the structural investigation of the \begin{document}$\gamma-$\end{document} levels in \begin{document}$\nu h_{11/2}$\end{document} band of 101Pd, and its comparison with the neighboring Pd-isotopes. Theoretical investigations performed in the vicinity of Pd-isotopes i.e., around \begin{document}$N\!=\!Z\!=\!50$\end{document} shell closures have described the systematic well, indicating an evolution of shape alongwith involvement of triaxiality. The deformation studies in the vicinity of Pd-isotopes around shell closures have predicted the shape change from small deformation to more deformed prolate shapes. The comparison of Total Routhian Surface (TRS) calculations performed in the present work have also suggested the inclusion of small amount of triaxiality as a function of increasing rotational frequency and neutron number, pointing towrads the \begin{document}$\gamma-$\end{document} softness present in the nuclei.
In-beam γ Spectroscopy of Neutron-rich 63,65,67Mn
Hongyang LU, Xiaoyu LIU, Bing DING, Zhong LIU, Doornenbal P., Obertelli A., Lenzi S. M., Walker P. M., Chung L. X., Linh B. D., Authelet G., Baba H., Calvet D., Château F., Corsi A., Delbart A., Gheller J.M., Gillibert A., Isobe T., Lapoux V., Matsushita M., Momiyama S., Motobayashi T., Niikura M., Nowacki F., Otsu H., Péron C., Peyaud A., Pollacco E. C., Roussé J. Y., Sakurai H., Sasano M., Shiga Y., Takeuchi S., Taniuchi R., Uesaka T., Wang H., Yoneda K.
2020, 37(3): 548-553. doi: 10.11804/NuclPhysRev.37.2019CNPC55
Abstract:
The excited states in 63,65,67Mn have been studied via in-beam \begin{document}$\gamma$\end{document}-ray spectroscopy following the knockout reaction of 68Fe by bombarding a liquid hydrogen target. Similar level schemes have been established for the three isotopes, and the level schemes consist of the 11/2, 9/2, 7/2 and 5/2g.s. states, which are connected by \begin{document}$\Delta I = 1$\end{document}. The level sequences of 65,67Mn show features of strongly coupled rotational band with \begin{document}$K^{\pi} = 5/2^{-}$\end{document} expected for the well deformed nuclei. Large-scale shell-model calculations using the modified LNPS (LNPSm) effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole (\begin{document}$4p-4h$\end{document}) neutron configurations and 1-particle-1-hole (\begin{document}$1p-1h$\end{document}) proton configurations for all the states. The experimental results show an enhancement of Urca neutrino cooling in the accreted neutron crust associated with \begin{document}$A = 63$\end{document} nuclei and rule out significant cooling from \begin{document}$A = 65,67$\end{document}.
Study of α Decay and Proton Radioactivity Half-lives Based on Improved Gamow-like Model
Junhao CHENG, Jiulong CHEN, Jungang DENG, Xiaohua LI
2020, 37(3): 554-562. doi: 10.11804/NuclPhysRev.37.2019CNPC08
Abstract:
In this paper, the Gamow-like model is improved by introducing centrifugal potential and electrostatic shielding, and it is used in the study of α decay and proton radioactivity. It is found that our calculations can well reproduce the experimental data. In addition, the modified Gamow-like model is used to predict the proton radioactivity half-lives of 116 proton-rich nuclei and α decay half-lives of seven even-even nuclei with \begin{document}$Z=120$\end{document}(\begin{document}$^{296-308}120$\end{document}) and some nuclei on their α decay chains. It will provide important theoretical references for the synthesis and identification of these new nuclides on large scientific devices in the future.
Spectral Structure Analysis of Nuclei 14C, 14,15N, and 14-18O Near Double Magic Nucleus 16O by Shell Model Calculations
Junji JIANG, Rui JIN, Hankui WANG
2020, 37(3): 563-568. doi: 10.11804/NuclPhysRev.37.2019CNPC54
Abstract:
According to three different interactions of YSOX, WBT and WBP, the spectral structure of nuclei 14C, 14,15N, and 14-18O near double magic nucleus 16O are analyzed by shell model calculations. The good effects have been found in spectral structure of these nuclei after reconsidering shell interaction. The large data analysis between these different shell model interactions and experiment also revealed the limitations of these existing interactions in this nuclei region, for example the large difference between theory and experiment, the reversed order of states and so on, which brings the further motivations of modifying shell model Hamiltonians.
Investigation of Kπ=2 Band in 248Cf
Yuan QIU, Yang SUN, Zaochun GAO
2020, 37(3): 569-573. doi: 10.11804/NuclPhysRev.37.2019CNPC59
Abstract:
An independent theoretical analysis is presented for the 2 band in 248Cf, which has been identified to spin \begin{document}$25{\hbar}$\end{document} and excitation energy \begin{document}$\geqslant$\end{document}4 MeV, implying the fission barrier persists at least up to that angular momentum and excitation for the configuration. The underlying physics for the experimentally observed band is discussed in terms of alignment properties and decay pattern. Different scenarios for assumptions about intrinsic configuration are assessed with transition rates analysis. It turns out that only by invoking a particle-phonon mixing picture can the decay characteristics of the pair of bands be well accounted for, i.e. quasiparticle nature forbids decay to ground-state band, non-axial octupole phonon shifts the signature partners in energy and diminishes mutual interaction. The coexisting normal and superconducting phases are tentatively attributed to weak neutron pairing in the proximity of 152 deformed shell gap.
Study on Halo Phenomenon in Exotic Nuclei by Complex Momentum Representation Method
Huaming DAI, Xueneng CAO, Quan LIU, Jianyou GUO
2020, 37(3): 574-579. doi: 10.11804/NuclPhysRev.37.2019CNPC07
Abstract(203) HTML (60) PDF (3410KB)(18)
Abstract:
The study of halo phenomenon gives us a new understanding of nuclear structure, in which the continuum, especially the resonance in the continuum, plays an important role. The complex momentum representation (CMR) method can not only describe the bound state, resonant state and continuous spectrum uniformly, but also describe the narrow and wide resonance well. In this paper, the CMR method is introduced for the study of nuclear resonance. The single particle energy of bound state and resonance state of 31Ne and 19C with deformation parameter β2 is given. The physical mechanism of halo formation in 19C and 31Ne and the reason of energy level inversion near the neutron number N=20 are analyzed. The halo phenomenon in nuclei heavier than 37Mg is predicted. The result of this prediction is helpful to find heavier halo nuclei in experiments. These studies show that the CMR method is suitable for describing not only stable nuclei, but also exotic nuclei with diffuse material distribution.
The Influence of Gogny Nucleon-nucleon Interaction Potentials of AMD on Ground State Properties of Nuclei
Jincheng WANG, Suyalatu ZHANG, Meirong HUANG, Wada Roy, Hua ZHENG, Dexin WANG, Na SONG, Xin TANG, Li LI
2020, 37(3): 580-585. doi: 10.11804/NuclPhysRev.37.2019CNPC11
Abstract:
In antisymmetrized molecular dynamics(AMD) model, the binding energies and root mean square (RMS) radii of 4He, 6Li, 12C, 20Ne, 40Ca and 60Ni in their own mean field were studied by three sets of Gogny interactions (g0, g0as and g0ass). The binding energies of isotopes with atomic numbers from 1 to 18 were studied systematically. Comparing with the experimental data, it is found that the result of g0 is the best. These investigations would provide clues to the study of the nuclear reaction mechanism such as fusion in low energy region and multi fragmentation in medium energy region by AMD.
Parallel Session Presentations-Nuclear reaction
Calculations of the 17O and 17F Spectra and 16O(p,p) Reaction Cross Sections in the Coupled-channel Gamow Shell Model
Michel Nicolas
2020, 37(3): 586-594. doi: 10.11804/NuclPhysRev.37.2019CNPC68
Abstract(114) HTML (57) PDF (3281KB)(22)
Abstract:
We apply the coupled-channel Gamow shell model to calculate the spectra of 17O and 17F, as well as 16O(p,p) elastic cross sections at low energies. It is shown that continuum coupling is necessary to account for the particle-emission width of the unbound eigenstates of 17O and 17F. The low-lying spectrum of 17O and 17F and 16O(p,p) excitations functions are in fair agreement with experimental data. Nevertheless, it is also shown that the use of a realistic nuclear Hamiltonian is needed to have an optimal reproduction of 16O(p,p) elastic cross sections in the low-energy region.
Energy Dependence of the Radial Sensitivity
Lei YANG, Chengjian LIN, Huiming JIA, Dongxi WANG, Feng YANG, Fupeng ZHONG, Shanhao ZHONG, Nanru MA, Peiwei WEN
2020, 37(3): 595-599. doi: 10.11804/NuclPhysRev.37.2019CNPC25
Abstract:
With the application of the notch technique, the radial sensitive regions for the tightly bound system 16O+208Pb, and weakly bound system 9Be+208Pb were investigated. It is the first time that the shape and resonant scattering can be identified from the sensitivity functions. Moreover, strong energy dependence of sensitive regions were found for both the tightly and stable weakly bound systems: in the above barrier region, the sensitive region varies around the strong absorption radius; while below the barrier, the behavior of sensitive region is close to that of the closest approach in the Coulomb field.
Prescission Particle Emission of Heavy Nuclei and the Probe of Postsaddle Friction
Ning WANG, Wei YE
2020, 37(3): 600-604. doi: 10.11804/NuclPhysRev.37.2019CNPC16
Abstract:
The stochastic Langevin model is applied to calculate the evolution of postsaddle emitted neutrons, protons and \begin{document}$ \alpha $\end{document} particles of heavy 240Am nuclei with the postsaddle friction strength(\begin{document}$ \beta $\end{document}). A significantly enhanced sensitivity of these particles to \begin{document}$ \beta $\end{document} has been observed at a high energy(\begin{document}$ E^* $\end{document}) and a large angular momentum(\begin{document}$ \ell $\end{document}). Moreover, the postsaddle emission as a function of \begin{document}$ \beta $\end{document} is compared under two contrasting initial conditions of (high \begin{document}$ E^* $\end{document}, low \begin{document}$ \ell $\end{document}) and (low \begin{document}$ E^* $\end{document}, high \begin{document}$ \ell $\end{document}) for the populated 240Am system. It is shown that for the former type of conditions, the influence of friction on particle evaporation is amplified and the sensitivity of light charged particles to friction is significantly increased. These results suggest that in experiment, to precisely probe the postsaddle friction through the measurement of particle multiplicity, in particular light charged-particle multiplicities, it is best to choose intermediate-energy heavy-ion collisions to produce highly excited heavy fissioning nuclei.
Application of Photonuclear Reaction to Evaluating Nuclear Polarizability in Muonic Atoms
Chen JI
2020, 37(3): 605-610. doi: 10.11804/NuclPhysRev.37.2019CNPC56
Abstract:
Recent measurements by CREMA Collaboration in Paul Scherrer Institute (Switzerland) determined the proton radius in Lamb shift spectroscopy of muonic hydrogen with a significantly improved precision. However, they discovered that this determination differs from the well-accepted CODATA value by 5.6 standard deviation. This discovery is named the “proton radius puzzle”, and attracted interests of many physicists. Inspired by this work, the CREMA Collaboration extended their experiments in muonic hydrogen to a series of light muonic atoms/ions, including \begin{document}$\mu^{2,3}$\end{document}H and \begin{document}$\mu^{3,4}$\end{document}He\begin{document}$^+$\end{document}. They planned to extract the radii of light nuclei (i.e., 2,3H,3,4He) from Lamb shift measurements in muonic atoms. Besides the spectroscopy precision, the accuracy of nuclear radii is limited by one theoretical input, i.e., nuclear polarizability. Nuclear polarizability originates from virtual excitation of the nucleus during the two-photon exchange process. This effect can make higher-order corrections to the muonic atom spectrum. Polarizability is strongly connected with the photonuclear reaction and the virtual Compton scattering. Therefore, its correction to the Lamb shift can be obtained by evaluating the sum rules of photoabsorption cross sections and forward virtual Compton amplitudes. Using ab initio methods, we calculated the nuclear polarizability effects in muonic atoms. By utilizing modern nuclear force models and the hyperspherical harmonic many-body approaches, we calculated a series of photonuclear sum rules, which are correlated with the nuclear polarizability. This theoretical work provides key input to the high-precision determination of nuclear radii in muonic atom spectroscopy.
Simulation Study of Lifetime Calculation Methods for Radioactive Nuclides
Qi ZENG, Ning WANG, Meng WANG, Yuhu ZHANG, Xiaolin TU, Xing XU, Ruijiu CHEN, Xiangcheng CHEN, Chaoyi FU, Junhao LIU, Hongfu LI, Min SI, Peng SHUAI, Mingze SUN, Yuanming XING, Xinliang YAN, Jiankun ZHAO, Xu ZHOU, Xiaohong ZHOU
2020, 37(3): 611-616. doi: 10.11804/NuclPhysRev.37.2019CNPC26
Abstract(126) HTML (39) PDF (3318KB)(16)
Abstract:
According to several common lifetime calculation methods of radioactive nuclides, the scope of applicable of the four calculation methods, which are named Method of Direct Fitting, Method of Logarithmic Time, Method of Maximum Likelihood and Method of Maximum likelihood when observation time windows is limited, are studied based on the simulation data. As the observation time window is limited or not, the applicable range of the lifetime calculation methods in different observation time windows and different counts are discussed. In simulation, fully stripped ion 94mRu44+ was selected as the target nuclide, the lifetime and error in different counts and different observation time windows are obtained, and the applicable range of the four methods is given. The experimental data of 94mRu44+ was obtained from the lifetime measurement experiment which is performed by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou. The simulation results are consistent with the experimental results within one error bar, thereby it is further verified the applicable range of the calculation method and the reliability of the simulation data. The simulation results provide theoretical basis and reference for the design of the future lifetime experiments.
Geant4 Simulations of Neutron Production Double Differential Yields in Light Charged Particle Induced Reaction
Xin ZHANG, Zhiqiang CHEN, Bingyan LIU, Rui HAN, Guoyu TIAN, Fudong SHI, Hui SUN
2020, 37(3): 617-620. doi: 10.11804/NuclPhysRev.37.2019CNPC48
Abstract:
The study of secondary neutrons produced by light charged particles induced reaction is of great significance to the design and optimization of accelerator shielding. The neutron double differential yields from 33 MeV-d, 65 MeV-3He and 65 MeV-4He bombarding thick carbon, copper and lead targets in the directions of \begin{document}$0^{\circ}$\end{document}, \begin{document}$15^{\circ}$\end{document}, \begin{document}$45^{\circ}$\end{document}, \begin{document}$75^{\circ}$\end{document}, \begin{document}$135^{\circ}$\end{document}, are calculated by using Geant4 code with INCL, BIC and BERT physics models, and compared with the experimental data. The results show that, for the 33 MeV d-induced reaction, the results from the INCL model basically reproduced the experimental data of carbon and copper targets, but overestimated the neutron yields corresponding to the direct process in lead target. The results from the BIC model and Bert models failed to reproduce the broad peak due to the stripping of the projectiles. For the 65 MeV 3He-induced reaction, the results from the three models could not reproduce the neutrons in the stripping process in the forward angles. The calculated ones with these three models agreed well with the experimental results in other angles. For the 65 MeV 4He-induced reactions, the calculation results of the INCL model are in good agreement with the experimental ones for carbon and copper targets, but underestimated the neutrons for lead target. The calculation results of the BIC model and BERT model underestimated the experimental data for carbon target and slightly overestimated the experimental ones for lead target in large angles.
Effect of Pairing Energy for Projectile Fragmentation Cross Sections
Jinxia CHENG, Donghai ZHANG, Junsheng LI
2020, 37(3): 621-625. doi: 10.11804/NuclPhysRev.37.2019CNPC21
Abstract:
The improved quantum molecular dynamics(ImQMD) model plus the GEMINI statistical decay model are used to analyze the odd-even effect of fragmentation cross sections for reactions 36Ar beams on C, Al, Cu, Pb targets at 400 AMeV. The result shows that the odd–even effect is appeared in the de-excitation process of primary fragments, and the pairing energy plays an important role. The odd–even effect of fragmentation cross sections disappears when the pairing energy is removed from the de-excitation process. The odd–even effect in neutron of fragmentation cross section is significantly.
Parallel Session Presentations-Nuclear astrophysics
Recent Progress of the Trojan Horse Method and Its Application
Chengbo LI, Qungang WEN
2020, 37(3): 626-635. doi: 10.11804/NuclPhysRev.37.2019CNPC28
Abstract:
The Trojan Horse Method(THM) is an important indirect method in experimental nuclear astrophysics. The S(E) factor of a two-body reaction in Gammow energy range related to astrophysics can be extracted from an appropriate three-body reaction measurement above the Coulomb barrier, under the quasi-free reaction condition. The method can overcome the difficulties caused by the Coulomb barrier suppression and the electron screening effect in direct measurement. While no extrapolation is needed, the method can also avoid the uncertainty in the extrapolation process. THM has a wide application in the experimental nuclear astrophysical study, low-energy fusion data measurement, neutron-induced reaction, electron screening effect and other important research fields. After a short introduction of the THM, this paper will focus on some of the most important experimental results in nuclear astrophysics measured by THM recently and the prospect of its future applications. The following key reactions will mainly be discussed: the indirect measurement of the key neutron source reaction \begin{document}$ ^{{\rm{13}}}{\rm{C(\alpha ,n}}{{\rm{)}}^{{\rm{16}}}}{\rm{O}}$\end{document} in the s-process of AGB stars, the indirect measurement of the nuclear reaction related to the fluorine abundance anomaly in AGB stars, as well as the recent hot spot, the indirect measurement results of the carbon burning reaction in medium or massive stars.
Active Target Time Projection Chamber (TPC) for Nuclear Astrophysics Experiments
Zhichao ZHANG, Ningtao ZHANG, Chengui LU, Tianlei PU, Jinlong ZHANG, Han CHEN, Limin DUAN, Binshui GAO, Kuoang LI, Yutian LI, Yi QIAN, Longhui RU, Xiaodong TANG, Xinyu WANG, Xiaodong XU, Hongyun ZHAO, Ziwei CAI, Binfei JI, Qite LI, Jinyan XU, Weiping LIN
2020, 37(3): 636-642. doi: 10.11804/NuclPhysRev.37.2019CNPC47
Abstract:
The fusion reaction of neutron-rich nuclei occurring in the neutron star crust is considered to be the important heating process in neutron stars and X-ray super burst. Limited by the intensity of radioactive beams and the complexity of reaction mechanism, experimental data so far are rare and can not constrain relevant theoretical model effectively. The time projection chamber (TPC) based on the active target technique works with the detection gas as the target, which can record all the tracks including the incident particle and charged particles from the reaction occurring in the detection gas. TPC has approximately 4\begin{document}$\pi$\end{document} solid angle acceptance and 3D track reconstruction capabilities, which can significantly improve detection efficiency, making TPC a powerful device to measure the low cross sections of fusion reactions. A 240-channels active target TPC has been developed. The test experiment of 16N+12C fusion measurement was carried out and validated the feasibility of measuring the fusion reaction cross section by active target TPC. In order to obtain more accurate reaction tracks to identify fusion events, a 1024-channels TPC was constructed and then commissioned by measuring the 12C+12C fusion reaction cross section at energies around coulomb barrier. The preliminary result is in good agreement with the existing experimental data.
Precision Measurement Proposal of Neutron Capture Reaction in Ge Isotopes for s-/r-process and Neutrino-less Double-beta Decay Within Its Relevant Energy Range
Zhendong AN, Chenchen GUO
2020, 37(3): 643-649. doi: 10.11804/NuclPhysRev.37.2019CNPC71
Abstract:
The reaction of 74,76Ge(n,\begin{document}$\gamma$\end{document}) is the key reaction of weak s-process in massive stars during He Core burning, and later during C Shell burning. And, in order to more accurately predict the neutron-induced internal background in the 76Ge based 0\begin{document}$\nu \beta \beta$\end{document} decay searches GERDA and MAJORANA, the neutron-capture cross section of 76Ge and 74Ge must be known. Because the present nuclear data library is limited by experimental condition and energy range, the precision of some nuclear data is low, some nuclear data are blank. The back streaming white neutron beam (Back-n) at China Spallation Neutron Source has very wide energy spectrum and excellent time structure. A high precision measurement of 74,76Ge neutron capture reaction will be carried out using C\begin{document}$_{6}$\end{document}D\begin{document}$_{6}$\end{document} detector from 10 keV\begin{document}$\thicksim 5$\end{document} MeV energy. In particular, the direct measurement of the 74,76Ge neutron capture reaction at 30 keV will be given, which is the most concerned with astrophysics. The work will provide key input of nuclear physics for understanding weak s-/r- process in massive stars. In year 2002, American National Research Council ranked “How were the heavy elements from iron to uranium made?” on the Discover magazine as one of the 11 Greatest Unanswered Questions of Physics of this century. The experiment is crucial to solve the key scientific questions. At the same time, accurate nuclear data of neutron-induced internal background is provided for GERDA, located at Italy’s Gran Sasso underground laboratory, the MAJORANA Demonstrator, at the US’s Sanford Underground Research Facility, and the \begin{document}$0\nu \beta \beta$\end{document} decay of CDEX collaboration in China Jinping Underground Laborotory (CJPL).
Parallel Session Presentations-Intermediate and high energy nuclear physics
Studies on Spin and Chiral Dynamics with Transport Simulations
Jun XU
2020, 37(3): 650-659. doi: 10.11804/NuclPhysRev.37.2019CNPC22
Abstract(1254) HTML (25) PDF (7953KB)(26)
Abstract:
Spin-related physics are hot topics in various research fields. Nucleons and quarks are both spin-half fermions. They are affected by the spin-orbit interaction as well as the magnetic field in non-central heavy-ion collisions, leading to interesting spin dynamics, especially the spin polarization perpendicular to the reaction plane. In relativistic heavy-ion collisions, the produced quarks can be approximately considered as massless particles due to the extremely high temperatures and high densities reached there, and the spin dynamics turns to the chiral dynamics in this case. Under the external electromagnetic field and vortical field, a series chiral anomaly effects may appear once there are asymmetries of electric charges and/or chirality charges. This manuscript reviews a series of studies on the spin and chiral dynamics based on transport simulations from our research group, including particle spin polarizations in intermediate-energy heavy-ion collisions and relativistic heavy-ion collisions, as well as chiral magnetic waves in an ideal system and in relativistic heavy-ion collisions.
Investigation of the Splitting in Elliptic Flow Between Protons and Anti-protons in ${^{{\bf{197}}}{\bf{Au}}}$+${^{{\bf{197}}}{\bf{Au}}}$ Collisions at ${\sqrt{{{s}}_{\bf{NN}}}\!=\!{\bf{5}}\thicksim{\bf{12}}~{\bf{GeV}}}$
Pengcheng LI, Yongjia WANG, Qingfeng LI, Hongfei ZHANG
2020, 37(3): 660-667. doi: 10.11804/NuclPhysRev.37.2019CNPC04
Abstract:
Utilizing ultra-relativistic quantum molecular dynamics (UrQMD) model, the elliptic flow \begin{document}$v_{2}$\end{document} for proton and anti-protons as well as the \begin{document}$v_{2}$\end{document} difference between proton and anti-protons from \begin{document}$^{197}{\rm{Au}}$\end{document}+\begin{document}$^{197}{\rm{Au}}$\end{document} collisions at center-of-mass energies \begin{document}$\sqrt{s^{}_{\rm{NN}}}=5\thicksim12$\end{document} GeV are investigated. By comparing the results from the UrQMD model with and without potential interactions, the \begin{document}$v_{2}$\end{document} of protons and anti-protons and their difference as a function of the transverse momentum \begin{document}$p_{\rm{t}}$\end{document}, incident energy \begin{document}$\sqrt{s^{}_{\rm{NN}}}$\end{document}, rapidity and centrality are analyzed. It is found that by including mean-field potentials, the transverse momentum, incident energy dependence of \begin{document}$v_{2}$\end{document} of protons and the \begin{document}$v_{2}$\end{document} difference in protons and anti-protons could be described well. And the \begin{document}$v_{2}$\end{document} difference is affected by the size of the windows (i.e. rapidity and centrality). These information are useful to understand the properties of nuclear matter at high density and thus exploring the structure of QCD (Quantum-ChromoDynamical) phase diagrams.
Collective Flow of Identified Particles in Heavy Ion Collisions at RHIC-STAR
Shusu SHI
2020, 37(3): 668-673. doi: 10.11804/NuclPhysRev.37.2019CNPC72
Abstract(185) HTML (64) PDF (5317KB)(14)
Abstract:
In this paper, we review the recent key results on anisotropic flow in heavy ion collisions at RHIC-STAR experiment. It mainly includes the results of elliptic flow of multi-strange and charm hadrons in top energy heavy ion collisions, and the results of elliptic and directed flow from RHIC Beam Energy Scan Program I. The results of 54.4 and 27 GeV are brand-new. We find the new results of directed flow follow the energy dependence trend; the Number of Constituent Quark scaling of elliptic flow indicates the partonic collectivity has been built-up in Au+Au collisions at 54.4 and 27 GeV. We also introduce the future plans of Beam Energy Scan experiments and the research focus of the anisotropic flow.
Chiral Crossover and Chiral Phase Transition Temperatures from Lattice QCD
Shengtai LI, Hengtong DING
2020, 37(3): 674-678. doi: 10.11804/NuclPhysRev.37.2019CNPC65
Abstract:
We review our recent studies on chiral crossover and chiral phase transition temperatures in this special issue. We will firstly present a lattice QCD based determination of the chiral crossover transition temperature at zero and nonzero baryon chemical potential \begin{document}$\mu_{\rm{B}}$\end{document} which is \begin{document}$T_{\rm{pc}}\!=\!(156.5\pm1.5)$\end{document} MeV. At nonzero temperature the curvatures of the chiral crossover transition line are \begin{document}$\kappa^{\rm{B}}_2$\end{document}=0.012(4) and \begin{document}$\kappa^{\rm{B}}_4$\end{document}=0.000(4) for the 2nd and 4th order of \begin{document}$\mu_{\rm{B}}/T$\end{document}. We will then present a first determination of chiral phase transition temperature in QCD with two degenerate, massless quarks and a physical strange quark. After thermodynamic, continuum and chiral extrapolations we find the chiral phase transition temperature \begin{document}$T_{\rm{c}}^0\!=\!132^{+3}_{-6}$\end{document} MeV.
Relativistic Kelvin Circulation Theorem for Ideal Magnetohydrodynamics
Jianfei WANG, Shi PU
2020, 37(3): 679-683. doi: 10.11804/NuclPhysRev.37.2019CNPC19
Abstract:
We have studied the relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. The relativistic Kelvin circulation theorem is a conservation equation for the called T-vorticity, We have briefly reviewed the ideal magnetohydrodynamics in relativistic heavy ion collisions. The highlight of this work is that we have obtained the general expression of relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. We have also applied the analytic solutions of ideal magnetohydrodynamics in Bjorken flow to check our results. Our main results can also be implemented to relativistic magnetohydrodynamics in relativistic heavy ion collisions.
Charm and Beauty Separation from Heavy Flavor Electron Measurements at RHIC
Fan SI, Xiaolong CHEN, Shenghui ZHANG, Yifei ZHANG
2020, 37(3): 684-689. doi: 10.11804/NuclPhysRev.37.2019CNPC13
Abstract(412) HTML (203) PDF (3437KB)(18)
Abstract:
Heavy quarks (charm and beauty), especially beauty, with expectedly different properties from light quarks are considered as ideal probes for the Quark-Gluon Plasma (QGP). However, there are few measurements on beauty hadrons or on their decay leptons. With the most recent measurements on charmed hadrons and heavy flavor decay electrons (HFE) at mid-rapidity in Au+Au collisions at \begin{document}$\sqrt{s_{\rm NN}}=200\;{\rm{GeV}}$\end{document} at RHIC, a data-driven method is developed to separate charm and beauty components from the HFE measurements. From charmed hadron measurements, electrons from charm decays via semileptonic decay simulations are obtained, with which the beauty component can be extracted from the HFE spectrum. As preliminary results, the \begin{document}$p^{}_{\rm T}$\end{document} spectra, \begin{document}$R_{\rm AA}$\end{document} and \begin{document}$v_2$\end{document} distributions of electrons from charm and from beauty decays (\begin{document}$R_{\rm AA}^{\rm c\rightarrow e}$\end{document} and \begin{document}$v_2^{\rm c\rightarrow e}$\end{document}, \begin{document}$R_{\rm AA}^{\rm b\rightarrow e}$\end{document} and \begin{document}$v_2^{\rm b\rightarrow e}$\end{document}) in minimum bias Au+Au collisions are presented, respectively. Less suppression of \begin{document}$R_{\rm AA}^{\rm b\rightarrow e}$\end{document} is observed compared with that of \begin{document}$R_{\rm AA}^{\rm c\rightarrow e}$\end{document} at moderate-to-high \begin{document}$p_{\rm T}$\end{document}, and \begin{document}$v_2^{\rm b\rightarrow e}$\end{document} shows smaller than \begin{document}$v_2^{\rm c\rightarrow e}$\end{document} at low-to-moderate \begin{document}$p_{\rm T}$\end{document}.
Application of the Dynamical Parton Model in Nucleon and Cold Nuclear Matter
Rong WANG
2020, 37(3): 690-697. doi: 10.11804/NuclPhysRev.37.2019CNPC33
Abstract:
This paper present a review on the dynamically generated sea quark and gluon distributions in the free nucleon and the cold nuclear medium. In the dynamical parton model, all the sea quarks and gluons come purely from the QCD fluctuations with DGLAP equations, where the small components of intrinsic sea quarks are neglected. The three valence quark distributions from maximum entropy method are taken as the nonperturbative input at \begin{document}$Q_0^2\sim 0.1$\end{document} GeV2. The saturated strong coupling at low \begin{document}$Q^2$\end{document} (\begin{document}$<1$\end{document} GeV2) is used in this work. Nucleon swelling and parton-parton recombination enhancement are considered for the nuclear matter. The dynamical parton distributions of both nucleon and cold nuclear matter are consistent with the experiments. Furthermore, we show a preliminary application of the nuclear parton distributions in the extraction of the parton energy loss penetrating in the cold nuclear medium.
Critical Exponents of the Chiral Phase Transition in the PNJL Model
Xueyan GAO, Weibo HE, Guoyun SHAO
2020, 37(3): 705-712. doi: 10.11804/NuclPhysRev.37.2019CNPC23
Abstract:
The critical exponents at the Critical end Point(CEP) and the spinodal boundaries are investigated in the Poyakov-Nambu--Jona-Lasinio(PNJL) model. The numerical results show that the four standard critical exponents, \begin{document}$\alpha, \beta, \gamma$\end{document} and \begin{document}$\delta$\end{document}, are consistent with Landau-Ginzburg theory in the mean-field approximation. The critical exponent \begin{document}$\eta ~(\approx2)$\end{document} correlated to kurtosis is larger than the critical exponent \begin{document}$\zeta~(\approx1)$\end{document} of skewness at the CEP, which indicates that the measurement of kurtosis is more sensitive than skewness if the critical region can be reached in heavy-ion collision. The calculation also shows that the critical exponent of skewness~(kurtosis) along the spinodal line has the same divergent strength as that at the CEP. Due to the violent fluctuations in the unstable and metastable phases and the divergence of skewness and kurtosis at the spinodal boundaries, the signals to identify the first-order transition in the future experiments will be disturbed to a certain degree. Some deviations from the prediction of standard first-order transition may be found in observation.
Roberge-Weiss Transition in the Polyakov-loop Extended Quark-meson Model
Qiyue ZHANG, Zhao ZHANG
2020, 37(3): 713-719. doi: 10.11804/NuclPhysRev.37.2019CNPC35
Abstract(203) HTML (13) PDF (3395KB)(13)
Abstract:
\begin{document}${\mathbb{Z}}_3$\end{document}-QCD is a QCD-like theory with strict center symmetry. We use the Polyakov-loop extended quark meson model (PQM) as a low-energy effective theory of \begin{document}${\mathbb{Z}}_3$\end{document}-QCD to study the RW transitions in different center symmetry breaking patterns. The flavor-dependent imaginary chemical potentials, namely \begin{document}$(\mu_{\rm{u}},\,\mu_{\rm{d}},\,\mu_{\rm{s}})= {\rm{i}}T(\theta-2C\pi/3,\theta,\theta+2C\pi/3)$\end{document} are adopted, which guarantees the RW periodicity. The traditional and quark improved Polyakov-loop potentials are used, respectively. For \begin{document}$N_{\rm{f}}\!=\!3$\end{document} with \begin{document}$C\!\ne\!1$\end{document}, the RW transition occurs at \begin{document}$\theta\!=\!\pi/3$\end{document} (mod \begin{document}$2\pi/3$\end{document}), which gets stronger when \begin{document}$C$\end{document} declines from one to zero. When \begin{document}$C\!=\!1$\end{document}, the RW transition happens at \begin{document}$\theta\!=\!2\pi/3$\end{document} (mod \begin{document}$2\pi/3$\end{document}) for \begin{document}$N_{\rm{f}}\!=\!2+1$\end{document}, but \begin{document}$\theta\!=\!\pi/3$\end{document} (mod \begin{document}$2\pi/3$\end{document}) for \begin{document}$N_{\rm{f}}\!=\!1+2$\end{document}. We find that all RW transition endpoints are triple points when \begin{document}$C\!=\!1$\end{document}. We confirm that the RW transition becomes weaker and the deconfinement temperature gets lower when taking into account the quark back-reaction effect. However, the modification of the gluon sector due to the quark effect does not change the main conclusions mentioned above.
Deep Learning for Nuclear Physics
Longgang PANG, Kai ZHOU, Xinnian WANG
2020, 37(3): 720-726. doi: 10.11804/NuclPhysRev.37.2019CNPC41
Abstract(343) HTML (153) PDF (4083KB)(74)
Abstract:
Deep learning is the state-of-the-art pattern recognition method. It is expected to help scientists to discover most relevant features from big amount of complex data. Different categories of deep learning, the best deep neural network architectures for different data structures, the interpretability of black-box models and the uncertainties of model predictions are reviewed in this article. The applications of deep learning in nuclear equation of state, nuclear structure, mass, decay and fissions are also introduced. In the end, a simple neural network is trained to predict the mass of nucleus. We found that the artificial neural network trained on experimental data has low prediction error for experimental data that are held back. Trained with experimental data, the network predictions for light neutron-rich nuclei deviate from Macro-Micro Liquid model, which indicate that there might be new physics missing in the theoretical model and more data are needed to verify this.
Intermediate and high energy nuclear physics
τ Lepton Decays and Applications
Lianrong DAI
2020, 37(3): 698-704. doi: 10.11804/NuclPhysRev.37.2019CNPC24
Abstract:
A novel algebraic approach recently proposed is presented in this paper for investigating the \begin{document}$\tau$\end{document} lepton decay process. In this approach, we use the basic weak interaction and angular momentum algebra and finally obtain analytical decay amplitudes, finding that this formalism can relate the different decay processes and also lead to a different interpretation of the important role played by \begin{document}$G$\end{document}-parity in these decays. Then we apply this formalism to explore some meaningful and interesting applications on \begin{document}$\tau$\end{document} lepton decays, including the polarization amplitudes and tests on the nature of scalar resonances or axial-vector resonances. The results show that one magnitude is very sensitive to the \begin{document}$\alpha$\end{document} parameter and useful to test different models Beyond the Standard Model. And very importantly, we firstly open up a new direction in the \begin{document}$\tau$\end{document} decays to test the nature of resonances which were obtained as dynamically generated from the pseudoscalar-pseudoscalar or vector-pseudoscalar interactions. In these \begin{document}$\tau$\end{document} decays we make predictions for invariant mass distribution and the final branching ratios, the results show that these ratios are within measurable ranges on related experiments in the possible future large research facility of the Super Tau-Charm Facility of China.
Parallel Session Presentations-Detector, electronics and application technology
Detector Design of the Polarized Electron Ion Collider in China
Kanghui QI, Yutie LIANG, Rong WANG, Yaping XIE, Zhi YANG, Yuxiang ZHAO
2020, 37(3): 727-733. doi: 10.11804/NuclPhysRev.37.2019CNPC37
Abstract(155) HTML (64) PDF (4810KB)(21)
Abstract:
Nucleon, the main building block to the visible matter in the universe, is an ideal laboratory to study the strong interaction. In the experimental study of nucleon structure, Electron Ion Collider(EIC) plays important role. EIC is a super electron-microscope being able to take clear image of the inner structure of the nucleon, and hence is an effective tool to gain insights into the fundamental constituents of matter, e.g., especially the structures of the nucleon and nuclei. The Electron-ion collider in China(EicC) project is proposed based on the HIAF facility by promoting its ion beam to an energy around 15~25 GeV, which is then enforced to collide with an electron beam of 3~5 GeV. Both beams are polarized and their center-of-mass energy is 10~20 GeV. The main physics motivations include the precision measurements to the nucleon internal structure in the sea-quark region, and the promotion of our understanding of the origin of proton spin and mass, the study of exotic states, etc. In the paper, a fast simulation package based on parametrisation is developed for EicC. With the simulation package, one EicC detector conceptual design is proposed based on the virous physics simulations.
Inner Tracking System Upgrade for the ALICE Experiment
Biao ZHANG, Li-ang ZHANG, Wenjing DENG, Jun LIU, Wenjing ZHANG, Donghai LIU, Yalei TAN, Yaping WANG, Xiangming SUN, Zhongbao YIN, Daicui ZHOU, Guangming HUANG, Nu XU
2020, 37(3): 734-741. doi: 10.11804/NuclPhysRev.37.2019CNPC51
Abstract:
A Large Ion Collider Experiment(ALICE) at the Large Hadron Collider(LHC) at CERN will undergo a major upgrade during the 2nd LHC Long Shutdown(LS2) scheduled in 2019~2021 that will allow to study in detail of strong interaction matter Quark-Gluon Plasma(QGP) properties. To collecting more Pb-Pb events during the Run 3 and Run 4, the replacement of the existing Inner Tracking System(ITS) with a completely new ultra-light high resolution detector based on Monolithic Active Pixel Sensors(MAPS) technique is one of the cornerstones within this upgrade program. The new ITS will consist of seven detection layers: 3 inner layers, 2 middle layers and 2 outer layers. The upgraded ITS will be realized using more than twenty-four thousand pixel chips (called ALPIDE) covering a total active surface of about ten square meters. The thickness of ALPIDE is 50 μm, also with a pixel pitch of 27 μm × 29 μm. The main features of the ALPIDE are of low power consumption, high resolution and high speed readout. ITS2 will enable the ALICE detector to have excellent detection efficiency and impact parameter resolution when measuring extremely low transverse momentum particles, and also make the ALICE detector suitable for LHC high luminosity environment. At present, the production and test of the detector module of ITS2 project have been completed, and the integration of 7-layer barrel been completed at CERN clean room, and the on-surface commissioning has been completed in the end of 2020. The installation plan of ITS2 at the ALICE detector has been started in Jan. 2021, and is scheduled to be finished in end of May 2021. This talk will focus on the design and the physics performance of the new ITS, as well as the advanced techniques adopted in detector assembly and integration will be introduced. The status and commissioning of the ITS upgrade project will be reported.
Data Analysis Framework for Radioactive Ion Beam Experiments at the External Target Facility of HIRFL-CSR
Yazhou SUN, Yixuan ZHAO, Shuya JIN, Shitao WANG, Zhiyu SUN, Xueheng ZHANG, Duo YAN, Shuwen TANG, Peng MA, Yuhong YU, Ke YUE, Limin DUAN, Herun YANG, Chengui LU, Fang FANG, Hong SU
2020, 37(3): 742-748. doi: 10.11804/NuclPhysRev.37.2019CNPC27
Abstract:
ANAETF, a large data analysis framework for the External Target Facility (ETF) of HIRFL-CSR, has been developed and successfully used for data analysis in radioactive ion beam experiments. This paper covers the flow of data processing in the program, the general tracking algorithm for the drift chambers, the particle identification (PID) approach, and the techniques for extraction of reaction cross sections. The program achieves total detecting efficiencies of around ~90% and gives clear PID spectrum for carbon and beryllium fragments produced from the reaction of 240 MeV/u 12C secondary beams on a carbon target. The obtained cross sections are consistent with the previously reported experimental results.
Time Performance Study of Plastic Scintillator Detector with SiPM Readouts
Bingqian ZHOU, Xueheng ZHANG, Fang FANG, Duo YAN, Shuweng TANG, Yuhong YU, Shitao WANG, Yongjie ZHANG, Xiangman LIU, Yixuan ZHAO, Shuya JIN, Zhong LIU, Zhiyu SUN
2020, 37(3): 749-756. doi: 10.11804/NuclPhysRev.37.2019CNPC53
Abstract(326) HTML (110) PDF (3176KB)(25)
Abstract:
In this paper the time performance of a plastic scintillator detector with an area of 10 cm×10 cm and read out by multiple silicon photomultipliers (SiPMs) at both ends was studied. The results tested with a 239Pu source are shown as: (1) the time resolutions became better gradually with the increase of the quantities of SiPMs connected in series; (2) when the number of 12 SiPMs was fixed, the time resolutions got worse as the number of parallel branches were increased; (3) the detector time resolutions can be effectively improved by using a fast-time plastic scintillator and adding its thickness; (4) to improve the positional uniformity of the time resolution, the scintillator with larger dimensions than beam spots should be used; (5) a resolution less than 131 ps was achieved with a 0.1 cm thickness EJ232 scintillator detector read out on each side by 12 SiPMs conncted in series. This study has importance significance for the upgrading of the start detector at RIBLL2.
Study of the ${\gamma} $-Ray Detector of Dual-ended Readout Based on SiPM
Xiangman LIU, Shuwen TANG, Wufeng LIU, Zhiyu SUN, Yuhong YU, Wei WANG, Ruofu CHEN, Junling CHEN, Yongjie ZHANG, Fang FANG, Duo YAN, Shitao WANG, Xueheng ZHANG, Jianwei LU, Bingqian ZHOU
2020, 37(3): 757-764. doi: 10.11804/NuclPhysRev.37.2019CNPC03
Abstract(619) HTML (484) PDF (3457KB)(50)
Abstract:
At present, study of the novel Compton telescope with high sensitivity has great scientific significance. The calorimeter, as one of the important components of the Compton telescope, is required to have excellent energy resolution and position resolution. For this purpose, a CsI(Tl) \begin{document}$\gamma $\end{document}-ray detector of dual-ended readout based on silicon photomultipliers (SiPM) was designed as the basic detection unit of the calorimeter for the Compton telescope. Different wrapping materials (Teflon, Tyvek and ESR) and different crystal sizes (5 mm×5 mm×60 mm, 5 mm×5 mm×80 mm and 5 mm×5 mm×100 mm) were used to construct the detectors, and the detectors were tested with a 137Cs source. The influence of the wrapping materials was not significant to the energy resolution but quite pronounced to the light attenuation length and position resolution. Besides, the light attenuation length and position resolution showed strong correlation, i.e. the shorter light attenuation length corresponding to the better the position resolution; In addition, for the three detectors using different sizes of the crystals, they did not show significant differences in performance. Eventually, the CsI(Tl) crystal detector with the size of 5 mm×5 mm×80 mm and the wrapped with ESR was determined to construct the detector satisfied with the requirements of the calorimeter for the novel Compton telescope. The energy resolution can reach 5.2% and the position resolution is about 5.2 mm.
Experimental Research on Transmission Performance of GEM Readout Detector in CEE-TPC
Xianglun WEI, Chengui LU, Junwei ZHANG, Peng MA, Herun YANG, Tianli QIU, Meng LI, Rongjiang HU, Limin DUAN
2020, 37(3): 765-770. doi: 10.11804/NuclPhysRev.37.2019CNPC46
Abstract:
The Gas Electron Multiplier (GEM) has attracted wide attention due to its better position resolution and isotropic two-dimensional structure, GEM is also planned to be used as the TPC readout detector in CSR External-target Experiment (CEE) under construction. The transmission characteristics of GEM under different electric field conditions have great influence on the effective gain and energy resolution of the detector. In this paper the effects of the electric field in the drift region and the induction region on the transmission characteristics of the detector are performed on single GEM, and the effects of voltage distribution and electric field in induction region on the transmission characteristics of double-layer GEM detector were studied. The results show that in single and multi-layer GEM detectors, electric fields in the different region affect the transmission characteristics of the detector mainly by changing the electron transmittance and changing the avalanche field intensity and distribution of GEM, which will affect the effective gain and energy resolution of the detector finally. The above experimental results indicate that GEM detector is a good candidate for CEE-TPC readout detector and they also provide a reference for the selection of the working point of multi-layer GEM in TPC.
Study of Neutron Shield and Absorber for Gamma Total Absorption Facility
Qiwei ZHANG, Guangyuan LUAN, Guozhu HE, Pinjin CHEN, Xichao RUAN, Xinghua ZHU
2020, 37(3): 771-776. doi: 10.11804/NuclPhysRev.37.2019CNPC30
Abstract:
The first gamma total absorption facility (GTAF) in China has been constructed in China Institute of Atomic Energy, which will be used to accurately measure the neutron capture cross section by prompt gamma method. A neutron source is established by 7Li(p, n)7Be reaction using pulsed proton beams generated by HI-13 tandem accelerator of CIAE. In order to effectively reduce the scattering neutron background produced by surrounding materials and detectors, and restrain the shape of neutron beam, neutron shield with boron-containing polyethylene (5% of B4C) coated with 5 cm lead and collimator of parallel hole are designed by MCNP program. The design makes spot of neutron beam flat and uniform, the diameter is about 2 cm, the flux of neutron outside the beam spot is reduced by 5 orders of magnitude, and the flux of gamma is reduced by 3 orders of magnitude. At the same time, neutron absorber (the outer radius is 10 cm, the thickness is 7 cm) is designed, which is used to absorb the scattered neutrons produced by the sample to be measured. The simulation results of MCNP and GEANT4 show that the boron containing polyethylene (10B4C mass fraction is 10%) is selected as the processing material of neutron absorber, in which the rate of neutron absorption reaches 80%, and the threshold of sum energy is set to 1 MeV, which meets the requirement of on-line experiment about the measurement of neutron capture cross section.
Background Shielding Design for TMSR Photoneutron Source
Xiaohe WANG, Jifeng HU, Longxiang LIU, Hongwei WANG, Xiangzhou CAI, Jingen CHEN, Naxiu WANG, Bing JIANG, Zian GUO, Jianlong HAN
2020, 37(3): 777-783. doi: 10.11804/NuclPhysRev.37.2019CNPC38
Abstract:
In order to meet the nuclear data requirement of Thorium Molten Salt Reactor (TMSR), a compact photoneutron source (PNS) driven by a 15 MeV electron LINAC was designed and built up by Shanghai Institute of Applied Physics. All devices including the LINAC, the neutron production target and the detector systems were all arranged in a shared hall, causing high backgrounds of neutron and γ-ray. The existing shields could not meet the requirements of low neutron background for the measurement in the thermal neutron energy regions. Therefore, more shields are needed to further reduce the neutron and γ-ray backgrounds. According to the analysis of neutron background source terms and the simulation of shielding effects of lead, concrete and boron polyethylene, the new local shields was designed. The MCNP5 simulation results show that, the new local shields can reduce the thermal neutron background by three orders of magnitude and the γ-ray background by two orders of magnitude. The experimental results with the new local shields show that, the ratio of effective thermal neutron to background thermal neutron is up to 100:1, which is of great significance for launching the foreseen physics program in the thermal neutron energy regions.
Development the Miniaturized AMS System and Its Analysis Technique
Ming HE, Yiwen BAO, Shengyong SU, Qubo YOU, Kangning LI, Qingzhang ZHAO, Yijun PANG, Pan HU, Wenhui ZHANG, Jie GONG, Hongyu HE, Yueming HU
2020, 37(3): 784-790. doi: 10.11804/NuclPhysRev.37.2019CNPC01
Abstract(133) HTML (64) PDF (3711KB)(10)
Abstract:
Accelerator mass spectrometry(AMS) is the most sensitive analytical technique for measuring long-lived radionuclides, which is widely used in the fields of environment, geology, archaeology and physics. In recent years, the miniaturization of AMS device has been greatly developed in the world. In order to develop miniaturized AMS devices and their analysis technology, China institute of atomic energy has independently developed a single-stage AMS device with an acceleration voltage of 0.2 MV and a tandem AMS device with an terminal voltage of 0.3 MV, respectively. Based on the single-stage AMS device, the high efficiency transport technique and background eliminating method have been developed for 14C measurement, and realized the high sensitivity measurement of 14C. The measurement sensitivity reaches 14C/12C (atomic number ratio)=2×10–15. Using the 0.3 MV tandem AMS device, the gas stripping conditions, background eliminating and detection methods of 129I at low ion energy were systematically studied, and the high efficient transmission and high sensitive measurement methods of 129I were established, the sensitivity is 129I/127I=1×10–14. This is the first time to develop miniaturized AMS devices in China, which lays the foundation for the localization of AMS.
Raw Material Characteristics of the White Porcelain from Huangye Kiln by Multivariable Statistics Analysis
Weijuan ZHAO, Tian GAO, Dongyan WANG, Xinmin SUN, Musen GUO, Bin ZHANG
2020, 37(3): 791-796. doi: 10.11804/NuclPhysRev.37.2019CNPC76
Abstract:
Huangye kiln has rich culture connotation. It originated in the Sui Dynasty, flourished in the mid Tang Dynasty and declined in the late Tang Dynasty. To discuss whether the raw material sources and glaze formulations of the white porcelain from Huangye kiln are the same in different periods, 80 white porcelain samples from Huangye kiln in four periods, namely the Sui Dynasty, the early Tang Dynasty, the middle Tang Dynasty, and the late Tang Dynasty, were selected. The content of 9 chemical components (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, and Fe2O3) of the body and glaze of each sample was measured by proton induced X-ray emission (PIXE). Then the data were analyzed with Fisher discriminant analysis. The types of white porcelain glazes of Huangye kiln were classified by calculating the b value of the glazes. The results show that the bodies of the white porcelain from Huangye kiln in four periods may have been made of local raw materials taken from the same or nearby locations, that the glaze formulations in four periods are similar, and that the glaze formulation in the fourth period is the most stable and the most similar to that in the second period, but obviously different from that in the first period. They also show that most of the glazes of the white porcelain from Huangye kiln belong to the category of calcium glaze, and that a small quantity of glazes belongs to the categories of calcium-alkali glaze and alkali-calcium glaze.
High-fidelity Neutronics and Thermal Hydraulics Coupling Method and Its Application
Zhouyu LIU, Liangzhi CAO
2020, 37(3): 797-803. doi: 10.11804/NuclPhysRev.37.2019CNPC73
Abstract(878) HTML (22) PDF (10468KB)(26)
Abstract:
The reactor core phenomena can be simulated and predicted with the high-fidelity neutronics coupled with thermal-hydraulics analysis, and the economic and safety of nuclear reactor could be further improved by using this new simulation tools. This work studied the methods of precise geometry modeling, accurate neutronics calculations and coupling with the pin-by-pin subchannel thermal-hydraulics, and a new high-fidelity neutronics and thermal hydraulics coupling code ENCP-X/CTF are developed. Some sensitivity analysis of the fuel rod heat conductance model, gap conductance model to the coupling results is performed, and the coupling system is applied for the large pressurized-water reactors. The results demonstrate that not only accurate macro parameters could be obtained, but also the detailed pin-level power distribution and temperature distribution could be analyzed.
Physical Properties of ZnS Thin Films Prepared by Low-temperature Sulfidation
Guang YANG, Rengang ZHANG, Shuzhen CHEN, Jinlin KE, Xingzhong CAO, Peng ZHANG, Runsheng YU, Baoyi WANG
2020, 37(3): 804-808. doi: 10.11804/NuclPhysRev.37.2019CNPC02
Abstract:
In the article, Zn thin films were deposited on the glass substrates at room temperature by magnetron sputtering from a zinc target. And ZnS thin films were prepared by annealing Zn thin films in sulfur vapor and Ar gas at 200 and 400 ℃. The microstructure defects, crystallizations, surface morphology and optical properties of the samples were analyzed by PAT(positron annihilation technique), XRD(X-ray diffraction), SEM(scanning electron microscopy) and UV-VIS spectrophotometer. The resultant ZnS thin films exhibited a high optical transmittance of about 80% in the visible region. With the increase of sulfidation time, the band-gap value was increased from 3.55 to 3.57 eV, and the S/Zn atomic ratio was enhanced from 0.54 to 0.89, implying an obvious improvement of ZnS film quality. This demonstrated that the excess-sulfur problem in the ZnS films was well solved compared with those samples prepared by sulfidation in the vacuum-sealed quartz-glass ampoules. Besides, the structural defects of the thin films before and after sulfidation were investigated by positron annihilation Doppler broadening measurements. It was found that the S parameter of the samples after sulfidaton was greater than that before sulfidation, implying the higher structural defect concentration for the former.