Subjects: Physics >> Nuclear Physics submitted time 2023-06-12 Cooperative journals: 《核技术》
Abstract： Exploring the quantum chromodynamics (QCD) phase diagram at finite bayron density regime through the beam energy scan (BES) program at the relativistic heavy-ion collider (RHIC) is one of the key frontiers in high energy nuclear physics. The high precision data anticipated from the second phase of the BES program would potentially enable the discovery of the conjectured QCD critical point, a landmark point on the phase diagram. In this paper, the progress made by the beam energy scan theory (BEST) collaboration, which was formed with the goal of providing a theoretical framework for analyzing data from BESII, is reviewed. In addition, the challenge of investigating the QCD phase diagram with future facilities is discussed.
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2023-11-09
Abstract： The fluorescence screen system is used to measure beam transverse profile in the accelerator. In order to further improve the measurement accuracy of the system, this paper proposes a method, filling the orientation lines of fluorescence screen with a simplified Fast Matching Method (FMM), so that the filled fluorescence screen images can reflect the beam profile information more truly. Firstly, the study uses Matlab to generate the simulated fluorescence screen images, and comparative analysis the beam profile parameters of the analog image before and after algorithm processing. The simulation results show that the Structural Similarity Index Measure (SSIM) of the processed simulated image is closer to 1, and the Mean Square Error (MSE) is smaller. Finally, the fluorescence screen images collected by the medical Heavy Ion Medical Machine (HIMM) were used for verification. After processing the fluorescence screen images collected by HIMM, the profile measurement results are close to the evaluation value. The results of this study provide a basis for the FPGA algorithm acceleration of the subsequent beam transverse profile parameter algorithm.
Subjects: Physics >> Nuclear Physics submitted time 2024-03-19
Abstract： In heavy ion collisions (HICs), the production of light particles plays an important role in extracting information about the equation of state (EoS) of nuclear matter. Based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the effect of the sequential decay on the collective flows and the nuclear stopping power of light particles in Au+Au collisions at intermediate energies were investigated, with the statistical decay model GEMINI++ is used to process the secondary decay of the primary fragments. It is found that due to the memory effect and the daughter nuclei produced by decay inherent part of the dynamic information of the parent nucleus, the experimental data can be better described by considering the sequential decay. And the influence of the sequential decay on the observables weakens with the increase of the collision energy. The results highlight that the sequential decay and the production of light particles in HICs have an obvious effect on the observables which sensitive to the EoS, and these effects should be considered when adopting these observables to extract the information of the EoS.
Subjects: Physics >> Nuclear Physics submitted time 2023-09-04 Cooperative journals: 《核技术》
Abstract： BackgroundMachine learning, which has been widely applied to scientific research in recent years, can be used to investigate the inherent correlations within a large number of complex data. PurposeWe evaluate the performances of two types of machine-learning algorithms for correcting nuclear mass models, reconstructing the impact parameter in heavy-ion collisions, and extracting the symmetry energy slope parameter. We also discuss the extrapolation and generalization ability of the machine-learning models. MethodFor correcting the nuclear mass models, 10 characteristic quantities are fed into the LightGBM to mimic the residual between the experimental and the theoretical binding energies. For impact parameter or symmetry energy, two types of observables constructed based on the particle information simulated by using the UrQMD transport model for setting up the different impact parameters or symmetry energy slope parameters are used as inputs to a conventional neural network and the LightGBM to extract the original information. ResultAnalysis of these nuclear physics problems reveals the potential applicability of machine-learning methods. ConclusionsMachine-learning methods can be used to investigate new physical problems, thereby promoting the development of both theory and experiment.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-04-10
LIN Shen
SONG Luyang
SU Jun
CHEN Xin
SHEN Zhilin
ZHANG Hao
SHENG Yaode
ZHANG Liyong
HE Jianjun
CHEN Size
SHEN Yangping
JIN Shilun
LU Fei
XIAO Dan
ZHANG Yong
NAN Wei
JIANG Yuchen
ZHANG Yuqiang
ZHANG Yang
TIAN Junwen
Abstract： In thermonuclear reactions of nuclear astrophysical interest, some can produce short-lived products that emit positrons. The positrons emitted by these products will annihilate with electrons in the target and then produce a pair of 511 keV γ-rays, which can be used to determine the reaction yield and calculate the cross-section as well as the astrophysical S-factor. Recently, it has been found that the spatial coincidence measurements can be performed basing on the opposite direction of the 511 keV-511 keV γ-ray pair, which can reduce the natural background and enables the in situ measurement of the reaction yield using activity method. In this paper, based on the recently developed large modular BGO detector array LAMBDA-II, this method has been investigated and validated in the ground laboratory, which provides good basis for further application of this method in the nuclear astrophysical investigations in the future.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-01
Hua Leiming
Lu Fei
Su Jun
Shen Yangping
Jin Shilun
Yang Guochun
Li Zhihong
Guo Bing
Liu Longxiang
Cao Xiguang
Abstract： The 𝛽-Oslo experimental method provides an important investigative tool for examining the properties of radioactive nuclides in highly excited states and exploring the nucleosynthesis process for elements ranging from iron to uranium. This paper introduces a novel data processing technique designed to eliminate the impact of 𝛽-decay electrons on the detection of nuclear 𝛾 de-excitation within 𝛽-Oslo experiments, accurately unfolding the observed 𝛾-ray spectra. Utilizing a comprehensive detector response function matrix for 𝛾 rays and decay electrons, this method combines column-pivotal elimination and iterative step-by-step inverse solution approaches to determine the true incident 𝛾 spectrum. The reliability and validity of the proposed method have been substantiated through extensive simulations and inverse calculations.
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