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Modification on theory of sink strength an Object Kinetic Monte Carlo study

Hou JieSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Sink strength is a fundamental quantity in modeling the microstructure evolution of irradiated materials by the mean-field approaches. The analytical expressions for different sinks have been extensively studied. The Object Kinetic Monte Carlo (OKMC) simulations were subsequently performed to corroborate the expressions and to guide the development of analytical theories. Although a general agreement was found between the theory and simulation, there are still some discrepancies in the case of the small spherical sinks and the dislocation lines. In this work, OKMC simulations were performed to study the sink strength of spherical sinks and dislocation lines. Our results revealed the origins of discrepancies between the theory and simulation for small sinks, high volume fraction sinks and periodically distributed dislocation lines. The theoretical corrections were also proposed accordingly. These corrections can extend the capabilities of mean-field approaches to properly reproduce the defect evolution of irradiated materials, and provide a better insight into the experimental phenomena, such as the defect cluster nucleation, the irradiation-induced swelling and the blistering. |

Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

软物质物理已成为物理学发展迅速的重要前沿学科。描述软物质复杂非平衡态动力学及其运动规律是理解其宏观性质的关键。内耗与力学谱作为材料缺陷与力学性质研究的重要实验技术，它能够很灵敏探测和研究材料中发生的复杂相变和弛豫动力学过程。文章结合作者近年来的典型工作，介绍了内耗技术在软物质研究中的一些应用，阐述了内耗手段发挥的独特作用。随着内耗测试新方法、新技术和内耗新理论的不断出现和完善，相信未来内耗技术在材料科学和凝聚态物理研究领域将起到越来越重要的作用。 |

Simulation of positron backscattering on Al, Cu, Ag and Au targets using GEANT4 code

Xin Lai; Xiaopan Jiang; Xingzhong Cao; Xi Zhang; Zhiming Zhang; Xuexiang Cao; Gang Xiang; Baoyi Wang; Long WeiSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

In this paper, backscattering of 3-50 keV positrons on Al, Cu, Ag and Au metallic targets has been systematically investigated using GEANT4 code. The dependence of positron backscattering coefficients on atomic number Z, target thickness, incident energy and angles has been discussed comprehensively. Besides, positron backscattering spectra for those metallic targets at different discrete scattering angles were also studied to provide theoretical basis of the most appropriate scattering angle selected for simulation parameters and specified applied measurement techniques. The impact of atomic number Z of targets on positron backscattering spectra was investigated as well. Simulation results are in reasonable agreement with previous experiment data and theoretical work. |

Discussion on upper limit of the precision for τ mass measurement

X. H. MoSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

τ lepton is one of three chareged leptons in nature, the measurements of its mass have been performed since its discovery. The present relative accuracy is already at the level of 10−4; more factors are still being studied in order to increase the accuracy. However, the available techniques for analysis and expectable luminosity from e+e− collider indicate that the precision upper limit of τ mass is almost reached, which means that brand new approaches should be looked for if the great improvement is yearned for. |

On uncertainty of the beam energy measurement in e+e− collision using Compton Backscattering.

X. H. MoSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The beam energy is measured in e+e- collision by using Compton Backscattering. The uncertainty of this measurement process is studied by virtue of analytical formulas, and the special effects of variant energy spread and energy drift on the systematic uncertainty estimation are also studied with Monte Carlo sampling technique. These quantitative conclusions are especially important for understanding the uncertainty of beam energy measurement system. |

On two cryogenic systems of high purity germanium detector

Zhang Jian-Yong; Cai Xiao; MO Xiao-HuSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Two cryogenic systems of high purity germanium detector, liquid nitrogen and mechanical coolers, are expound, together with explanations of merits and demerits for each kind of cooling methods. The resolutions of detector to the characteristic lines of 152Eu under different cooling conditions are studied. The laboratory results indicate that the mechanical cooler (X-Cooler II) is an ideal replacement candidate for the liquid nitrogen cooler that is being utilized by BEMS at BEPC-II. |

Data taking strategy for phase study through ψ′ → K+K− decay

Wang Boqun; Mo Xiaohu; Yuan Changzheng; Ban YongSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The study of the relative phase between strong and electromagnetic amplitudes is of great importance for understanding the dynamics of charmonium decays. The information of the phase can be obtained model-independently by fitting the scan data of some special decay channels, one of which is ψ′ → K+K−. To find out the optimal data taking strategy for a scan experiment in the phase study of ψ′ → K+K− decay, the minimization process is analyzed in detail from a theoretical point of view. |

A Mathematical Review on the Multiple Solublem Problem

K. Zhu; X. H. Mo; C. Z. Yuan; P. WangSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The recent multiple solutions problem in high energy physics has been reviewed with a more mathematical viewpoint. Although previously these multiple solutions are found via fit process, in this letter we have proved that if a sum of two coherent simple Breit-Wigner functions is used to fit the measured distribution, there should be two and only two non-trivial solutions, which are related with each other by analytical formulae. |

On the leptonic partial widths of the excited ψ states

X. H. Mo; C. Z. Yuan; P. WangSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The resonance parameters of the excited ψ-family resonances, namely the ψ(4040), ψ(4160), and ψ(4415), were determined by fitting the R-values measured by experiments. It is found that the previously reported leptonic partial widths of these states were merely one possible solutions among a four-fold ambiguity. By fitting the most precise experimental data on the R-values measured by the BES collaboration, this work presents all four sets of solutions. These results may affect the interpretation of the charmonium and charmonium-like states above 4 GeV/c2. |

Study of the data taking strategy for a high precision τ mass measurement

Y.K.Wang; J.Y.Zhang; X.H.Mo; C.Z.YuanSubjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

To achieve a high precision τ mass measurement at BESIII, two free para-meters (mτ and ε) and three parameters (mτε and σBG)fittings are simulated using sampling technique. For two parameters fitting, two points should be taken, the one is near the threshold of τ+τ- production to determine mτ , the other point is at 3.595 GeV to determine e±ciency. The ratio of luminosity at the two points is 3 to 1. For three parameters fitting, one point should be added at the low energy region with about 10% of the total luminosity. The optimal ratio of luminosity at the other two points is still 3 to 1. |