摘要：实验测量表明体心立方固溶体 约在 2.0 at.% Mn发生相变，但这一相变的机制，相变前后铁锰体系的物理性质变化至今仍不清楚。本文通过密度泛函计算，揭示了这一相变是一种同构相变，并阐明了相变机制和相变前后物理性质的变化。
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：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.
摘要：The technique details for measuring radiation dose are expounded. The results of radiation levels of gamma and neutron are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the radiation level of photon as background for the future experiment is measured by NaI(Tl) detector.
摘要：Multiple solutions exist in many experimental situations when several interfering amplitudes are summed to fit experimentally measured distributions, such as cross sections, mass spectra, and/or the angular distributions. We show a few examples where multiple solutions are found, but only one solution is reported in the publications. Since there is no standard rule for choosing one among the solutions as the physics one, we propose a simple rule that agrees with what has been adopted in previous literatures: the solution corresponding to the minimal magnitudes of the amplitudes must be the physical solution. We suggest test this rule in the future analyses.
摘要：The effects of absolute energy calibration on BESIII physics are discussed in detail, which mainly involve the effects on τ mass measurement, cross section scan measurement, and generic error determination in other measurements.
摘要：By fitting the R values between 3.7 and 5.0 GeV measured by the BES Collaboration, the upper limit of the electron width of the newly discovered resonance Y(4260) is determined to be 240 eV at 90% C.L. Together with the BaBar measurement on Γee• B(Y(4260) → π+π- J/ψ), this implies a large decay width of Y (4260) → π+π- J/ψ final states.
摘要：The theoretical explanations about the "ρπ puzzle" in charmonium decays are reviewed exten-sively, and the comparison of theoretical predications with experimental data is made whenever possible. Three methods to estimate the ratio of the branching fractions of J/ψ and ψ′decays are also discussed. It is pointed out that in order to understand the ρπ puzzle, and the dynamics of charmonium decays, systematic studies should be made in theory, phenomenology and experiment aspects.
摘要：The previous experiments which provide information on the ψ(3770) to non-DD decays are reviewed. Three approaches of searching for the non-D(D) decays are discussed in detail. It is also pointed out that the search for the non-D(D) decays of the ψ(3770) is very important for the understanding of the dynamics of charmonium decays.
摘要：The equivalence of two χ2 forms for linear function fit is proved by mathematical. The simplified R-value measurement are quoted to test the conclusion equivalence.
摘要：Q value, the ratio of charmless hadronic decays between ψ'and J/ψ, is evaluated to be (26.0 +/- 3.5)%. The dependence in evaluation is taken into account carefullyu, and several approaches are adopted to find out the correlation coefficient or covariance between different measurements.
摘要：It is suggested that the newly observed Y(4260) by BaBar Collaboration is a molecular state composed of an ω and a χc1. Both the production and decay properties are discussed. A consequence for this molecular state, Y(4260), is that it decays copiously into π+π-π0χcl. It is also expected that Y(4260) →π0π0J/ψ is produced at half rate as Y(4260) →π0π0J/ψ. These decay modes should be searched for in the B factories using initial state radiative return data and B decay data as well.