Properties of Charmonium States in a Phenomenological Approach

We investigate the spectrum and decay rates of charmonium states within the framework of the non relativistic quark model by employing a Coulomb like potential from the perturbative one gluon exchange and the linear confining potential along with the potential derived from instanton vacuum to account for the hyperfine mass splitting of charmonium states in variational approach. We predict radiative E1, M1, two-photon, lepton and two-gluon decay rates of low lying charmonium states. An overall agreement is obtained with the experimental masses and decay widths.We have estimated the branching ratio of two gluons decaying into light hadrons.     

Study of the XYZ states at the BESIII

With its unique data samples at energies of 3.8–4.6 GeV, the BESIII experiment made a significant contribution to the study of charmonium and charmonium-like states, i.e., the XYZ states.We review the results for observations of the Z_c(3900) and Z_c(4020) states, the X(3872) in e⁺e⁻ annihilation, and charmonium ψ(1³D₂) state, as well as measurements of the cross-sections of ωχ_cJ and ηJ/ψ, and the search for e⁺e⁻→ γχ_cJ and γY (4140). We also present data from BESIII that may further strengthen the study of the XYZ and conventional charmonium states, and discuss perspectives on future experiments.     

Next-to-leading-order calculation in kT factorization

We explain the framework for calculating next-to-leading-order (NLO) corrections to exclusive processes in the kT factorization theorem, taking πγ→γ T as an example. Partons off-shell by k2T are considered in both the quark diagrams from full QCD and the effective diagrams for the pion wave function. The gauge dependences in the above two sets of diagrams cancel, when deriving the kT-dependent hard kernel as their difference. The light-cone singularities in the kT-dependent pion wave function are regularized by rotating the Wilson lines away from the light cone. Both the large double logarithms In2 kT and ln2x, x being a parton momentum fraction, arise from the loop correction to the virtual photon vertex, the former being absorbed into the pion wave function, and the latter into a jet function.     

The effects of time delay on the decline and propagation processes of population in the Malthus-Verhulst model with cross-correlated noises

This contribution presents a derivation of the steady-state distribution of velocities and distances of driven particles on a onedimensional periodic ring, using a Fokker-Planck formalism. We will compare two different situations: (i) symmetrical interaction forces fulfilling Newton’s law of “actio = reactio” and (ii) asymmetric, forwardly directed interactions as, for example in vehicular traffic. Surprisingly, the steady-state velocity and distance distributions for asymmetric interactions and driving terms agree with the equilibrium distributions of classical many-particle systems with symmetrical interactions, if the system is large enough. This analytical result is confirmed by computer simulations and establishes the possibility of approximating the steady state statistics in driven many-particle systems by Hamiltonian systems. Our finding is also useful to understand the various departure time distributions of queueing systems as a possible effect of interactions among the elements in the respective queue [Physica A 363, 62 (2006)].     

类氢U91+离子的辐射复合及其辐射退激发过程的理论研究

基于多组态Dirac-Fock理论方法,利用GRASP92和RATIP以及在此基础上最新发展的RERR06程序,对类氢U⁹¹⁺（1s）离子的辐射复合截面以及辐射退激发过程进行了详细的理论研究.系统地计算了具有确定能量的连续电子被处于基态的类氢U⁹¹⁺（1s）离子俘获到nl （1≤n≤8, 0≤l≤6）轨道形成类氦U⁹⁰⁺（1snl）离子的辐射复合截面,并研究了这辐射复合末态退激发谱的相对强度.研究发现,类氢U⁹¹⁺（1s）离子辐射复合到不同轨道的截面随其主量子数的增大而显著减小;同时,辐射复合末态的退激发对Kα谱线的相对强度有重要影响. 关键词： 辐射复合 多组态Dirac-Fock理论方法 辐射退激发     

A modified implicit Monte Carlo method for time-dependent radiative transfer with adaptive material coupling

In this paper we develop a robust implicit Monte Carlo (IMC) algorithm based on more accurately updating the linearized equilibrium radiation energy density. The method does not introduce oscillations in the solution and has the same limit as Δt→∞$\mathrm{\Delta }t\to \infty$ as the standard Fleck and Cummings IMC method. Moreover, the approach we introduce can be trivially added to current implementations of IMC by changing the definition of the Fleck factor. Using this new method we develop an adaptive scheme that uses either standard IMC or the modified method basing the adaptation on a zero-dimensional problem solved in each cell. Numerical results demonstrate that the new method can avoid the nonphysical overheating that occurs in standard IMC when the time step is large. The method also leads to decreased noise in the material temperature at the cost of a potential increase in the radiation temperature noise.     

漫反射各向异性散射介质内的温度热流场

本文采用射线踪迹结合节点分析法和谱带模型,研究了漫反射不透明边界下吸收、发射、各向异性散射介质内的热辐射传递过程。考虑介质辐射能的入射和散射方向,导出漫反射、不透明边界、各向异性散射介质的辐射传递系数。在辐射平衡的情况下,考察了表面发射率和散射反照率对介质内辐射热流和温度场的影响。研究表明,介质不透明边界处存在温度跃迁现象,而且,内界面发射率越大,相应界面温度跃迁越小。     

管内耦合换热的辐射热流特征及抽样模式比较

通过数值模拟,研究了圆管层流入口段辐射与对流祸合换热中的辐射热流分布特征,提出并比较了采用蒙特卡罗法计算辐射换热的两种抽样模式。结果表明,在圆管入口段的耦合换热中,同一截面的径向辐射热流密度与轴向辐射热流密度数量级相当,世分布形态差别很大。用蒙特卡罗方法计算辐射换热时,采取等权能束的抽样模式,可消除因抽样能束的能量不同而造成的计算误差、降低计算量、提高计算精度。     

Designing Simple Tridentate Ligands for Highly Luminescent Europium Complexes

A series of tridentate benzimidazole‐substituted pyridine‐2‐carboxylic acids have been prepared with a halogen, methyl or alkoxy group in the 6‐position of the benzimidazole ring, which additionally contains a solubilising N‐alkyl chain. The ligands form neutral homoleptic nine‐coordinate lanthanum, europium and terbium complexes as established from X‐ray crystallographic analysis of eight structures. The coordination polyhedron around the lanthanide ion is close to a tricapped trigonal prism with ligands arranged in an up–up–down fashion. The coordinated ligands serve as light‐harvesting chromophores in the complexes with absorption maxima in the range 321–341 nm (ε=(4.9–6.0)×10⁴ M ^?1 cm^?1) and triplet‐state energies between 21 300 and 18 800 cm^?1; the largest redshifts occur for bromine and electron‐donor alkoxy substituents. The ligands efficiently sensitise europium luminescence with overall quantum yields ( ) and observed lifetimes (τ_obs) reaching 71 % and 3.00 ms, respectively, in the solid state and 52 % and 2.81 ms, respectively, in CH₂Cl₂ at room temperature. The radiative lifetimes of the Eu(⁵D₀) level amount to τ_rad=3.6–4.6 ms and the sensitisation efficiency η_sens= (τ_rad/τ_obs) is close to unity for most of the complexes in the solid state and equal to approximately 80 % in solution. The photophysical parameters of the complexes correlate with the triplet energy of the ligands, which in turn is determined by the nature of the benzimidazole substituent. Facile modification of the ligands makes them promising for the development of brightly emissive europium‐containing materials.