[en] This calculation shows the existance of tensor-interaction in C-Cbar system. (Author)

[en] A perturbation theory on the basis of spectrum generating algebras is developed. It offers several possibilities for splitting the algebraically formulated problem into an exact solvable one and a perturbation of it. Different conditions for the choice of the corresponding parameters are discussed. The simple charmonium potential V = Z/r + lambdar and the potential of the quadratic Zeeman effect V = -1/r + γ² (x² + y²) are used as examples. Perturbation series with improved convergence properties are obtained. (author)

[en] I discuss a set of observables of large interest for understanding the (soft) hadronisation of partons, in particular the sizable observed polarisations of hyperons and its possible connection to color flow. Further I discuss a set of possible gluon models, in particular the Lund gluon model and its consequences with regard to charm production and possible interpretations difficulties in the calculation of jet cross sections

[en] Rigorous solutions for the one-dimensional quantum mechanical doubly anharmonic oscillator in the form of definite integrals, already presented (Flessas. Phys. Lett. 81 A: 17 (1981)), are here generalised to anharmonic interactions and their interest for models of the charmonium system considered. (U.K.)

[en] When analyzing heavy qq^- states with help of exponential moments we argue that a ratio of moments should be expanded rather than the moments themselves. Within a nonrelativistic approximation we show that the expanded ratio is totally independent on the quark mass definition, whereas the nonexpanded ratio of moments strongly depends on it. (Author)

[en] Logarithmic perturbation theory (PT) for screened Coulomb potential is considered. Calculation of higher PT orders of the level energy E_h is reduced to recurrence relations that are valid for any type of screening and are very convenient for computer calculations. They are employed to calculate the PT coefficient of E_h up to k = 100 for a number of physically interesting cases such as the Yukawa potential, the quarkonium potential, etc. The approach of E_h as k→infinity to the asymptotic form of E_h, defined by the quasiclassical approximation, is discussed. The problem of summation of the divergent PT series is considered. By employing the Pade approximants and the asymptotic form of E_h it is possible to determine with a high accuracy the energy level E(g) for the potentials mentioned above in a range that exceeds considerably the range of applicability of PT, including the strong coupling region

[en] A special coordinate realization of the Lie algebra so(4,2) is used to reformulate the perturbation problem of a hydrogen atom in a linear radial potential over a complete and discrete Sturmian basis. In this way, the Rayleigh-Schroedinger coefficients E/sub N/LM/sup( n/) may be calculated to arbitrarily high order for any state. The large-order behavior of these coefficients is determined by Bender-Wu WKB theory. A general formula for the large-order behavior of the coefficients c/sub n//sup N/LM of the Stieltjes continued-fraction representations of these perturbation expansions is given and related to that of the E/sub N/LM/sup

[en] Recent results on the search for pentaquarks and on charmonium spectroscopy at BABAR are reviewed. The latter includes the observation of the puzzling new state X(3872) → J/ψ π⁺ π^- in B decays, and the searches for X(3872) in two-body B decays and initial state radiation events

[en] In this contribution we review recent results from the BESIII experiment. We focus on two very different main topics. Firstly we report the investigation of XYZ states and the discovery of new charged and neutral charmonium-like structures and then we will present recent BESIII results on studies related to the Collins asymmetries measurement.

[en] In accordance with recent finding of Reinders, Rubinstein and Yazaki we show that for exponential QCD-moments of charmonium the corrections due to dimension six and eight operators are very small so that the ratio of moments used for mass determination remains remarkably stable. (Author)